A mechanism for the direct perception of change: the example of bacterial chemotaxis

The relationship between the behavior of single-celled organisms and cognition in higher animals is explored. Recent research and theory in bacterial chemotaxis are presented, together with a discussion of the implications of chemotaxis for perceptual theory. A number of parallels between chemotaxis and perception in higher organisms are drawn. It is suggested that Koshland's model of the chemical processes controlling chemotaxis is an example of a mechanism for direct perception of change and can help elucidate Runeson's work on 'smart mechanisms' of perception. It is argued, more generally, that the growing body of knowledge about the perceptual activities of lower organisms should be used to broaden the factual base on which theories of perception are constructed: eg explication of perceptual parallels between humans and lower organisms should help clarify the nature of these phenomena in humans and, perhaps, help in the development of theories of greater generality. Also, the debate between direct and indirect theories of perception may be advanced by analysis of the specific mechanisms used by lower organisms. Contrasts to mediated perception are pointed out and arguments for the relative simplicity and explanatory power of theories of direct perception are provided.