This is an addition to an earlier posting regarding the evolution of cognition and the role of sensorimotor activity and the function of something like ‘action representations’.
A useful distinction to begin to draw here may be that between ‘sensation’ and ‘perception’. I would like to offer that the first of these terms, sensation, refers to the operation of the sensorimotor system in relation to the environment, whereas the second term, perception, is a higher order process. For example; there is a part of the sensorimotor system associated with ‘seeing’ which consists of the eyes and parts of the visual cortex, and also the motor mechanisms which focus the eye, saccade the eyeball in its socket, adjust the dilation of the pupil according to light levels (and the desirability of the object looked at), etc. Together this combination of sensory and motor activity produce the sensation of seeing. This is not the same as perception as I want to use the term however. In order for the results of this sensational seeing to be perceived there needs to be a further operation in which this sensorimotor activity is held as a representation and then made available to other, perhaps specially evolved, cognitive processes. It is this secondary or higher order processing of sensation and action that constitutes perception. To paraphrase Antonio Damasio (2000), sensation is what happens, perception is the feeling of what happens.
Nicholas Humphrey presents an interesting narrative description of this distinction in his essay ‘The Privatization of Sensation’ (2000). He suggests that a simple organism, perhaps something like an amoeba, having only the simplest form of sensorimotor engagement with the world, is capable of sensation but not perception. Such an organism, in the presence of a chemical salt would, he claims, react to that chemical according to the physiological inevitabilities of its embodiment. The composition of its cell walls and its own internal chemistry would be affected by the saltiness of its environment and this affect would express itself in, for example, a characteristic wriggling. Alternatively, if light of a particular wavelength, say a wavelength that would be visible to us as ‘red’, were to fall across this creature another, very different, set of physiological changes would be initiated, perhaps noticeable as a different but equally characteristic wriggling. Humphreys suggests that it would not be irrational to think of the first of these ameobic behaviours as ‘wriggling saltily’ and the second as ‘wriggling redly’. Of course, this perception of different wrigglings as characteristic of different environmental stimuli would not be available to the organism itself since it does not have the necessary cognitive apparatus for this kind of secondary observation, (basically an apparatus in which this sensorimotor engagement was represented in some way). If it were to evolve such a capacity however, then it would be able to not only actively participate in the production of sensation but also to have perception of this sensorimotor engagement. It would not only be part of what happens it would also perceive the feeling of what happens.
DAMASIO, A. R. (2000) The feeling of what happens: body and emotion in the making of consciousness, London, Heinemann.
HUMPHREY, N. (2000) The privatization of sensation. IN HUBER, L. & HEYES, C. (Eds.) The Evolution of Cognition. Cambridge, MA, USA, MIT Press.