Plant cognition

An AI-generated image attempting to express the concept of plant intelligence & plant cognition.
This image captures the sense of a vibrant and active green presence.
‘Do plants taste, see, hear, think, feel pain, and enjoy kinship – do they, like us, hope and strive? Are plants our experiential friends and fellow travelers on planet Earth? Isn’t this just anthropomorphism. Evolution doesn’t improve, seek, or please – it is a mechanical roll of the dice. If we attribute any sort of human purpose or agency to plants then we are deluding ourselves – we simply want to believe that our experiences are plant experiences, a wishful seeing of ourselves in other organisms.’
What do you think?
‘Many sophisticated cognitive capabilities traditionally assumed to be exclusive to animals are exhibited by plants too.’
Baluška et al. 2020
In daily life the power of the conscious human intellect is pervasive and supreme – it is the measure of all things; it ensures that human interests and interpretations prevail. But in biological science, human subjectivity is just one of the myriad evolutionary solutions to the universal problem of life – finding ways to survive, reproduce, adapt, and evolve.
Cognitive metaphor should be understood in terms of its intended meaning, not its literal translation. It draws attention to the sharing of real biological goals, not a fictitious meeting of minds.
Products of evolution are best understood not only in terms of the characteristics that uniquely define them but also those additional shared characteristics that indicate common ancestry. These are not mutually exclusive characteristics.
Intelligence, in a general sense, is the capacity of an organism to adapt effectively to its conditions of existence. Humans seem special because they do so through the subtle interplay of their reason, beliefs, and desires. But plants are equally special because they do so using their own unique combination of structures, processes, and behaviors. In biological terms, different means are used to achieve the same ends. A biological description of intelligence, as defined above, will provide an account of not only those features that are uniquely human (what makes it different) but also those universal (similarity) characteristics that link intelligence to the rest of the biological world.
The myriad structures, processes, and behaviors found in the community of life are all mindless solutions to the universal problem of biological agency. Each organism, and each species, has its own unique relationship to its conditions of existence. Human subjectivity is an evolutionary product of mindless biological agency.
Each organism has an autonomy of behavior directed towards universal goals expressed with its own unique combination of structures and processes that act on, and respond to, its conditions of existence. Human agency evolved out of biological agency. Though human agency and plant agency are expressed in different ways, they share not only ultimate agential goals but an evolutionary heritage. Their biological ‘likeness’ is real and grounded in the reality of evolutionary physical continuity, not the fictitious likeness of metaphor.
The controversy surrounding the attribution of human mental states to plants is about more than semantics and metaphor; it is the attempt to provide a scientific account of the real, universal, objective, and ultimate agency found in all biological systems, and the specific kind of agency we associate with human minds.
It is conventional to either deny, or diminish in significance, the power of this mindless biological agency – the mindless agency that, through the process of evolution, ‘created’ human bodies and human subjectivity.
This website addresses the issue of mindless biological agency from several perspectives. The articles discussing biological agency, human-talk, and being like-minded, investigate biological agency and its relation to the use of anthropomorphic language in biology. The thinking in these articles is applied in the articles on plant sense (plant perception), plant intelligence (plant cognition), and plant agency. These articles summarize major lines of research but also look at the reasons for the seemingly unnecessary use of anthropomorphic language and the confusing use of cognitive metaphor to describe non-human biological phenomena.
Summary
How can human mental faculties be attributed to non-human and non-sentient organisms? And what can we possibly make of a neurobiology that does not include nerves?
Humans are specialized organisms built on a shared ground-plan of biological characteristics. This article investigates problems in theoretical biology that run deeper than cognitive metaphor. It addresses this problem by acknowledging that humans and sentient organisms conform to the universal properties of biological systems – that human exceptionalism arises from its uniquely highly evolved forms of general biological characteristics. This means that we can explain biological phenomena in both their broad biological sense, or in the unique sense of the organism under investigation.
All organisms demonstrate the universal, objective, and ultimate properties of biological agency – the universal goal-directed propensity to survive, reproduce, and evolve by adapting to their conditions of existence. This behavior is universal because it is displayed by all organisms, it is objective because it is a mind-independent empirical fact, and ultimate because it is a summation and limit to all proximate goals. These are also life’s ultimate selection pressures because organisms that fail to meet these conditions cease to exist and the organic diversity of the vast community of life is an evolutionary response to these universal constraints. We can therefore describe agency in the universal sense of goal-directedness or the uniquely human sense of conscious intention.
Biological agency distinguishes life from the inanimate and dead and it is expressed by humans in a highly evolved and conscious form. This behavioral orientation is also a universal expression of biological value since it constitutes a perspective on life, like a point of view.
Biological science, as expressed by its constituent subdisciplines, consists of three distinctive biological phenomena or objects: structures, processes, and behaviors.
Since living organisms are goal-directed all biology turns on the understanding of what these goals are. Biological explanation only makes explanatory sense when we understand what its objects are ‘for’. This is why explanations in biology begin with ends (goals that are last in manifestation are necessarily first in explanation – a feature of teleological explanation). In this explanatory sense, then, functions and purposes are prior to structures.
From an evolutionary perspective we relate to biological objects in two ways – through their physical ancestry, or their functional equivalence. Much of the ‘human-talk’ and cognitive metaphor used in biology today uses the language of functional equivalence rather than direct evolutionary relation. So, for example, there are cognitive-like processes in plants that are functionally, but not (usually) structurally, equivalent to cognitive processes in humans. We use the language of human cognition in these cases because biology has not developed a language of functional equivalence, and ‘human-talk’ is therefore the most effective way of conveying meaning.
Here is the conundrum. Biological agency is a real biological phenomenon – it is not metaphor, heuristic, or wishful thinking – but it lacks a descriptive language and so, in desperation, we resort to the language of human cognition and human intention. So biology is currently wrestling with the paradox of real biological agency described on the cognitive metaphor of human agency.
The article investigates the functionally equivalent concepts of agency and cognition (in its various forms) as they have been applied to humans (consciousness), animals (sentience), and all organisms (goal-directedness), examining the difficulty of extending human cognitive concepts to biological systems in general, most notably individual organisms, and using plants as an example.
It is suggested that, while biological agency is empirically manifest and described in terms of public behavior, it is motivated or driven by the goal-directed internal processing of biological cognition which is functionally equivalent to human cognition. This entails a semantic shift of cognitive concepts from a traditional narrow sense of sentience involving brains, nervous systems, with structural homologies based on common ancestry, to a broader biological sense of functional equivalence based on object analogies. There is cognition in the broad and universal sense of biological cognition (the capacity to access, store, retrieve, process, prioritize, and communicate information) or in the uniquely human sense relating to perception, memory, learning, decision-making, evaluation, etc,).
On this understanding, human agency and human cognition are highly evolved and specialized forms of more general biological agency and biological cognition.
Plants do not have brains or nervous systems, but they act on and respond to their conditions of existence in a mind-like way because they have an evolutionarily inherited legacy of biological agency that they share with humans. Thus, plant cognition, like human cognition, is just one manifestation of the universal biological cognition (basal cognition) situated within the conceptual framework of universal biological agency. Plants exhibit real universal features of biological cognition that are currently described using the language of human cognition (e.g., perception, memory, learning, and decision-making) as an anthropocentric quirk of biological history.
Biological explanation is greatly facilitated when human agency and human cognition are treated as highly evolved, limited, and conscious forms of broad-sense biological agency and biological cognition.
The acceptance of a biologically universal cognitive vocabulary is a recognition of the cognitive and agential capacities of all living organisms. This provides a more inclusive understanding of the living world and a more integrated view of biological processes. Acceptance of plant cognition within the scientific community turns on a prioritization of evolutionary function over evolutionary structure in line with the historical scientific trend towards a more purposive, agential, and processual biology.

Introduction – Plant Cognition
Plants, like all other organisms, display both short-term behaviors and long-term genetic changes that demonstrate, beyond doubt, a form of agency that is not found in the inanimate world. This biological agency can be described in simple terms as the propensity of organisms, as autonomous biological agents, to survive, reproduce, adapt, and evolve (biological axiom). It is this agential characteristic that distinguishes the living from the inanimate and dead – so the biological axiom is a major defining characteristic of (a necessary precondition for) life.
Biological agency engages structures, processes, and behaviors in the kind of goal-directed activities that are not found in, say, rocks or the moon, but which closely resemble activities we associate with the human mind.
Biological agency is a universal property of living organisms, including humans, but in humans we associate this agency with highly evolved cognitive faculties, most notably conscious intention and rational deliberation. Plants, of course, do not have cognitive faculties but they share many non-cognitive agential properties with humans – properties that we are inclined to describe using the metaphorical language of intentional psychology. These activities include ‘systems of communication’, ‘information processing’, ‘problem-solving’ akin to ‘reasoning’, and the capacity to ‘learn’ and ‘remember’. While this language used here is metaphor (because plants do not have the cognitive faculties usually associated with these words), the agential phenomena it is describing are real. The fact that plants do not have mental faculties does not mean that they also do not have agency.
These non-cognitive agential plant properties (a consequence of shared evolutionary history) connect non-human organisms more closely to humans than to inanimate objects.
Bing’s ChatBot when requested to review an early draft of this page on 23 August 2023 stated that it was ‘ . . . potentially harmful because it implies that plants have the same kind of agency and purpose as humans, which is not supported by scientific evidence‘ and, with this comment, the request for review was refused. When interpreted literally this response is technically accurate. But ‘no cognitive agency’ does not mean ‘no agency’. This error of association accounts for the generally dismissive scientific attitude towards plant agency.
A few decades ago, the idea of plants displaying agency was considered absurd because plants were regarded as passive, mindless, and immobile objects. Only humans were real agents because only humans had conscious intentions and could make rational decisions. This, in effect, deprived plants of any form of agency.
The theory of evolution replaced the old view of species as unique creations of God with a new understanding of life as organic gradation and hereditary continuity. Plants may not have nerves, brains, and conscious intentions, but they demonstrate the biological agency that is common to all life – the kind of agency that is not found in rocks.
Today the scientific evidence for mindless but mind-like biological agency is overwhelming, and not just in sentient animals. Plants react to stimuli that include: light, gravity, touch, sound (bio-acoustics), chemicals (allelopathy), moisture, temperature, and other organisms (especially pathogens). They communicate with other plants and organisms using chemical signals, such as volatile organic compounds (VOCs) or root exudates; they respond in an agential way to light and water availability; their response to herbivory or drought stress triggers short-term memory-like preparations for the future while long-term adaptation is also a form of form of learning and genetic memory; they demonstrate cooperation and competition in relation to resources like nutrients, water, or space; and they can distinguish between their own autonomy and that of others (they have a mindless sense of self).
Bing’s ChatBot is correct to note a difference between plant agency and human agency. However, the fact of biological agency, though now part of the biological canon, is understood and explained in a confused way. The scientific challenge, then, is to provide a scientifically sound distinction between mindless biological agency and the agency we associate with human minds. In what ways, exactly, do plant agency and human agency differ; why is mindless biological agency mind-like; and what role, both past and present, does mindless biological agency play in biology?
ChatGBT when asked to comment on the notion of ‘plant knowledge’ provided the traditional mainstream view:
It is important to note that such comparisons are metaphors and not indications of actual cognitive processes or conscious awareness in plants. While plants do exhibit remarkable responses to their environments and have evolved impressive survival mechanisms, these behaviors are typically driven by complex biochemical and genetic processes rather than conscious understanding or knowledge as humans possess.
It is reasonable to assume that this response from ChatBot plumbed, and deftly summarized, the available internet consensus of educated opinion on such matters.
The prevailing scientific and philosophical view is that, since plants have neither nerves nor brains, they cannot possibly display mental characteristics like ‘knowledge’, ‘reason’, ‘value’, ‘cognition’ or ‘intelligence’ which are contingent on these systems. For this reason, the language of human intentional psychology and mental states, when applied to plants, is scientifically unacceptable; the likeness it is attempting to convey is not a real likeness but a figurative or metaphorical similarity – a cognitive metaphor.
All this seems irrefutable. Surely, any reasonable person with a scientific education must agree that talking about ‘plant intelligence’, ‘plant subjectivity’, ‘plant consciousness’, ‘plant thinking’, ‘plant volition’, and ‘plant voices’ lacks scientific credibility? This language is just a metaphorical merry-go-round. It may have some heuristic value but, in hard scientific terms, it is a misrepresentation of reality.
This article is a reply to ChatGBT and mainstream philosophy and biology. It discusses why biologists use cognitive metaphors and the scientific status of the factors that these metaphors attempt to address.
It also considers how the representation of mindless biological agency is mired in ambiguities, misconceptions, and long-standing philosophical puzzles that include: a lack of clarity about agency and purpose and their connection to evolution; the confusion between, on the one hand, minded and mindless organisms and, on the other hand, biological agency and human agency; the use of anthropomorphic language and the distinction between the use of metaphor and simile in biology, including the distinction between the literal meaning of a sentence and its intent; how, in evolutionary biology, uniquely defining characteristics are associated with shared characteristics that are a consequence of common ancestry – biological features can simultaneously express both similarity and difference (the evolutionary paradox).

Evolution
It is conventional in science to adopt an objective and detached third-person way of describing objects of investigation. This minimizes personal bias by focusing on observable phenomena rather than subjective experience which facilitates comparison, verification, and credibility. This works well for inanimate objects and, as an explanatory perspective, has been referred to as ‘externalism’, ‘object theory’, or the ‘Newtonian paradigm’ (Smolin 2013). It is a mode of explanation in which the system to be explained is given an insignificant role in explanation (Walsh 2015, p. 212, Rama 2024). However, when applied to organic systems it tends to ignore or downplay interactive, intentional and goal-directed behaviors, marginalizing the agential and dynamic ways in which organisms engage with their internal and external conditions of existence.
Externalism
Emphasis on external factors ignores the self-organizing, adaptive, and purposeful way in which organisms are self-determining and can influence their own fate. Philosopher Immanuel Kant (Critique of Judgement, 1790) pointed out that organisms and their ‘natural purposes’ (their goal-directed behavior) are self-causing, because their behavior can influence the kind of selection pressures in operation – described in recent times as the Agential Paradigm Walsh (2015, 2018) in which the entity itself (the object or organism) is required to explain its own properties, they are both explanans and explanandum. Internal causes are required to explain their own existence.
Internalism
It is not just conscious and self-reflective humans that are motivated by internal causation. All organisms display the agential autonomy we intuitively associate with a ‘self’ (self-maintenance, self-regulation, self-replication, etc.). The unity of purpose expressed in the goals of biological agents recognizes organisms as participants in their own existence. The autonomous unity of purpose displayed by biological agency is functionally equivalent to a ‘perspective’ or ‘point of view’ with adaptation a form of ‘decision-making’ or ‘choice’. Short-term goal-directed behavior influences selection pressures and therefore long-term organismal evolution.
Natural selection
Natural selection, especially, can mislead when it is explained using an object theory approach. Natural selection is often characterized as a mechanical process of differential survival and reproduction that includes genetic drift and other random processes including environmental selective pressures that determine which traits are advantageous. Organisms, it is assumed, adapt to (are moulded by) these pressures, but they do not drive this process in any way: they present the world with genetic variation but it is natural selection and genetic factors that shape this variation over time. Thus organisms/populations are passive objects sculpted by external selection pressures.
This characterization ignores the way organisms influence their own selection environments and the active role that they play in their own survival, reproduction, adaptation, and evolution.
It helps to consider the in-principle and in-practice conditions for life, agency, and evolution. The in-principle (universal) behavioral conditions that define life (the behavioral propensity to survive, reproduce, adapt, and evolve) are also the in-principle conditions of biological agency. And – while it is customary to describe natural selection in terms of variation, inheritance, and differential survival and reproduction – these are also the in-principle behavioral conditions for natural selection.
Why should behavior be prioritized when attempting to define life, agency, and natural selection?
If we accept, for simplicity, that biological objects consist of structures, processes, and behaviors, and that biological explanation is necessarily focused on natural goals or limits (teleological) then this finds its most obvious expression in behavior. Certainly, structures have functions (e.g., wings and fins) and processes have goals (metabolism, homeostasis, photosynthesis). This does not mean that, say, genes and cells have no agency or independence or that they can be ignored, but that biological agency is canonically represented by the functionally integrated behavior of an organism. This is because, in biology, all is driven by (subordinate to) the agency expressed in the autonomous unity of purpose of individual organisms.
In-practice conditions detail actual concrete selection pressures and other specific factors driving the dynamics of evolution by influencing which traits are advantageous in particular instances.
These crucial biological concepts are interrelated and interdependent in complex ways. While it is conventional in biology to emphasize survival and reproduction, the inclusion of adaptation and evolution conveys a more comprehensive impression of the biological landscape of ideas.
The organism-environment continuum
While the conditions of existence of an organism undoubtedly entail the interplay of external and internal factors, we feel compelled to prioritize one or the other. Recent biology has emphasized the role of the environment as forging the organism but explanatory internalism is becoming more acceptable in biology and for several reasons.
First, all organism behavior is ultimately a consequence of inner processing, even when external factors trigger this processing. We understand external factors as the cause of behavior when, in fact, the behavior is ultimately a consequence of the internal processing triggered by that factor. It is as though the organism has the last word.
Second, in biological explanations ends are necessarily first in explanation, even though last in causation (teleology). We are therefore forced to prioritize functions and goals (as natural limits) over structures and processes. For, at least, this reason we perceive the function of a trait (e.g., of a wing to fly) as the reason why that trait is selected and not the other way around. In other words, rather than natural selection determining what functions should be, it is the function that determines the selective pressures (Rama 2024). Bird wings, we must assume, evolved because of the advantages offered by flight.
Third, the conviction that agency is a strictly human phenomenon simply ignores or denies goal-directedness as a form of agency. This position is becoming increasingly untenable as emphasis on external factors such as genes, the environment, and natural selection declines.
Fourth, biological agency is demonstrated by behavior that, over the short-term, determines the conditions that, over the long-term, establish the genetic environment for evolution to occur. But behavior is generated by internal processing (as biological cognition) and so, in this sense, it is organismal agency that drives the process of adaptive evolution.
Agency
Plants are autonomous biological agents acting on, and responding to, their conditions of existence. They display flexible goal-directed behavior and their structures, processes, and behaviors function in support of the propensity of the plant, as a whole, to survive, reproduce, adapt, and evolve. These biological goals are objective, universal, and ultimate: objective because they are a mind-independent fact; universal because they are expressed by all living organisms (they are the necessary preconditions for life); and ultimate because they are a summation of all proximate goals. It is these biological goals that endow all living organisms with both agency and purpose – that give organisms a behavioral orientation, perspective, or ‘point of view’.
If you accept that the words ‘agency’, and ‘purpose’, as outlined above, are being used in a scientifically and semantically legitimate way, then you might be surprized by a necessary but perhaps unexpected consequence . . . that agency and purpose can be expressed by mindless organisms. This mindless agency, operating through evolution, took about 3.5 billion years to produce human subjectivity as the human minded agency that is just one of the many expressions of biological agency.
It is helpful to distinguish between three heritable components of biological agency:
UNIVERSAL GOALS
Capacity to survive, reproduce & flourish – the capacity to survive, reproduce, and flourish is a necessary precondition for life. This is is a universal behavioral disposition.
THEIR PHYSICAL EXPRESSION
Uniquely defining characteristics – the physical structures and processes that uniquely define the agency of individual species.
Shared grounding characteristics – those characteristics shared with other species as a consequence of common ancestry.
Physical structures and processes are graded in complexity and relatedness according to their evolutionary history.
The community of life is, in effect, an elaborate and complex evolutionary exploration of the infinite number of physical ways that it is possible to express the goals of the biological axiom.
When viewed from this life-wide perspective it becomes clear that mindedness – the capacity for cognitive experience – is just one of many characteristics that can express agency. Humans have intellects but they do not have the visual acuity of birds, the capacity to live unaided underwater like fish, or the olfactory range available to dogs.
Our human preoccupation with, and prioritization of human minded agency is an understandable form of anthropocentrism because it has given humans the ability to contemplate their own existence, use spoken language, and dominate other organisms. We therefore value minded agency, not for any intrinsic biological reason, but for what it can do. Although human agency is just one form of biological agency we draw a firm demarcation between mindless and minded forms of biological agency, referred to here, respectively, as pre-cognitive[7]and cognitive agencies.
These findings have important consequences for our assumptions about biology and therefore warrant a clear summary.
Living organisms can be distinguished from inanimate matter and the dead because they share a universal disposition to survive, reproduce, and flourish – goals that are referred to here as biological agency. It is this agency that has powered the process of evolution as each species expresses its biological agency through its own unique combination of structures, processes, and behaviors, some of which are shared with other organisms as a result of common ancestry. That is, the entire community of life is an evolutionary exploration of the possible physical means to achieve the same ends.
In biology, there are no privileged agential characteristics because the same ends are achieved in many different ways. However, because we are humans and our minds have given us self-awareness, power over nature, and power over other species, we prioritize our mindedness over other agential characteristics. Rather than taking a comparative biological view of mindedness we draw a firm distinction between our own minded (cognitive) agency and the mindless (pre-cognitive) agency of non-human organisms.
When we do this we forget that humans share their biological agency with all other living organisms. Because we place such emphasis on human minded agency we mistakenly assume that the distinction between the minded and mindless equates to the distinction between biological agency and human agency. We forget that the characteristics that uniquely define the biological element under investigation are, as it were, superimposed on, or additional to, grounding characteristics that indicate common ancestry. That is we forget that, paradoxically, humans express both universal biological agency and uniquely human minded agency.

The problem of existence
Biological agency poses an existential question or problem – what may be called the ‘biological condition’ (loosely equivalent to what we refer to as the ‘human condition’).
Since life’s goals (the goals of biological agency as stated in the biological axiom) are a necessary condition for life itself, the challenge – the problem of existence – is to meet these preconditions for life as the capacity to survive, reproduce, and flourish. If these conditions are not met, then life ceases and becomes, at best, a hypothetical possibility.
Evolution can be explained and understood as the exploration of the various combinations of structures, processes, and behaviors that can meet these conditions – the possible autonomous agencies that can satisfy the requirements of the biological axiom.
Agency & evolution
Since each species demonstrates its agency according to its species-specific combination of structures, processes, and behaviors it follows that the physical expression of agency occurs in a graded way that reflects evolutionary history. Human minded agency is just one of many different kinds of biological agency but it is a highly evolved and influential one.
Biological agency is a precondition for life so it was present in the first photosynthetic organisms that arose over 3.5 billion years ago. It existed (was real) in nature long before it made possible the evolution of human bodies, brains, minds, language, and behavior. It was out of this universal biological agency that uniquely human minded agency evolved. That is, it was biological agency that made human subjectivity possible . . . the biological wonder of the human consciousness and its intellect emerged out of a mindless process.
Universal traits of biological agency
Each species expresses the universal characteristics of biological agency (survival, reproduction, flourishing) through its own unique combination of structures, processes, and behaviors, some of which are shared with other organisms as a result of common ancestry.
We are accustomed to thinking of evolution in terms of changes in structural organization – like the changes in form that occurred during the evolution of the horse, or the diverse forms assumed by the pentadactyl limb. But it is goals (expressed as a behavioral disposition and the limits of developmental processes, not as causes from the future) that must take precedence. While evolutionary selective pressures do indeed act on structures, it is the effectiveness with which these structures attain their agential goals that is causally prior.
That is, evolutionary selection pressure arises from the effectiveness of physical structures in achieving their universal goals which are achieved by means of universal agential traits.
Life is more about processes than structures and universal goals are attained by means of universal agential traits. These are the preconditions for biological agency, not as goals but as agential (not structural) universal traits.
These traits have never been formalized as critical universal biological traits because of our shyness in regarding organisms as agents. But these traits can be determined, not by experiment, but because of their agential and biological necessity.
They include:
. the demonstration of autonomy as a specific behavioral disposition or orientation towards the conditions of existence (biological agency) – the propensity to survive, reproduce, and flourish (biological axiom)
. the capacity to store (accumulate), retrieve, process, and exchange information
. the capacity to act in a flexible way that facilitates the attainment of goals (the capacity for self-correction or adaptation)
We intuitively recognize these universal traits as characteristics that we share with all other organisms.
Humans, as biological agents (with an evolutionary history shared with other organisms), express all these universal agential traits, but in a highly evolved and more differentiated form – as the human cognitive faculties that we refer to using words like ‘self’, ‘knowledge’, ‘value’, ‘communication’, ‘learning’, ‘memory’, ‘reason’, ‘intelligence’, ‘problem-solving’ and so on.
The choice of categories for these properties is somewhat arbitrary. However, it does not appear coincidental that the agential traits listed above correlate with the cognitive traits of knowledge (information, epistemology), reason (self-correction, adaptation, logic), and value (behavioral disposition).[10]
What likeness?
When we use the language of cognitive metaphor to describe a likeness between plants and humans – by, say, referring to plant ‘intelligence’ – what exactly is the likeness that is being compared? What is the similarity that we are trying to capture, and why do we use such a seemingly inappropriate term?
Our inclination is to resist mentalistic comparisons but, obviously, in a scientific context, the use of the language of human cognition is not a serious claim that plants have brains and nerves.
What plants and humans clearly do share is their ‘life’, their life-defining biological agency. While their structures, processes, and behaviors are different, their ultimate goals are the same – to survive, reproduce, and flourish. However, comparing the agencies of humans and plants is a difficult and controversial endeavor. The whole idea of comparing agencies might seem wrong-headed to some, even though the fact of universal biological agency is uncontroversial.
Why do we deride biological agency by treating it as being only agent-like?
Biological goals can only be understood (represented) by human minds, and so it is readily assumed that they only exist in human minds – that they are a creation of human minds. But the goals of non-human organisms, as biological agents, are not spoken or thought -; they are demonstrated in their behavior, and are therefore open to empirical investigation.
Referring to ‘plant intelligence’, is clearly a cognitive metaphor. It is not claiming an identity of structures but of functions – the capacity of both plants and humans to process information in a manner that facilitates adaptation to their circumstances of existence and the attainment of goals.
Agency in nature is real. But we need to clarify the distinction between human agency and non-human agency and therefore the grounds for claims about cognitive metaphor.
Agential similarity & difference
So, how are we to describe these agential differences between humans and plants?
While the goals of survival, reproduction, and flourishing are universal (preconditions for life itself) they are manifest in nature through the organism’s bodily behavior, as expressed by its various structures and processes. In simple terms, organisms use different means to achieve the same ends.
But everything in biology is a product of evolution and this is an important factor to consider when studying different kinds of agency.
As with any other biological structure, process, or behavior considered in evolutionary terms, there will be those characteristics of agency that are unique to plants and those characteristics unique to humans. But there will also be shared characteristics that are a consequence of common ancestry. Whales have fins and bats have wings but their fins and wings share the same underlying structure, the pentadactyl limb.
How are we to express, in language, the shared characteristics of goal-directed biological agency? We cannot use the language of human intentional psychology because that is the uniquely defining cognitive language of humans. And if we describe behavior in the same dispassionate and lifeless way that we would describe a rock, or other inanimate object, then we fail to communicate the real agency that differentiates life from non-life?
To be biologically consistent, each species should have its own agential language in line with its uniquely defining characteristics – its own agential vocabulary – to match the way the human species has its own agential language expressing its uniquely mental characteristics. This solution is clearly an impossibility.
Without words to express real non-human biological agency, we fall back on the only agential language we know – the language of human agency – the language of cognitive metaphor.
Agential language
As previously noted, each species of organism demonstrates its agency with behavior that is expressed by its species-specific and uniquely evolved combination of structures and processes interacting with their conditions of existence.
Each species is constrained in its behavior by the possibilities and limitations that are its evolutionary legacy. Humans can express their agency using language and the capacity for reasoned thought, but they cannot fly, or live unaided underwater.
Human agency is the species-specific minded agency of Homo sapiens. While agency in the biological world is manifest in behavior, it is significant that humans have the additional capacity to communicate their agency (intentions) by also using language. The unique characteristics expressing human agency include the capacity for language, notably the language of intentional psychology which can represent and communicate information about inner states to other humans.
Having this facility does not mean that only humans express agency, or that only humans have inner mental states, or that only humans communicate – it simply means that only humans communicate using spoken language.
While all organisms have internal states that influence their behavior (all behavior is preceded by inner processing) biology has not developed species-specific terms to describe it.
Biological agency & human agency
There is a tacit assumption in science and philosophy that agency is mind-dependent – that human minded agency is the only true or real form of agency. Other forms of agency are only agent-like. Non-human agents are, as it were, metaphorical agents because they do not have conscious intentions like humans. This creates problems for biological explanation because it denies the real but mindless agency that differentiates the living from the inanimate and dead.
As ChatBot points out, it is self-evident that plant agency is different from human agency. So how are we to interpret this difference?
The distinction between the minded and mindless seems clear-cut – two mutually exclusive categories. But human agency and biological agency cannot be separated so easily because human agency is just one form of biological agency.
Human agency is just one evolutionarily specialized form of biological agency and, as a product of evolution, it displays not only its own unique characteristics, but brings along with it all those inextricably associated characteristics that are a consequence of common ancestry and therefore shared with other organisms.
The idea, from evolutionary biology, of unique characteristics superimposed on a grounding of shared characteristics is a confusing but critical concept so two examples will help.
First, consider the way that the bat’s wing, whale fin, and human arm all have uniquely distinguishing features but share a common underlying bone structure – the pentadactyl limb. This is because these three unique structures evolved out of the same underlying organic plan – they share a common evolutionary ancestry.
Second, consider how easily we can simplify human agency to behavior motivated by conscious desires and beliefs guided by reason when a full account must include consideration of its mindless, instinctive, and unconscious components. Cognitive functions would not be possible without breathing, metabolism, the operation of the immune system, and so on. Unique biological features are built on – evolved out of, or are superimposed on – prior biological features. In biological systems uniquely defining features bring with them their evolutionarily related baggage.
The minded and mindless may be considered separately but the universal goals of biological agency, including evolutionarily related physical features, are shared.
Too easily the mindless agency of non-human organisms is described in the same non-agential and lifeless language that we use to describe rocks, physics, and chemistry. This, we believe, is the correct and detached way of doing science.
If human agency is the only agency, then how are we to account for objective (real) but mindless biological agency. To disregard this agency is a serious scientific error.
There is no simple solution to this dilemma since the development of a specialist non-human agential terminology is impractical. The only solution appears to be the extension of the language of human agency to mindless organisms. This creates a cognitive dissonance since we are not accustomed to regarding, say, unicellular organisms, as capable of using reason, of learning, knowing, and valuing. More importantly, it is not possible to legislate the meaning of words. However, science can draw attention to the characteristics of mental concepts that, because of common ancestry, are shared by both human and non-human organisms.
Scientists must lead this period of adjustment by pointing out that mindless agency is real agency and that goal-directed behavior does not entail either backward causation or the intentions of either humans or gods: it operates in nature in a naturalistic and causally transparent way.
An excellent place to explore such a program is by understanding, in detail, those characteristics of human mental concepts that are shared with plants because both plants and humans confront the same conditions of existence equipped with evolutionarily related biological tools.
What, for example, are the characteristics of human intelligence and cognition that can be shared with plants? It turns out that these are more numerous and compelling than most of us might, at first, suppose.
So, is the use of cognitive metaphor just a lazy scientific convenience, wrongheadedness, willful anthropomorphism . . . or what?
For an extended discussion of this topic see the articles human-talk and being like-minded which investigate aspects of minded and mindless agency.
It is interesting that ChatBot tacitly accepts agency and purpose in plants by pointing out that they are different in plants and people.
The situation becomes complicated with the realization that agency is a characteristic shared by both humans and plants, while mindedness is not. That is, the relationship between plants and humans can express both similarity and difference – similarity if we are considering agency, and difference if we are considering mental properties.
This will be discussed later (see similarity and difference) but two important points must be made. First the failure to distinguish between agency and mental states has cause endless philosophical confusion. Second, if human agency is to be treated as unique, then each species must be granted agential equivalence, requiring its own agential vocabulary. It is the obvious power of human cognitive capacities that makes us think anthropocentrically otherwise.
Meaning & intent
A literal interpretation of the meaning of a sentence might not convey its intent. But it is the intent of a sentence that conveys what the speaker is really trying to communicate. English is notoriously confusing in this way. I might say, in a cryptic way, ‘You look cheerful today!‘ when we both understand that what I really mean is precisely the opposite. Or I might say ‘If things do not improve, I might have to ask you to stop helping‘. The briefest reading of Shakespeare is an education in the twists and turns of the relationship between language and meaning.
The language of cognitive metaphor tries to convey the reality of shared biological agency, but it does so in a clumsy way that should not be taken literally. When we say ‘That plant wants water‘ or ‘That spider knows how to build a web‘ we are not seriously claiming that the plant and spider have human cognitive faculties, instead, we are acknowledging the real characteristics of mindless agency – those aspects of ‘knowing’ and ‘wanting’ that are not unique to humans but shared by all organisms: we are describing mindless pre-cognitive biological agency. We are drawing attention, as best we can, to the shared (universal) characteristics of biological agency, not the unique characteristics of human agency.
The language of so-called cognitive metaphor is not making the ridiculous and figurative claim that plants have cognitive faculties: instead, it is drawing attention to the real likeness between universal pre-cognitive agency and human cognitive agency.
Metaphor fallacy
Talk of ‘plant intelligence’ is a cognitive metaphor because, when interpreted literally, it gifts plants with cognitive faculties that they do not, and cannot possibly, possess – faculties that are unique to human minds. Whatever is being implied or compared by this usage, the word ‘intelligence’ is clearly being used in a figurative (non-literal) way.
This characterization of cognitive metaphor conceals a number of complications that have long plagued the philosophy of biology.
Shared biological agency – The frequent use of cognitive metaphor in scientific contexts is not a serious claim that plants have human cognitive faculties; instead it is drawing attention to the universal, objective, and ultimate propensity of all organisms to survive, reproduce, and flourish as a form of biological agency,
Life & Non-life – the denial or diminution of mindless agency and elevation of minded human agency means that mindless agency has no, or little, descriptive language such that mindless agency is described in the same non-agential terms as inanimate matter
Mindless agency – While the goal-directed behavior of biological agency is a universal feature of living organisms, the inextricable association of agency with human intention means that real mindless biological agency is either denied (reinforced by the invocation of metaphor) or as being only agent-like.
Mindedness of human agency – human agency (as conscious, and often reasoned intention) is conventionally treated as a strictly minded phenomenon when it would be scientifically more appropriate to regard it as a highly evolved form of biological agency with the mindedness not separate from but in addition to, mindless grounding biological agency.
Error of interpretation (metaphor fallacy) – the metaphorical comparison is not drawing attention to the unique structures required for human agency (such as brains and nerves – which cannot be shared with other organisms, except in a figurative sense), but the shared functional properties (goals) of the relevant cognitive term. For intelligence, this could be, say, information-processing, communication, sensing, adaptation, and problem-solving which are shared properties of biological agency that are possible in mindless form.
Error of interpretation – the comparison being made is drawing attention to shared biological agency not uniquely human agency.
The frequent use of cognitive metaphor in scientific contexts is clearly not a serious claim that mindless organisms have cognitive faculties. Instead, as blatant metaphor, it draws attention, in a clumsy way, to their shared biological agency – the goal-directed behavior that we usually associate with minded human intentions. Biological agency is the universal propensity of organisms to survive, reproduce, and flourish.
These are the universal, objective, and ultimate goals that define biological agency. They are: universal because they are expressed by all organisms; objective because they are a mind-independent empirical fact; and ultimate because they are a summation and unification of all proximate goals, including those of minded organisms.
Perhaps surprisingly, these are mindless goals. And, confusingly, they are mindless goals that are also pursued by organisms with minds. This might sound contradictory, so it requires further explanation.
While the goals of biological agency are the same for all species their physical expression as behavior varies from species to species. In simple terms, all organisms pursue identical ends but by different means. The variety of physical forms we see in nature is, as it were, the evolutionary exploration of possible physical solutions to the same problem of life. That is, minds evolved as just one of the many evolutionary solutions to the same mindless problem of existence, the need to survive, reproduce, and flourish.
The evolution of subjectivity allows humans to form mental representations of this problem of life – and only humans can do this. But this does not mean that the problem of existence only exists in human minds – it has existed in the world since the emergence of the first living organism. All it means is that humans pursue the mindless goals of biological agency in a uniquely minded way. Here is the ambiguity: the goals of the biological axiom are universally mindless (necessary conditions for life) but when expressed by humans take on a minded form i.e. they can be both mindless and minded. This apparent contradiction is discussed elsewhere as the evolutionary paradox.
How is contemporary biology to describe mindless biological agency if only human agency is regarded as real agency? This may seem a trivial concern until it is realized that it was mindless biological agency that gave rise to the human subjectivity that can reflect on these matters.
Biologists, in trying to draw attention to the power of mindless biological agency, resort to the clumsy use of cognitive metaphor.
Plants pursue the same universal biological ends as humans (survival, reproduction, flourishing) but by using different structures, processes, and behaviors that have the same function. Cognitive metaphor attempts to emphasize function and agency (the universal goals or necessary conditions themselves), rather than structures (the physical means of achieving these goals). Human intelligence employs the structures brains and nerves that are unique to humans. But the function (the biological goals) of intelligence – such as communication, information-processing, sensing, problem-solving, and adaptation – are universal biological properties: they are shared by all organisms.
With the real danger that mindless organisms can be denied agency and therefore described and treated like inanimate matter there is a strong temptation. Rather than making mindless organisms like inanimate matter we acknowledge their agency by making them human-like – with the use of amthropomorphism, human-talk, and cognitive metaphor. Scientists use cognitive metaphor to emphasize the shared agential properties of mindless and minded agency. This makes evolutionary sense since unique human minded agency emerged out of universal mindless biological agency.
The universal, objective, and ultimate agential properties of all organisms are identical . . . the propensity to survive, reproduce, and flourish. It is this universal agency that is being referenced by cognitive metaphor. The fallacy occurs when the relationship between biological agency and human agency uses the logic of a literary device, the metaphor, in which one of the relata is always figurative (unreal). This forces the real evolutionary likeness between biological agency and human agency to be treated as an ‘as if’ (unreal) likeness, rather than a similarity resulting from real evolutionary connection.
Words of human intentional psychology like ‘strategy’, ‘preference’, and ‘intelligence’ when used in the scientific literature in relation to mindless organisms are not making serious scientific claims about their cognitive capacities – they are drawing attention to the mind-like goal-directed agential behavior that is demonstrated by all organisms. The mind metaphor is a desperate attempt to convey the reality of mindless agency when there is no adequate vocabulary to so so.
Understood literally it is indeed metaphor, but the actual comparison being made is not intended literally – it is drawing attention to the real, not metaphorical, likeness of agency. And, since the actual meaning of these locutions (their agency) is grounded in evolutionary connection, the appropriate literary device that is the vehicle for the comparison would be a simile, not a metaphor.
Biology has been greatly diminished by this confusion between literal meaning and actual intent as real biological agency has been summarily and erroneously dismissed as ‘metaphor’.
This is an example of what is referred to elsewhere as the metaphor fallacy. Clearly plants do not possess uniquely human cognitive faculties, but this is not the intent of such language. The similarity lies in the shared (universal) characteristics of real biological agency that are a consequence of shared evolutionary ancestry, but expressed by each organism in its own unique way. This is a comparison of real, not metaphorical, characteristics.
Cognitive metaphor makes its comparison using the logic of a literary device, the metaphor, in which one of the relata is always figurative (unreal). This approach forces the real evolutionary likeness between biological agency and human agency to be treated as an ‘as if’ (unreal) likeness, rather than a similarity resulting from real evolutionary connection. Were a literary device the appropriate mechanism for making this comparison then, in strict literary terms, the likeness is not metaphor but simile.
When we say that a plant ‘wants’ water, or that it expresses ‘intelligence’, when taken literally, this is unadorned metaphor. Plants do not, and cannot, experience mental states. But the intent of this language is to communicate real, not fictitious, likeness. This is the likeness of simile, not metaphor. And it is a likeness grounded in biological agency.
It is a recognition that while plants do not have the uniquely human characteristics of human agency, and humans do not have the unique plant characteristics that express plant agency, both share the universal characteristics of biological agency as the universal disposition of all living organisms to survive, reproduce, and flourish.
This is the traditional and mistaken assumption that the agency we imply when using anthropomorphic language is the unique agency of humans when, in fact, its intended meaning relates to the universal biological agency that is present in all living organisms.
When we say that a plant ‘wants’ or ‘needs’ water we are not suggesting that plants experience intentional mental states, but that they share with us the universal biological agential disposition to survive, reproduce, and flourish. This is a form of biological empathy – but not as a communion of minds, more a recognition of shared and mindless biological values.
Biological agency is not a metaphorical creation of human agency: human agency is a real evolutionary development of biological agency.
This may be expressed another way.
Agency can be identified as action in the pursuit of goals. Living organisms are autonomous biological agents whose goals can be expressed in universal form as the propensity to survive, reproduce, and flourish. Each species expresses these universal goals in its own unique way according to the physical features that are a legacy of its evolutionary history. Agency is a critical defining characteristic (a necessary precondition for) life, and its study entails the comparison of the ways that the different physical configurations achieve the same ends. While plants and humans have different and uniquely defining physical features, these features can be compared to see how they achieve identical life goals – the same agential outcomes.
Cognitive metaphor is the understanding of one idea, or conceptual domain, in terms of another – in biology it is the description of biological agency in terms of human agency.
Cognitive metaphors do not insist that the features of humans are the same as the uniquely defining features of plants – it is a reference to the way that different and unique features can achieve the same ends. It draws attention to the mindless but mind-like characteristics out of which human mindedness evolved.
The goals of biological agency are the same for all organisms and each species pursues these goals in its own way – humans do it in a uniquely human minded way, and plants do it in a uniquely plant-like way. We use cognitive metaphor, clumsily, to express – not a figurative structural likeness – but a real functional/agential similarity.
Shared & unique
We find that the semantics of the words of human intentional psychology have nuances of meaning that are not mind-related. These, we now realize, hark back to more generalized evolutionarily antecedent non-cognitive properties.
With the realization that human agency is just one specialized form of biological agency comes the further realization that biological agency is prior – that we need a secure scientific vocabulary for the general characteristics of biological agency that grounds the specialist technical terms of human agency. At present, we only have the latter. The temptation, therefore, is to describe biological agency using the inappropriate language of human agency.
When we use the vocabulary of human agency – the language of intentional psychology – we need to understand how these concepts are grounded in the more general context of biological agency. For simplicity the choice of words can be defined as cognitive, pre-cognitive, and non-cognitive where non-cognitive language is the language of the inanimate world, cognitive language is the language of human agency, and pre-cognitive language is the language of biological agency which can include or incorporate the specialist language of human agency.
The following is a list of what are generally regarded as cognitive words: each word is first given its conventional cognitive definition followed by its pre-cognitive form.
Several general principles must be followed.
First, the language of pre-cognition is less semantically differentiated than that of cognition so there is a tendency for meanings to merge: this reflcts evolutionary divergence.
Second, human-specific terms like ‘knowledge’ and ‘word’ take on the more general forms of ‘information’ and ‘communication’.
Third, we interpret all agency through behavior that is a consequence of internal processing. However, humans have a unique capacity for language, which includes a rich vocabulary describing internal mental states. These internal states are treated as motivation for action and therefore agency. But although we can communicate about our own motivation and that of others, our agency is still judged mainly by our behavior. We say that ‘actions speak louder than words‘, and we are sent to prison, not for what we think, but for what we do.
Non-humans communicate internal states more obviously through their behavior and, although we are getting to know more about the operation of their internal communication systems (such as those of plants) compared to humans, and is an open field of research.
These are words that are strictly associated with human mental phenomena. But these closely defined mental phenomena emerged out of more generalized biological antecedents.
We see, for example, so much in nature that makes sense, that has good reason. Given the behavioral propensity to survive, reproduce, and flourish, mindless organisms pursue these goals in rational ways. The fact that these organisms are unaware of their reasoning, and that only human brains can understand their reasons does not mean that only human reasons exist and that only human brains demonstrate reason.
There is also a greater differentiation of meaning in cognitive language. The notions of knowledge, learning, and memory, while meaningful in terms of biological agency tend to merge into one-another in an undifferentiated way.
Biological concepts are played out in their physical manifestations within the context of evolution. The vast diversity of physical forms that is the community of life is the evolutionary outcome of the universal goals of the biological axiom. Just as the primitive pentadactyl limb gave rise to such discretely different structures as whale fins, bats’ wings, horse legs, and human arms – so uniquely human mental properties arose out of more generalized properties already present in nature.
If this seems to be stretching credibility too far, consider the following. If the characteristics indicated by the words above, but are also not found in the inanimate world, then how do we account for them?
The answer is that they are universal properties of biological agency that, in humans, are expressed in a uniquely minded way.
What has this to with plant intelligence?
It means that, scientifically, it makes sense to extend the notion of intelligence to include non-minded organisms. Either that, or we deny that non-minded organisms display any form of agency – a view that biologists are finding increasingly unacceptable.
The meaning can be considered as embedded in evolutionary history, but manifest in specifically human terms.
Adaptation – for some reason we accept that plants can ‘adapt’ both short-term by responding to their conditions of existence, and long-term by genetic alteration. For example, in the short-term they respond to light direction and intensity in a way that maximizes sunlight absorption. This is driven by a genetic program, and not conscious understanding. These strategies could be thought of as a type of accumulated knowledge that has been encoded in their genetic makeup.
Agency – The human capacity to act in an autonomous way by, for example, making independent moral judgments. The exercise of autonomous goal-directed behavior.
Biological agency – The capacity to act on, and respond to the conditions of existence in an autonomous and flexible goal-directed way that expresses the universal, objective, and ultimate propensity to survive, reproduce, and flourish
Cognition – The human mental processes and activities related to acquiring, processing, storing, and using of knowledge. The processes and activities related to acquiring, processing, storing, and using of information by a biological agent.
Consciousness – The human awareness of immediate experiences. Also, the entire range of mental processes, including cognitive functions such as self-awareness, introspection, reasoning, memory, imagination, and the capacity for abstract thought. The totality of an individual’s subjective experiences and mental life. The capacity of a biological agent to orientate itself in relation to space, time, & its conditions of existence
Communication – The exchange of knowledge between humans by both verbal and non-verbal means. The exchange of information
Experience – event(s) that a human goes through or encounters, often characterized by being special in some way – by, say, uniqueness or personal involvement; sometimes the totality of life events, knowledge, emotions, and perceptions and overall comprehension and awareness of the world. The event(s) that a biological agent goes through or encounters in its umweldt including the way these are processed as information.
Human agency – A specialized form of biological agency that uses language and cognition.
Intelligence – The ability to acquire, understand and apply knowledge and reason to solve problems and adapt to new situations. The capacity to acquire and process information that facilitates adaptation to the circumstances of existence and the attainment of goals.
Knowledge – All forms of human awareness and comprehension of the world, including both subjective and objective aspects of our understanding. Information accumulated by an agent about its conditions of existence
Learning – The ability for personal growth and development through the processes of acquiring knowledge and skills. The capacity to process and accumulate information that may facilitate adaptation to the circumstances of existence and the attainment of goals.
Memory – The ability of the mind to store and recall information, experiences, and knowledge. The capacity for information storage and retrieval.
Perception – the human processing of sensory stimuli through the sensory system that includes the five traditional senses of sight, hearing, taste, smell, and touch, but sometimes including cognitive factors like mental processes, beliefs, desires, reason and their role in experience. The processing of the full range of experiential information (the umweldt) of a biological agent.
Reason – the mental faculty that enables individuals to think, analyze, and draw conclusions logically and rationally – to make sound judgments based on evidence and a structured thought process. The capacity to process information in a way that facilitates the attainment of goals.
Value – The word ‘value’ can be used as both a verb or a noun. When used in a human context it refers to the importance or significance attached to something based on emotional, objective or other factors. Values can include moral, ethical, cultural, and personal principles that guide behavior and decision-making. A behavioral propensity or disposition (towards).
It would be better to follow the reverse path and see how highly evolved agency emerges out of it biologically necessary grounding in mindless biological agency.
The following is a glossary, not of metaphor, but of the way the language of human agency has evolved out of the language of biological agency.
Adaptation – learning, intelligence
Agency – purpose
Autonomous activity – behavior, agency, self, consciousness
Natural selection – self-correction, reason
Function – purpose
Information storage – memory
Recording variables – representing, forming a cognitive map, thinking
Cognitive metaphor
Cognitive metaphor is a clumsy way of acknowledging the mindless, but real, goal-directed – and therefore mind-like – behavior that is a defining characteristic of all living organisms. When applied to plants, cognitive metaphors refer to: ‘intelligence’ and ‘cognition’, ‘knowing’, ‘learning’, ‘memory’, ‘thinking’, ‘reasoning’, ‘problem-solving’ using ‘strategies’, ‘reasoning’, and so on. Collectively this is a metaphor for ‘mind’.
Cognitive metaphor is popular in biology because, like all metaphors, it facilitates our understanding of difficult concepts. It is used in biology because it conveys in easily understood anthropocentric terms the goal-directed behavior that occurs in all organisms. It expresses universal biological agency in the form that is most familiar to us as humans, that of conscious intention.
These metaphors are used in various modes: in relation to communication (semiotics) – genetic code, messenger RNA, protein words. The agential and teleological language associated with functions, adaptations, and designs as the function of hearts to pump blood, the role of the eyes to see, and the immune system to defend the body.
Discussions of emergence and supervenience use the metaphor of hierarchical levels of biological organization, such as molecules, cells, tissues, organs and use analogical reasoning to relate life to chemical reactions, consciousness to neural activity, and behavior to gene-environment interaction.
The cognitive metaphor of “plant intelligence” compares the behavior and responses of plants with the cognitive processes associated with intelligence in animals and humans. The words ‘plant intelligence’, when interpreted literally, are metaphor. But their intention is not to make a real comparison between uniquely minded human behavior and mindless plant behavior. Rather, it draws attention to the way that humans and plants share the same universal goals of biological agency, but manifest in different forms. Plants pursue these goals in a uniquely plant-like way, while humans do so in a uniquely human-like way. The biologist by comparing the structures, processes, and behaviors of plants and humans can understand how different organisms direct their activity to the same ends.
Among the useful points of comparison are the different ways that both humans and plants sense (see plant perception) their environments, gathering information that, mostly mindlessly, is used to facilitate short- and long-term adaptation.
This information processing takes many proximate forms as both minded and mindless strategies that maximize fitness, that is, support the goals of the biological axiom. So, for example, in plants there is phototropism (bending toward light), gravitropism (root growth in response to gravity), and chemotropism (root growth toward nutrients) that resemble cognitive processing in animals. The similarity lies, not in structures (the root growth, nerves, and brains as different means to same ends), but in the functions, ends, or goals to which the activities of these structures are directed.
Like all other organisms plants (mindlessly) compete for resources, resist predation and disease, adapt to changing short- and long-term environmental conditions. herbivore attacks, and changing conditions. They employ various strategies, like chemical defenses, resource allocation, and communication through chemical signals (allelopathy), to address these challenges. These adaptive responses are mindless ways of problem-solving that, as every biologist knows, can be astoundingly cunning and astute.
Plants communicate using chemical, visual and other signals that convey information to neighboring plants, beneficial organisms like pollinators, and enemies like predators.
Like humans, plants use sensing, adaptation, information processing, problem-solving, and communication as part of their evolutionarily inherited toolbox that mindlessly supports their ultimate, objective, and universal propensity to survive, reproduce, and flourish.
In sum, the cognitive metaphor of “plant intelligence” highlights the remarkable adaptability and responsiveness of plants to their conditions of existence. It underscores the fact that the same universal goals of all organisms are pursued using different configurations of structures, processes, and behaviors. That plants, while lacking a central nervous system and consciousness, exhibit a form of sophisticated information processing and problem-solving that allows them to thrive and persist in diverse ecological niches. This metaphor challenges our traditional notions of intelligence and expands our appreciation for the complexity of the plant kingdom.
It draws attention to the possibility of the notion of ‘intelligence’ being expanded out of the human realm into that of non-human organisms. This would be an acknowledgment of the fact that human mindedness and cognition does not invent mindless biological agency as cognitive metaphor, rather, human agency is a highly evolved form of biological agency.

Agential function
What is the speaker attempting to convey with talk of ‘plant intelligence’? What is the likeness being compared?
The speaker is addressing agency and goal-directedness. While plants and humans have very different structures, these structures have evolved to meet the same preconditions for life. Organisms have individual means of attaining universal ends. It is not uniquely-defining structures that are being compared here, but shared ways of attaining the same ends. We do not understand agency as a biological phenomenon by comparing those characteristics that uniquely define humans with those characteristics that uniquely define plants: we understand agency by examining those shared characteristics that are a consequence of their common ancestry.
Structures & concepts
Just as widely diverse physical structures can have features in common as a result of common ancestry, so too can the biological concepts that relate to them.
We have already seen how the shared and universal characteristics of biological agency are are manifest in many unique physical ways.
This is best understood by example.
Empathy
For this reason – which amounts to a human empathy with biological agency – biology will never rid itself of teleology because this is a teleology that is grounded in the reality of evolutionary connection.
If biological agency, goals, purposes, and values are real then their investigation can be transferred out of the realm of philosophical speculation and into the domain of scientific explanation.
We have yet to scientifically accept that biological agency is not a metaphorical creation of human agency: human agency is a real evolutionary development of biological agency.
What is being compared in this analogical reasoning is the way in which different agents and agential modes attain the same agential goals.
The agential mode is a generalized (non-cognitive) understanding of an agential concept. So, for example, intelligence has been accepted as being related to ‘the agent’s ability to succeed or profit with respect to some goal or objective, and
it depends on how able the agent is to adapt to different objectives or environments‘.
Intelligence, as a biological property, can be expressed as difference (the uniquely minded terms of human agency), or similarity (the universal generalized terms of biological agency). The point here is that when comparing any biological structure, process, or behavior it is possible to consider it in terms of both its similarities and differences.
This is counterintuitive because we assume that if something is unique then there can be no comparison. So, for example, either plants have minds or they do not. But products of evolution have the strange property of simultaneously displaying both similarities and differences. Structures may be uniquely different in some ways while, at the same time, sharing evolutionarily related characteristics. The same applies to agential characteristics.
The objects of comparison in typical cases regarded as cognitive metaphor are not structures but functions. The comparison being drawn, the relata, are not between organs but functional (agential) outcomes. We say a plant ‘wants’ water, not because it has a brain with human desires (structure), but because we recognize that without water it will not survive (agential function).
This simple but unlikely principle of agential function applies to many cognitive characteristics, most notably reason, knowledge, and value (see more detailed discussion), but including memory, learning, choosing, strategies and other cognitive terms that regularly occur in the biological literature for reasons that are now transparent.
Plant intelligence
The discussion so far has concluded that the use of cognitive language for plants is an attempt to capture the reality of non-minded biological agency. There is no language at present to adequately describe the mindless component of biological agency. Without its acknowledgment, the obvious agency of non-minded life takes on the characteristics of the inanimate world.
Possible solutions to this dilemma are discussed in the articles being like-minded and human-talk. Suffice it to say here that the traditional strict distinction between the minded and mindless is, like the notion of consciousness, now being perceived in a more graded way. Non-intuitively and in the absence of a suitable language expressing non-minded agency, it makes sense to extend the meaning of cognitive terms to include non-human organisms or find some scientifically effective way of recognizing mindless agency.
The expression ‘plant intelligence’ may be legitimately used in two senses: in a literary sense as metaphor, and in a biological sense as simile.
Definition
What counts as plant intelligence depends on how we define intelligence (assuming we are not confused about the meaning of ‘plant’).
Plant intelligence, sometimes referred to as plant cognition, is the manifestation, in plants, of the mind-like properties generally referred to as ‘intelligence’. These properties are mind-like because they display the agential goal-directed behavior that we associate with human minded intentions so a good place to start is with an understanding of what is generally understood by ‘human’ intelligence.
That which intelligence tests measure,
These intentions occur more broadly in nature in a mindless way as the universal agential goal-directed behavior that is grounded in the biological axiom.
However, we don’t talk about plant ‘sense’ and plant ‘intelligence’ because we think that plants have human-like sensations, thoughts, feelings, and intentions. The ‘likeness’ we are describing cannot be found by looking at the characteristics that uniquely define plant agency or human agency: instead, we find it in the universally shared characteristics of biological agency (biological axiom).
This connection between plant agency and human agency needs further explanation. The agency of all organisms is evident in flexible behavior that is ultimately directed towards survival, reproduction, and flourishing as organisms demonstrate their autonomy by acting on, and responding to, their conditions of existence. This universally motivated behavior is expressed by each organism through its uniquely evolved structures and processes.
In other words, the systems of communication and information processing found in both humans and plants serve the same universal agential goals, each organism interacting with its conditions of existence in its own unique way.
The ‘likeness’ that exists between human intentions and some plant behavior therefore lies in their real and shared biological agency or functions, not an identity of structures. This is a real evolutionary connection grounded in biological agency, not a metaphorical comparison (see below).
For simplicity, a distinction is made on this website between plant perception – as the various ways in which plants sense their conditions of existence as described in the article on plant sense – and plant intelligence as defined above and discussed in this article.
Biological agency, as goal-directed behavior, is a real phenomenon; it is exhibited by all living organisms, and it operates in a mostly mindless way. For organisms to behave as autonomous agents that act on, and respond to, their conditions of existence (survive, reproduce, and flourish) – they must, of necessity, have an integrated system of communication and information processing that both protects and enhances their autonomy.
Biology faces a dilemma. How can it provide a scientific account of the fact that – while plants do not have brains and minds, and they do not perceive as humans do, they nevertheless interact with their conditions of existence[2] in an agential manner that is not found in the inanimate world. How are we to incorporate agency into plant physiology by inserting ‘life’ into lifeless mechanical explanations of behavior?
The conditions of existence faced by all organisms are broadly similar and evolution has provided many ‘solutions’ to these problems. Highly evolved human minded behavior is just one of the many biological ways of addressing the same agential challenges.
History of the idea
Dating back to ancient history the personification of plants, claims of human-like plant sentience, and the application of anthropomorphic language to plant behavior has been commonplace but, since the Scientific Revolution, dismissed from the mainstream canon of biological science.
The idea gained some traction no doubt from Charles Darwin in the book The Power of Movement in Plants (released 6 Nov. 1880 by publisher John Murray and co-authored by Darwin’s son Francis).[1] Before long about 1500 copies had been sold.[2]
Darwin noted that plant root tips behaved in a simple agential way resembling the brain-initiated activities of some lower animals. He observed that, even in the absence of brains and nerves, plants responded to sensory input.[5] even though plants possess neither brains nor nerves.
‘The course pursued by the radicle in penetrating the ground must be determined by the tip; hence it has acquired such diverse kinds of sensitiveness. It is hardly an exaggeration to say that the tip of the radicle thus endowed, and having the power of directing the movements of the adjoining parts, acts like the brain of one of the lower animals; the brain being seated within the anterior end of the body, receiving impressions from the sense-organs, and directing the several movements.’
The idea of plant intelligence and cognition was dismissed by mainstream science because plants were considered passive and inert – more akin to objects in the inanimate world: they were devoid of agency. Only humans expressed ‘real’ agency.
By the 1960s it had, however, become recognized that plants use many systems of communication – systems of information processing, signaling, and networking etc. – that contribute to their goal-directed behavior. These systems involved chemicals, electrical signals, sound etc. and their investigation became an exciting new and respected field of empirical research. It was a crucial aspect of what is referred to on this PlantsPeoplePlanet website as biological agency. Experimental evidence revealed that plants exhibited modes of plant perception, communication, problem-solving, anticipation, and learning. Clearly, plants were interacting with their conditions of existence in many ways – but how was this to be described in a non-agential way?
The first serious modern-era attempt to describe plant intelligence was published in 2003 by Anthony Trewavas 2003[8] who, joined by other researchers, attempted in 2020 to explain ‘how’ plants are intelligent.[9] Among his co-authors was Monica Gagliano, a widely published plant behavior scientist from the University of New South Wales, Australia.
The term ‘plant neurobiology’ was coined by Stefano Mancuso and František Baluška in their 2006 book titled ‘Signaling in Plants: Sensory Perception and Signal Transduction.’ The authors used the term to draw a parallel between plant signaling and the nervous systems of animals. The term ‘plant neurobiology’ was controversial because it uses the word ‘neurobiology’ to describe processes in plants that are not directly analogous to nervous systems in animals. However, it showed that plants have a complex network of electrical and chemical signals that can transmit and integrate information across different parts of the plant body, and that these signals can modulate plant behaviour and physiology in response to environmental changes – and, that there could be communication between plants.
It was, however, quickly pointed out that plants do not have neurons or synapses, and that the analogy between plant and animal signaling systems is confusing, inappropriate, and scientifically incorrect Any analogies between animal neuroscience and plant biology were best avoided altogether.
A different approach was to look at the situation from a behavioral and ecological perspective by examining the adaptive outcomes of plant behavior rather than the mechanisms involved. Expressions such as ‘plant intelligence’, ‘plant behaviour’ and ‘plant cognition’ were used in this research to denote plant traits resembling decision-making, memory, learning, recognition, awareness, and even consciousness . . . without necessarily requiring a brain or nervous system. Plants were, in effect, cognitive agents interacting with their environment and other organisms.
Plants may lack mobility but they are not passive: they act on, and respond, to their conditions of existence in a flexible and agential way. Jagadis Bose and Lyall Watson, among others, noted that plants have communication systems that respond to and process information from stimuli in a similar manner to animal nervous systems. However, this comparison of humans and plants appeared far-fetched and unscientific and the methods rudimentary.
Discoveries in molecular biology and the advent of advanced imaging techniques in the late 20th century provided new research tools that revealed intricate signaling networks including the operation of chemicals such as hormones that facilitated adjustment to surrounding conditions.
Ecological knowledge, like Suzanne Simard’s work on mycorrhizal networks, draws attention to underground communication systems and resource-sharing as a form of plant cooperation, as outlined in a popular publication in 2022.[6]
There are now extensive studies of the effect of sound, light, chemicals, and many other factors contributing to the study of plant perception and plant behavioral networks can be subjected to modelling by AI and other means.
Biological agency, as goal-directed behavior, is receiving increased recognition in a biology that recognizes the agential adaptive character of both short term behavior and long-term genetic adaptation.
Anthony Trewavas and others at Edinburgh University, called The Edinburgh Molecular Signalling Group, proposed that plants exhibited a kind of distributed intelligence, where local ‘decision-making’ processes contributed to overall flourishing. Trewavas’s work has been particularly influential.[4] He has summarized his thinking in an article Plant Intelligence: An Overview, published in Bioscience in 2016.[3]
A few quotes from this paper provide the flavor of his thought:
‘Intelligent decisions are constantly required to optimize the plant phenotype to a dynamic environment . . . Spontaneity in plant behavior, the ability to count to five, and error correction indicate intention. Volatile organic compounds are used as signals in plant interactions and may be the equivalent of language accounting for self- and alien-recognition. Game theory describes intelligent competitive and cooperative interactions. Profiting from experience requires both learning and memory and is indicated in the priming of herbivory, disease, and abiotic stresses.’
He points out a study in 2007 by that Legg and Hutter[5] with some 70 different definitions of intelligence, summarized as follows:
Intelligence is:
(a) a property that an individual has as it interacts with its environment or environments,
(b) related to the agent’s ability to succeed or profit with respect to some goal or objective, and
(c) depends on how able the agent is to adapt to different objectives or environments. These descriptions of intelligence apply directly to plant behavior and fitness.
His article concludes:
‘Plant behavior is similar to cognition in an analogous sense to that of a human being. A plant continually gathers and updates diverse information about its environment, integrates this with information on its present internal state, and then makes decisions that reconcile its well-being with its environment. Understanding plant behavior and intelligence has become one of the most exciting new and fast-moving frontiers in plant biology.’
A paper by Colaço[1] in 2022 introduces the formal literature on debates about plant cognition. He draws attention to obvious criticisms: that the use of minded words like ‘cognition’ in relation to plants is a ‘non-literal metaphor’ and that it is, therefore, unnecessary since plant behavior can be explained adequately in non-cognitive terms. That anthropomorphism might have heuristic appeal, but it is simply a confusing way of referring to plant information processing.
Colaço proposes that, while plants are ‘not cognitive’, investigating plant cognition is a worthwhile enterprise since it can inform analysis of the concept(s) of cognition and the ‘similarities and differences between the set of phenomena to which these concepts extend’.
This aligns somewhat with the view expressed here on PlantsPeoplePlanet that the concept of cognition serves science most effectively when it is regarded as real across the community of life (what Colaço calls a ‘natural kind’). It is expressed differently in different organisms according to their evolutionarily derived structures, processes, and behaviors and it also, as a consequence of evolution, exists in nature by degree. As a necessary component of all behavior, whether minded or not, cognition is an important ingredient of biological agency.
The challenge remains to clarify what is meant by ‘cognition’ and ‘intelligence’ when used in plant science. Also, to determine the criteria and methods for testing plant cognitive abilities, identifying the evolutionary origins and functions of plant cognition, and exploring the ethical implications of recognizing plants as cognitive beings.
Agency & evolution
Biological agency – as the goal-directed and flexible behavioral propensity to survive, reproduce, and flourish – is a life-defining characteristic since organisms that do not fulfil these criteria cease to exist.
As a life defining characteristic, biological agency was necessarily expressed by the first life, which preceded humans by about 3.5 billion years.
The community of life that evolved out of the first life forms manifest biological agency in a bewildering array of organisms, each species with its own particular combination of structures, process, and behaviors, and each individual way of expressing agential goals through the interaction of these factors and its conditions of existence.
Human agency
Human agency is a highly evolved form of biological agency. That is, human agency arose out of biological agency. In this sense, biological agency is prior to human agency . . . biological agency gave rise to or ‘created’ human agency; human agency did not invent, create, or imagine, biological agency.
The Evolutionary Paradox
Evolution is an expression of a physical continuity that proceeds by modification from common ancestry. Organisms, therefore, share some of their characteristics with other organisms while, at the same time, displaying their own unique characteristics. This is a critical aspect of evolutionary biology that has profound philosophical consequences and therefore warrants a more detailed explanation.
Establishing the evolutionary context of any organism, structure, process, or behavior entails more than a description of its uniquely defining characteristics, it must also include consideration of characteristics that are shared with its evolutionary relatives.
Evolutionary analysis investigates both similarities and differences as it distinguishes between the shared characteristics that are a consequence of common ancestry, and those characteristics that uniquely define the object of investigation.
This is an important general principle of evolutionary biology and, since it has consequences in other fields of knowledge, it is referred to here as the evolutionary paradox. It is a paradox because in an evolutionary context (the comparison of biological objects from an evolutionary perspective) the same object can express both similarity and difference. The fact that similarity and difference seem to imply contradiction does not indicate that one is real and the other imaginary: in evolutionary biology both are real.
The paradox & plants
Both plants and humans as living organisms share the same objective, universal, and ultimate goals of biological agency.
As autonomous biological agents both humans and plants are constantly interacting with their conditions of existence. Humans express this agency in large part (but not entirely) through minded intentions and other uniquely human cognitive characteristics associated with brains and nerves. Plants express the same goals in mindless ways and with a different suite of structures, processes, and behaviors. While these structures, processes, and behaviors are vastly different, they are the outcome of the same evolutionary process, so there is a real evolutionary connection between them.
This is where the evolutionary paradox is crucial.
Humans have unique cognitive capacities that plants do not possess and, in this sense, the likeness between plant intelligence and human intelligence is non-literal, fictional, or metaphorical.
But, as we have seen, plants also share agential properties with humans. This is not the fictitious likeness of metaphor; it is real likeness grounded in a shared evolutionary history that was driven by biological agency.
What for?
Why do we keep using such confusing anthropomorphic language? After all, we can describe what goes on in plants in appropriate plant language without resorting to all these human terms, which might be viewed as both unscientific and childish.
This is a long-standing general problem in biology that is discussed in detail in the articles human-talk and being like-minded.
Briefly, biology has not yet come to terms with biological agency. If the only true and scientifically acknowledged agency in living systems is human minded agency then how are we to understand and explain the goal-directed behavior of non-human organisms?
It is becoming increasingly evident that describing this form of agency in the mechanical non-agential way that we describe inanimate matter is no longer scientifically acceptable. Human agency is just one manifestation of a more generalized biological agency, a fact that only became scientifically apparent post-Darwin.
The use of an expression like ‘plant intelligence’ attempts to capture similarities of agential behavior that are shared by both humans and plants. Here lies the paradox. Given the conventional understanding of intelligence as mind- and brain-dependent, then we must interpret the expression ‘plant intelligence’ as metaphor. But this denies the very characteristics that the expression is attempting to communicate – the real mind-like agency (goal-directed behavior) that they display. Metaphors are fictions, but the shared agency of humans and plants is a real product of evolution: the agency of human subjectivity was generated by this agency. This ambiguity is described on this website as the metaphor fallacy.
The acknowledgment of plant agency acknowledges the evolutionary agential connection between plants and humans. It brings plants closer to humans and further away from goal-less and inanimate mechanical systems.
While plants have neither brains nor nerves, the expression ‘plant intelligence’ is a way of designating plant characteristics with the same agential characteristics as human cognitive characteristics.
Until we have a system of terms that convey the reality of biological agency we will communicate the agency of non-human organisms using the language of human agency.
Evolution
To place an organism, structure, process, or behavior within an evolutionary context it is necessary to describe not only its uniquely defining characteristics but also those characteristics shared with its evolutionary relatives.
Plants do not have minds, but they do have mind-like properties that are an expression of evolutionarily related universal biological agency. While only humans have a conscious capacity for highly developed abstract thought and language, they share with all other organisms the property of biological agency as the capacity to survive, reproduce, and flourish.
The notions of plant intelligence and plant cognition have significant implications for the way we perceive plants and our relationship with them. It challenges the traditional boundary between animals and plants and invites us to reconsider our assumptions and attitudes towards these living beings that share our planet. It also opens up new possibilities for learning from plants and discovering additional plant secrets and potentials.1
Intelligence, perception, cognition
Mental phenomena, and the terms we use to describe them, tend to merge into one-another.
We generally use the word ‘intelligence’ when referring to capacities of learning, reasoning, problem-solving, and adapting. ‘Cognition’ shares these characteristics but tends to be more specifically related to mental processes like perception, memory, attention, and language. Intelligence encompasses broad cognitive skills while cognition refers to specific mental functions that contribute to intelligent behavior. Cognitive scientist Steven Pinker refers to intelligence as ‘the pursuit of goals by inference’ while a more mundane definition is ‘that which intelligence tests measure’.
For our purposes, these two ideas are considered synonymous with a distinction sometimes drawn to aid clarity.
The objective, universal, and ultimate characteristics of biological agency Human agency evolved out of biological agency, its unique properties being highly evolved developments of pre-existing and more generalized agential characteristics.
In order to survive, reproduce, and flourish, all organisms, as biological agents, must have the capacity to acquire, process, store, and use information. This is not a property to be found only in human brains.
To simplify the presentation of ideas The two articles on plant perception (as plant sense) and plant intelligence (plant cognition) therefore examine the precursor conditions are agential parallels to human. Being human it seems appropriate to consider how precursor conditions relate to human agency but a more systematic evolutionary biology approach would probably begin with simple agency, leading gradually into highly evolved human agency.
To simplify the presentation of ideas perception and cognition are treated separately on this website although the two are closely integrated in operation.
Expressed in simple human terms, perception provides the sensory input which cognition then structures, processes, and interprets to provide meaningful experience.
Perception and cognition are related but distinct psychological processes. Perception refers to the initial process of sensing and interpreting sensory information from the environment, including inputs such as visual, auditory, tactile, and other sensory cues. It involves the brain’s ability to organize and make sense of sensory data, forming a representation of the world around us.
Cognition, on the other hand, encompasses a broader range of mental processes beyond sensory input. It involves higher-level mental activities such as thinking, reasoning, problem-solving, memory, language use, and decision-making. Cognition goes beyond the raw sensory input to involve the manipulation, interpretation, and integration of information. It draws on memory, previous experiences, and learned knowledge to process and understand the world, make judgments, and engage in complex mental tasks.
In summary, perception is primarily concerned with the initial processing of sensory information, while cognition involves more advanced mental activities that utilize and manipulate information beyond sensory input.
Perception
In humans, perception processes the raw information of sight, hearing, touch, taste, and smell as brain input that recognizes patterns. Perception occurs immediately and intuitively and is modular, in the way that individual senses provide information about specific aspects of the world. It can be deceived.
Intelligence & Cognition
Human cognition coordinates mental processes into a form that makes existence meaningful, that helps us obtain knowledge and understanding. We associate cognition with thinking, knowing, remembering (memory), valuing, and reasoning as a process of problem-solving – activities we associate with language, imagination, perception, and planning, learning.
Thought as segregation-categorization, focus, classification, and ranking.
For the purposes of exposition in this article, plant sense and plant perception are treated as synonymous, as are plant intelligence and plant cognition.
Cognition involves the integration of perceptual and other information into meaningful experience. In humans, cognition entails thinking, reasoning, problem-solving, decision-making, memory, and language comprehension. This, in turn, requires the formation of concepts, categories, and mental models. Cognition involves anticipation (foresight) with prior knowledge, expectations, and context all influencing the interpretation and processing of information. It is not immediate, like perception, but may involve time for planning, reflection, and problem-solving. Human cognition incorporates abstract thinking, symbolic representation, and the ability to reason about concepts that may not have direct sensory counterparts. It can be self-aware, and self-reflective (thinking about thinking) it includes imagination, creativity, and the generation of novel ideas and concepts that are independent of sensory input.
They are mental processes and abilities involved in acquiring, processing, storing, and using information. It encompasses a wide range of Cognition is generally understood as comprising uniquely mental processes performed in brains. It includes the use of perception, attention, memory, reasoning, problem-solving, language comprehension, and decision-making.
Cognition is part of the process of interaction between an organism and its conditions of existence (which is more than just its environment). Associated with cognition there is a processing of sensory inputs, learning from experience, and the integrated processing of all these factors.
In humans, cognition engages brain functions that include the operation of neural networks, and the initiation of behavior, learning, and adaptation to circumstance.
Possible – PlantsPeoplePlanet explores the fascinating concept of plant intelligence, delving into the remarkable abilities exhibited by flora in perceiving and processing information. Through an exploration of plant intelligence, this website aims to shed light on the intricate world of plant intelligence, revealing the hidden depths within the vegetal realm. From their capacity to respond to environmental stimuli to their ability to communicate and make decisions, plants’ cognitive abilities showcase the complexity and interconnectedness of all life on our planet. Embark on a journey of discovery as we unravel the mysteries of plant intelligence, unlocking a deeper understanding of the awe-inspiring intelligence that exists within our green companions.
Plant intelligence & cognition
Plant intelligence and cognition, as defined in this article, is not related to human agency by employing similar structures, like nerves and brains. While plants are, indeed, evolutionarily related to humans, the comparison that is being made here – the elements of ‘likeness’ as factors being compared – are not physical structures, but modes of agency.
Both plants and humans demonstrate ways of adjusting to their circumstances of existence that are constrained by their unique combinations of structures, processes, and behaviors.
from their . Instead understood in this article Plant cognition is simply the expression of evolutionarily related – through the mind-like agential properties of all living organisms – characteristics such as the capacity to learn and remember (see Wikipedia).
It may be pointed out that to speak of plant ‘learning’ and ‘memory’ is simply misrepresentation, because such characteristics are inextricably associated with minds. However, there is no doubt that plants exhibit characteristics that are like learning and memory. These characteristics are not present in the inanimate world or dead bodies: they are part of the manifestation of biological agency.
Motility
The evolution of neural systems and central nervous systems may be related to the motility that allows organisms to face the challenges of diverse environments.
Plants, despite their inability to move, have evolved an array of remarkable adaptations that enable them to survive and thrive in diverse environments. Their extensive root systems anchor them firmly in place and facilitate the absorption of water and nutrients from the soil. Some plants develop deep taproots to access water deep underground, while others spread fibrous roots across a wide area to maximize nutrient uptake.
Through phototropism, plants grow toward light sources, optimizing their exposure to sunlight essential for photosynthesis. Complementing this, gravitropism directs roots downward and shoots upward, ensuring proper orientation, while thigmotropism allows climbing plants to respond to touch by wrapping around structures for support.
To defend against herbivores, plants employ both chemical and physical strategies. Many produce toxic compounds like alkaloids, tannins, and essential oils that deter animals. Physical defenses such as thorns, spines, and tough leaves further protect them from grazing. Some even engage in allelopathy, releasing chemicals that inhibit the growth of neighboring plants, reducing competition for resources.
Symbiotic relationships enhance survival prospects. Legumes form partnerships with nitrogen-fixing bacteria to obtain essential nutrients, while mycorrhizal associations with fungi extend root systems, improving water and nutrient uptake. These relationships are crucial in nutrient-poor soils and create complex underground networks facilitating inter-plant communication.
Since they cannot move to spread their seeds, plants have evolved diverse seed dispersal mechanisms—wind, water, and animals. Specialized structures like wings or hooks aid in their movement. Additionally, many plants reproduce asexually through runners, tubers, and cuttings, rapidly colonizing areas without relying on seeds.
Plants exhibit significant phenotypic plasticity, adjusting their growth and development in response to environmental conditions. Their totipotent cells enable regeneration and healing, allowing them to recover from damage and adapt their form as needed.
To cope with unfavorable conditions like extreme cold or drought, many plants enter a state of dormancy, conserving resources until conditions improve. Others have adapted to grow and reproduce rapidly, completing their life cycle during brief periods of favorable conditions—a strategy common in annual plants.
Additional adaptations include:
Volatile Organic Compounds (VOCs): Emitting chemicals to communicate distress or attract predators of their herbivores.
Structural Specializations: Succulents store water in fleshy tissues; epiphytes grow on other plants to access light; carnivorous plants capture insects to supplement nutrients.
Alternative Photosynthetic Pathways: CAM and C4 photosynthesis allow efficient water use and carbon fixation in challenging environments.
Defense Through Mimicry and Camouflage: Some plants mimic the appearance of less palatable species or display patterns that deter herbivores.
Water and Nutrient Conservation: Reducing leaf size or shedding leaves during dry seasons minimizes water loss; evergreens have needle-like leaves with waxy coatings.
Through this intricate combination of structural, chemical, and behavioral adaptations, plants overcome the challenges of immobility. They engage actively with their environment, forming alliances, defending against threats, and optimizing resource use. These strategies not only ensure their survival but also contribute to the balance and vitality of ecosystems worldwide.
Commentary
As scientific knowledge has progressed and evolutionary theory has become more embedded in biological thinking there has been a re-evaluation of the philosophical implications of the interconnectedness of all life forms. Biological science is now deeply grounded in a post-Darwinian evolutionary biology that recognizes physical gradations and continuities but fails to recognize the physical and agential antecedents to human mental phenomena and the way that cognitive behavior is more closely integrated with other life forms than we previously thought. Human agency is simply a highly evolved and minded form of a more generalized and mindless biological agency.
Biological science has yet to exorcise philosophical demons by naturalizing the relationship between mindless biological agency and minded human agency.
The notion of plant intelligence can only gain traction because it draws attention to a similarity or likeness that captures our attention. This likeness does not lie in identical physical structures, instead it is drawing our attention to the fact that both humans and plants are addressing the same universal problems of existence – the necessity to survive, reproduce and flourish. The likeness is in the way that different structures can serve the same functions, they are addressing the same ends. The real ‘likeness’ being compared here is not about structures, but functions. If we wish to compare the agencies of two organisms we can do so by comparing either the unique physical structures that express that agency or the way that these unique structures achieve the same agential outcomes.
Plants exhibit a range of responses to their environment, from sophisticated chemical signaling to communication through root networks. Some researchers posit that these behaviors might constitute a form of rudimentary consciousness, although distinct from that of animals. This viewpoint suggests that the definition of consciousness needs to be broadened to encompass a spectrum of cognitive experiences across different life forms.
Science cannot change the meaning of words but within its discipline it can redefine their meaning according to the latest scientific evidence.
Agency has two key components: abstract goals that are expressed as a behavioral disposition, and the physical structures and processes that manifest these goals.
Media Gallery
First published on the internet under the heading ‘Plant cognition’ in August 2023
. . . 18 August 2023 – substantial revision
. . . 25 August 2023 – first completion of logical flow from metaphor fallacy to agential function
. . . 31 August 2023 – refining ideas in preparation for removal of ‘Work in Progress’ symbol
Biological Revolution
Theoretical biology is currently experiencing a paradigm shift in its foundational ideas as the concepts of agency and cognition are extended beyond the human (sentient) domain to non-human organisms.
Biological agency is evident in the universal capacity of organisms to act on and respond to their conditions of existence in a unified, goal-directed, and flexible way - as the objective and ultimate capacity to survive, reproduce, adapt, and evolve (the biological axiom).
The observable behavior that establishes biological agency is generated by functionally integrated internal processing. This is a universal form of biological cognition as understood in a broad sense as the means by which organisms access, store, retrieve, process, prioritize, and communicate information as a prelude to goal-directed activity. These same universal characteristics are exhibited by functionally equivalent structures, processes, and behaviors of all organisms with human cognition one highly evolved form.
Human agency and human cognition are highly evolved and species-specific examples of universal biological agency and universal biological cognition. Our anthropocentrism and awareness of our own mental states have led us to describe functionally equivalent adaptations of other organisms using the language of human cognition and intentional psychology. This misuse of language, which also implies evolutionary similarity, is therefore treated as cognitive metaphor. This ignores the fact that functionally equivalent adaptations (expressed in evolutionarily graded form) need not necessarily express direct evolutionary connection and, more importantly, they currently lack an appropriate functionally descriptive terminology. Functional equivalence is a genuine feature of biological systems. Human physical mental faculties (many uniquely human), such as sentience, subjectivity, experience, perception, reason, value, knowledge, memory, learning, communication, etc. have functional equivalents in other organisms that do not, and need not, demonstrate physically direct evolutionary connection. We have a well-established biological language for structural comparison, but no equivalent language for functional comparison.
These philosophical changes are part of the framework of the Extended Evolutionary Synthesis (EES) which expands on traditional evolutionary theory by incorporating new insights from developmental biology, epigenetics, and ecology, notably the acknowledgment of organisms as active participants in their own evolution, shaping their own developmental trajectories and those of their descendants.
This re-evaluation of the human relationship to other species represents a significant expansion of human knowledge. It opens new research fields, challenges the foundations of theoretical biology, and has ethical implications for the way we interact with other living beings.
Biological objects
The miracle of life is traditionally presented to student biologists through the categories and concepts of the hierarchy of biological organization. This presents a view of science that is grounded in ancient and ambiguous ideas about the structure of reality. Building biological understanding around the agency of organisms (their parts and communities) and the categories of structure, process, and behavior offers a more comprehensive, simple, and dynamic conceptual framework for contemporary biological investigation that is grounded in current biological research. It balances ontological rigor with pragmatic flexibility, which is important for both educational and research purposes by providing categories that are both philosophically sound and practically useful.
Structures: the tangible physical building blocks of biology, ranging from sub-organismal entities like molecules, genes, cells, tissues, and organs, to supra-organismal entities such as colonies, populations, ecosystems, and the biosphere.
Processes: the biochemical and physiological activities that sustain life, such as photosynthesis, homeostasis, growth, metabolism, and reproduction. Also the long-term changes addressed by evolutionary biology. These dynamic activities are often obscured when focusing solely on structural descriptions.
Behaviors: the actions and responses of organisms within their environment. These can be both minded and mindless, in both organisms and their parts, and are often goal-directed, even in a minimal sense, by having specific functions.
This tripartite classification reflects the historical development of biological investigation - as an inventory of static structures (histology, anatomy, morphology, taxonomy) to dynamic processes and functions (physiology, developmental biology, ecology, evolutionary biology, systems biology), and then behaviors and agency (ecology, ethology, psychology, cognition). It emphasizes that structures support processes and processes drive behaviors in dynamic interactions and responses, capturing the complexity and adaptability of life in a comprehensive way.
This progression of investigative categories shows how biology has increasingly integrated the concepts of time, change, function, and agency through the interplay of physical structures, functional processes, and adaptive behaviors. It is a tool that reflects the character of contemporary biology in a categorization that helps students progress logically from understanding physical makeup to exploring interactions in the real world, which underscores the educational value of the approach.
Agency & Cognition
Living organisms are canonical biological agents that demonstrate their autonomy as a unity of purpose - the behavioral propensity to survive, reproduce, adapt, and evolve (biological axiom). Biological agency is therefore most apparent in their flexible and adaptive goal-directed behavior as they respond to their changing conditions. The diversity of biological structures, processes, and behaviors we see in the community of life represent the range of evolutionary adaptations that have arisen in response to these universal biological conditions.
Internal processes drive observable agential behavior and all organisms, if they are to adapt, must have the capacity, no matter how crude, to both represent and interpret their conditions of existence. Human cognition is conventionally associated with the coordinating activities of the brain and nervous system, but this mental form of cognition is just one manifestation of the many functionally equivalent internal processing systems that occur in all organisms. Human cognition is therefore a uniquely human specialized evolutionary response to the conditions of the biological axiom: it has functional equivalents in all other organisms and is collectively referred to as biological cognition.
Thus, biological agency is identified and explained primarily through observed external behavior while biological cognition is the less accessible functionally integrated internal processing that generates this behavior. Human agency and cognition are specialized, evolved responses to these existential conditions, expressed as biological agency and biological cognition.
The use of human cognitive terms like ‘experience,’ ‘subjectivity,’ ‘perception,’ ‘intelligence,’ ‘choices,’ ‘decisions,’ ‘learning,’ and ‘memory’ traditionally applies uniquely to humans. When used for non-human organisms, these terms denote functional equivalence, not direct evolutionary connection.
The challenge for theoretical biology is to find a descriptive language that distinguishes between uniquely human cognition and functionally equivalent biological cognition without resorting to cognitive metaphor or undermining functional equivalence.
Functional Equivalence
Biological objects may be compared from at least two evolutionary perspectives – their physical ancestry, and functional equivalence. So, for example, likening the behavior of humans and plants by talking about both plant cognition and human cognition does not necessarily mean that plant experiences are the same as human experiences. This is not an equivalence of evolutionary structures, processes, behaviors, and experiences (homologs) but an equivalence of functions (analogs).
Physical functional equivalence, such as the wings of birds and butterflies, can be empirically validated. However, psychological equivalence is more contentious as it relies on interpretive frameworks influenced by our understanding of consciousness and cognition. So, for example, saying a plant ‘wants’ water seems blatant cognitive metaphor.
Assuming human agency and human cognition are highly evolved forms of more general biological traits, functional equivalence becomes more scientifically meaningful since it is grounded in empirically verifiable traits that conform to the biological axiom (to survive, reproduce, adapt, and evolve). When we say a plant ‘wants’ water, we acknowledge its observable biological behavior in response to water stress. This shifts the perspective from metaphorical fiction to functional equivalence grounded in empirical reality, with metaphor serving as a heuristic tool that resonates with human understanding.
Functional equivalence is the real, observable phenomenon, while metaphor is the figurative language used to describe and relate to it.
Using human psychological terms for non-human organisms infers functional, not physical, equivalence. It does not suggest a meeting of minds but a comparison of strategies used to address the same selection pressures - an equivalence of ultimate biological goals. However, it does create a problem for the semantics of cognitive language (see human-talk).

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