Embodiment, Psychology, and Neuroscience

How can an embodied perspective help us think about the relation between mechanisms, such as those studied in neuroscience, and the questions psychology asks about perception, action, knowing, and meaning? The issue is whether a mechanistic account and a psychological account necessarily answer the same question, not whether mechanisms are important. One answer comes from a particular flavor of enactivism as put forward by Humberto Maturana and Francisco Varela. Their ideas can help with a wider understanding of what embodiment means and how it can guide our explorations of brain, body, and mind.

Modern science inherited an enormously productive mechanistic way of explaining bodies. Descartes was an important figure in that shift: he sought to explain many animal and bodily functions through material mechanisms while treating mind as a distinct thinking substance (Hatfield, 2024). The mechanistic program was scientifically generative, but it also helped make questions about meaning, perspective, and subjectivity look as though they belonged somewhere other than the organized activity of the animal itself. Enactivism can be read as one attempt to bring those questions back into a naturalistic account of living systems without giving up mechanistic explanation or restoring an immaterial mind.

In his work on color vision in the 1960s, Maturana initially expected to relate patterns of retinal activity to the spectral composition of light. That relation proved elusive. In work with Gabriela Uribe and Sammy Frenk, he instead explored how retinal activity related to chromatic distinctions that were not reducible to spectral composition (Maturana et al., 1968). Very different patterns of light can be experienced as the same color. This became important for Maturana because it unsettled a simple picture in which the visual world is encoded at the sensory surface and then reconstructed inside the brain. What we call color depends on the organization and activity of the nervous system, not on wavelength alone (Maturana, 2002).

Some of Maturana’s earlier work with Jerome Lettvin, Warren McCulloch, and Walter Pitts examined the frog retina (Lettvin et al., 1959). Recording from single fibers in the optic nerve, they found several classes that responded selectively to different local patterns of change in illumination, including moving edges and small moving dark objects. Rather than relaying a point-by-point image to the brain, the retina’s circuitry was already transforming patterns of light into patterns of neural activity. The 1959 paper itself used the language of information, but Maturana later became increasingly critical of treating sensory activity as the transmission of information about an independently specified world (Maturana, 2002).

The frog example later became useful to Maturana for a broader reason. From the standpoint of an observer, the frog sees and catches a fly. But “fly” is not something carried into the nervous system as an instruction for what to do. Changes in illumination perturb a nervous system whose own structure determines what changes can follow. Maturana later developed the idea of structural coupling to describe how an organism and its medium become fitted to one another through a history of recurrent interaction (Maturana, 1978).

The medium has a structure too, and the frog’s activity in turn changes what happens around it. Across recurrent interactions, organism and medium can undergo coordinated structural change. This is a historical relation, but at any particular moment the frog operates through its present structure.

The same point changes how we think about a stimulus. A change in illumination can certainly affect the frog, and a psychologist can call that change a stimulus. The problem comes when the stimulus is treated as though it already contains its psychological meaning or specifies the response that should follow. In Maturana’s terms, the environmental change perturbs the organism. What happens next depends on the structure of the living system and the range of changes that structure makes possible.

Some perturbations are compatible with the continued organization of the living system and some are not. Structural plasticity allows the organism to change while continuing to live. Other perturbations can exceed what its present structure can withstand, resulting in damage or death.

The structure of the organism sets the range of changes it can undergo. Environmental events can trigger changes within that range, but they do not generate the range itself or instruct the organism which response to make. This is the sense in which Maturana describes living systems as structure-determined (Maturana, 1978).

A similar point applies to evolution and development. Natural selection does not generate the forms on which it acts. Development helps generate and organize the variation that becomes available for selection. In both cases, the question is not only what selects among possibilities, but where those possibilities come from in the first place.

This way of thinking cuts across the stimulus-response language that was prominent in much twentieth-century psychology, including behaviorism. Behaviorists differed greatly in what they thought an explanation of behavior required, so it would be too simple to say that behaviorism ignored the organism. But many behaviorist analyses deliberately concentrated on relations between environmental events and behavior rather than on the organism’s internal organization. Maturana pushes the explanatory question in a different direction. A stimulus can be identified and manipulated by an experimenter, but its effect is not specified by the stimulus alone.

The visual studies also give us an example of a present-time mechanism. We can ask how retinal and neural processes operate now to produce a pattern of conduct without answering the different question of how that organization came to exist. Maturana later made this distinction explicit. As he wrote in Biology of Language, “History is necessary to explain how a given system or phenomenon came to be, but it does not participate in the explanation of the operation of the system or phenomenon in the present” (Maturana, 1978, p. 39). This does not make structural coupling ahistorical. Recurrent interactions can leave lasting changes in both organism and medium. The point is that the history is embodied in the structure that exists now; it is not an additional causal ingredient operating alongside present processes.

The Cognitive Domain

Maturana called the range of interactions in which a living system can act in ways relevant to maintaining itself its cognitive domain (Maturana, 1970/1980a). In his early formulation, living and cognizing are inseparable: a living system continues to exist through effective activity in a medium, and the possibilities for that activity depend on its organization and structure. The cognitive domain is not an internal thing the organism contains but a domain of possible and actual interactions through which its living is realized. We, as observers, can then describe conduct in that domain using words such as perceiving, learning, knowing, goals, and intentions.

This is not the same as a mechanistic description of what is happening inside the organism. Maturana was insistent about keeping these levels apart. We can describe the present operation of a nervous system and the structural changes triggered within it, and we can describe the conduct of the organism as seeing, learning, knowing, or acting effectively. Those descriptions concern the same living system, but terms that are useful for describing conduct should not automatically be turned into mechanisms inside the nervous system.

An observer does not invent the organism’s activity. The organism really does act, and its conduct can succeed or fail in relation to the continuation of its way of life. But descriptions such as perception, knowledge, error, or intelligence introduce relations that are distinguished by an observer. Maturana’s framework asks us not to confuse those relational descriptions with the operational processes through which the conduct is produced.

A neuroscientific account can tell us about the processes through which a particular pattern of conduct is produced. A psychological description may concern what the organism is doing: perceiving something, learning a task, remembering a person, acting intentionally. One description does not become the other simply by changing vocabulary. If we want to connect them, we need to show how the organization and activity of the nervous system generate the conduct that the psychological description picks out.

Maturana wanted us to examine the assumptions we bring to those terms. In his broad formulation from the 1970 report Biology of Cognition:

A cognitive system is a system whose organization defines a domain of interactions in which it can act with relevance to the maintenance of itself, and the process of cognition is the actual (inductive) acting or behaving in this domain. (Maturana, 1970/1980a, p. 13)

We do not usually think about cognition as behaving, but Maturana and Varela later compressed the point into the phrase “all doing is knowing, and all knowing is doing” (Maturana & Varela, 1987, p. 26). Their point was that knowing is not first the possession of an internal representation that is then used to guide action; we describe an organism as knowing when its conduct is effective or adequate within a particular domain of interactions. Intelligence can be understood in the same way. Rather than treating intelligence simply as a capacity stored inside an individual, we can ask how intelligent activity is manifested in what the organism can actually do within its cognitive domain.

The Consensual Domain

Maturana carries the same problem into language. We can ask how an organism operates as a structure-determined living system, and we can describe its conduct as effective action within a cognitive domain. When humans describe conduct in terms of objects, goals, intentions, learning, or knowing, however, those distinctions are made in language. That takes us beyond the activity of an isolated observer and into Maturana’s account of the consensual domain (Maturana, 1978).

Part of this idea is obvious: when we talk with someone about something, we use words as part of a shared way of communicating. The subtler point is that, for Maturana, a consensual domain does not begin with people explicitly agreeing on the meanings of words. It develops through recurrent interaction between organisms whose conduct becomes coordinated over time. One person’s action changes the circumstances for the other, whose response in turn changes the circumstances again. Through a history of such reciprocal interactions, patterns of coordinated conduct can develop. When coordination itself becomes something that participants recursively coordinate, a linguistic domain becomes possible. Language, on this account, is not fundamentally the transfer of information from one mind to another but an ongoing coordination of conduct between participants with a history of interaction (Maturana, 1978).

For Maturana, whatever we distinguish as an object is distinguished by an observer with a particular structure and history. This does not mean that anything goes or that there are no stable regularities in the world. As humans, we can collectively investigate a shared physical world, but we do not do so from outside our own embodiment and language. In Maturana’s terms, when we speak about things we are making operational distinctions within a consensual domain rather than simply copying an observer-independent world into our heads. This is one reason embodiment complicates the idea of completely objective access without requiring us to abandon science or a shared world.

For Maturana, an observer is not a detached spectator standing outside the world being described. Human observing depends on language, and language depends on histories of coordinated interaction with other people. Maturana’s way of putting this was that everything said is said by an observer to another observer, who may be yourself (Maturana, 1978). The distinctions we make when we talk about learning, knowing, goals, objects, or explanations therefore arise within social practices of description. This does not mean that organisms or events are invented by observers. It means that the categories through which we describe them have their own history in human interaction.

Enactivism is sometimes read as promoting solipsism, the idea that we can only understand our own individual world and are stuck in it. As Maturana wrote in Biology of Cognition:

The linguistic domain as a domain of orienting behavior requires at least two interacting organisms with comparable domains of interactions, so that a cooperative system of consensual interactions may be developed in which the emerging conduct of the two organisms is relevant for both. (Maturana, 1970/1980a, p. 41)

In the introduction to Autopoiesis and Cognition, he put the point more briefly: “The central feature of human existence is its occurrence in a linguistic cognitive domain. This domain is constitutively social” (Maturana, 1980b, p. xxiv).

So Maturana’s view does not lead to solipsism: He does not adopt the position that our discourse can deal ultimately only with our own subjective thoughts and feelings. By virtue of being a discourse, it lies in a consensual domain, which is a domain that exists for a social community. So our access to reality is not observer-free, but neither is it merely individual. As Maturana noted, just talking about solipsism requires us to have a language that is a consensual domain of interactions in a subject-dependent cognitive domain, which negates the idea of solipsism (Maturana, 1978).

References

Lettvin, J. Y., Maturana, H. R., McCulloch, W. S., & Pitts, W. H. (1959). What the frog’s eye tells the frog’s brain. Proceedings of the IRE, 47(11), 1940–1951. https://doi.org/10.1109/JRPROC.1959.287207

Maturana, H. R., Uribe, G., & Frenk, S. (1968). A biological theory of relativistic colour coding in the primate retina. Archivos de Biología y Medicina Experimentales, 1, 1–30.

Maturana, H. R. (1980a). Biology of cognition. In H. R. Maturana & F. J. Varela, Autopoiesis and cognition: The realization of the living (pp. 5–58). D. Reidel. (Original work published 1970)

Maturana, H. R. (1980b). Introduction. In H. R. Maturana & F. J. Varela, Autopoiesis and cognition: The realization of the living (pp. xi–xxx). D. Reidel.

Maturana, H. R. (2002). Autopoiesis, structural coupling and cognition: A history of these and other notions in the biology of cognition. Cybernetics & Human Knowing, 9(3–4), 5–34.

Maturana, H. R. (1978). Biology of language: The epistemology of reality. In G. A. Miller & E. Lenneberg (Eds.), Psychology and biology of language and thought: Essays in honor of Eric Lenneberg (pp. 27–63). Academic Press.

Maturana, H. R., & Varela, F. J. (1987). The tree of knowledge: The biological roots of human understanding (R. Paolucci, Trans.). Shambhala.

Hatfield, G. (2024). René Descartes. In E. N. Zalta & U. Nodelman (Eds.), The Stanford Encyclopedia of Philosophy (Summer 2024 ed.). Metaphysics Research Lab, Stanford University. https://plato.stanford.edu/archives/sum2024/entries/descartes/