From the point of view of neuropsychology there are no gestures. In other words, gestures are not a coherent category. By this I mean that there is no center for gestures in the brain, there is no form of brain damage which selectively abolishes the, ability to gesture. Rather, different kinds of gestures are differentially affected in different circumstances, never primarily but always as part of a more general, underlying processing deficit. That is important because to my mind the brain is the touchstone of the biological reality of categories. In the case of language the brain tells us that category is real because there are parts of the brain which subserve language, and one can suffer a selective language loss. Gestures cannot be compared to language in that way. They comprise bits and pieces of, different behaviors which we have chosen so to name. The same applies to semiotics. There is no brain center for semiotic behavior. There is no lesion which strips acts of meaning or of signaling value, leaving their representations preserved in the brain. So we are dealing with categories which are useful abstractions but do not delineate packages of the mind. Rather than define gesture, which for these reasons is a sterile thing to do, we shall discuss a variety of behaviors which people have called gestures.
First, I would like to present a classification of gestures. It will not be the. same as A. R. Lecours' (this volume), but only because a different description better serves my present purpose. No one taxonomy is best. A particular taxonomy may be useful for the points one wishes to make. One may first distinguish between movements serving the homeostasis of the body ( Yakovlev's ereismokinetic level), and movements pointed toward external space. And the latter are divided into the obvious sequential elements of orienting toward, locomoting to, and then instrumentally acting upon whatever is there ( Kinsbourne,