As a constraint on cognition, the body shapes the nature of cognitive activity and the content of the representations processed. Consider color perception, sound localization, categorization, and spatial metaphor. Concepts and experiences of colors, for example, reflect the properties of the retinal cells and the features of the visual apparatus; sound detection owes its peculiarity to the distance between the ears; and spatial metaphors, whose locus is not language but the way we conceptualize the body, heavily draw on embodied experiences.
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Traditional views in philosophy of mind and cognitive science depict the mind as an information processor, one whose connections with the body and the world are of little theoretical importance.
An illustration of this idea comes from the joint work of George Lakoff and Mark Johnson. Beginning in their Metaphors We Live By, Lakoff and Johnson argued that many central cognitive processes, such as those concerning space and time, are both expressed and influenced by metaphors, and that many metaphors reflect bodily features.
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Lakoff and Johnson are the authors of an outstanding and accessible introduction to Conceptual Metaphor titled Metaphors We Live By. It belongs on everyone's Book List.
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Consider a well-known metaphor that they discuss: that of Love as a kind of journey. Here the source domain (journey) is informed by our bodily physicality, and information about the body (such as its capacity for locomotion) shapes the way in which love is understood and conceptualized. Metaphors, hence, are not merely useful for embellishing communication, but reflect the embodied experience that we have as creatures that move through the world in particular ways.
Spatial concepts provide perhaps a clearer example: long and flat creatures would not be capable, as we are, of conceiving the world in terms on ‘front’, ‘back’, ‘up’, and down’. These concepts arise and are articulated thanks both to the particular body we have and the specific ways it navigates in and through space. Although in these examples the physicality of the body does not directly contribute to mental processing, the construction of metaphors shows nonetheless that (1) abstract domains are grounded in more concrete ones; (2) the grounding aspect of the body acts as a Scaffold for articulating thoughts that otherwise would be difficult to communicate; and (3) information about the body is included in the representations that constitute cognition.
Further examples of the body functioning as a constraint on cognition come from findings in behavioral psychology. Our judgments about the usability of tools, about the physical properties of stairs, and about the graspability of objects indeed incorporate anticipated embodied interactions, and are affected both by our bodily features and the motor skills that allow us to cope with those objects and tools.51–53
Another example exemplifying the role of the body as a constraint on cognition comes from Lawrence Barsalou’s perceptual symbols theory.8,54,55 This theory rests on the assumption that human cognition does not consist of amodal representations that bear arbitrary relations to their referents in the world, but rather of representations whose activation patterns include information from various sensory modalities. For example, the symbolic structure that represents an object in its absence, say, during a memory task, depends upon the same neural system that is recruited when the object is actually perceived or acted upon. Thus, not only does cognitive processing essentially reactivate sensorimotor areas in the activity of remembering, but memory itself may be built up out of sensorimotor patterns and thus be modal rather than purely symbolic. On such a view, besides reflecting the nature of embodied interactions, multimodal representations stored in memory assist, control, and facilitate perceptual processing, reasoning, and situated actions.
The body’s constraining effects on cognition can be also seen in relation to language. Sentence comprehension and construal of meaning are achieved through embodied responses and require knowing both the affordances offered by an object and whether they match our sensorimotor capabilities.56–59 Judging the meaning of a sentence is faster and more accurate, for example, if the text meaning is compatible with the body’s biomechanical features.
We should expect, therefore, that differently embodied agents will diverge in their conceptualization of identical situations and that understanding will vary if intelligent systems varied physically. Having a different sort of body thus facilitates a different kind of cognitive processing.