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Perception: More than Meets the Eye

Perception and action: Why water tastes good but hydrogen-peroxide doesn't.

Unlike what one may only desire to do, what one actually does is significant because it is the cognitive product that natural selection (part of the process of evolution) operates upon directly. From an evolutionary point of view, what one does is more important than what one feels, intuits, prefers, or represents mentally. ('Mental representation' is a fancy term for conscious or unconscious ideas/knowledge; see definition of 'mental representation' below.) Much of the history of psychology has concerned itself with the nature in which knowledge is represented in the mind. For example, some theories propose that the representation (idea) of a flower is similar to the image one experiences when looking at a flower. As in the definition below, these theories propose that the representation is in some way 'isomorphic' (similar in shape or form) to the thing it represents, as in the case of an internalized 'cognitive map' of one's house.

In contrast, an evolutionary-based (and non-traditional) perspective on the nature of perception begins with the assumption that most mental phenomena must be primarily concerned with how the organism should behave at that moment in time. (This was the 'functionalist' approached adopted by William James and others.) From this point of view, and as beautifully explained in Jeffrey Gray's Consciousness: Creeping Up on the Hard Problem, the nature of the isomorphism to the world remains unclear with respect to many 'representational' processes. What of the outside world does a 'mood' represent? What does the feeling of holding one's breath represent? What does the pungent flavor of hydrogen peroxide represent? This nasty chemical differs molecularly from water only by the addition of a single oxygen atom, but few would perceive it as 'water with a little too much oxygen.' Instead, the toxic chemical is perceived (or 'represented') as something that 'tastes bad' and should be violently expelled from the body.

This may lead one to hypothesize that the representation of hydrogen peroxide is isomorphic with respect to how one should respond to the stimulus, but this is not in line with traditional views of what a mental representation is. It is, however, consistent with an evolutionary-based view in which the guidance of action constrains the properties of mental processes and subjective states. Similarly, in the real (physical) world out there, the color blue and red are just the same thing (electromagnetic frequencies) occurring at different speeds, but no one perceives the color red as a slower version of the color blue. Rather, color perception is intimately associated to action (and not the way the world is): It evolved for selecting fruits and detecting camouflaged prey.

Some representations in vision (e.g., a spatial layout) do seem isomorphic to what is out there in the real world. In such cases, it just so happens that representing space as accurately as possible does lead to the most adaptive response. But representing how things are is not the primary goal of the brain. (Moreover, vision is often far from accurate when representing the world out there. For an amazing and thorough set of optical illusions, click here.)

Thus, 'representational accuracy' is secondary to the adaptive guidance of a response. In this way, evolution has no qualms about Plato's 'noble lie'--that a lie is noble if it leads to a good outcome--provided that such lie (e.g., that hydrogen peroxide has little in common with water) increases evolutionary fitness.

Definition of Mental Representation: The official definition of mental representations is: "a system of symbols isomorphic to some aspect of the environment, used to make behavior-generating decisions that anticipate events and relations in that environment...[and, cognitive] psychology is the study of mental representations" (Gallistel, 2001, p. 9691).

Recommended Further Reading:

Morsella, E., & Bargh, J. A. (in press). Unconscious action tendencies: Sources of 'un-integrated' action. In J. Decety and J. Cacioppo (Eds.), Oxford handbook of social neuroscience. New York: Oxford University Press.

To learn more about Ezequiel Morsella's research and books, please visit his lab's website, the Action and Consciousness Lab.

References cited:

Gallistel, C. R. (2001). Mental representations, psychology of. In N.J. Smelser and P.B.Baltes (Eds.), International Encyclopedia of the social and behavioural sciences (pp. 9691-9695). New York: Elsevier.

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