Plm_045_c003 87..145

In 1960, J. J. Gibson reviewed technical uses of the term stimulus and found that it did not have a consistent agreed-upon definition, but instead connoted several diVerent conceptions of ‘‘stimulating’’ an organism. Most of those conceptions did, however, have a property also found in the word’s original uses: A stimulus is a temporally discrete, momentary happening in the life of an organism. Challenging this intuition, Gibson’s ecological psychology assumes at its foundation the continuity of the stimulation in the surrounding environment. What this means is that the ‘‘flowing array of stimulus energy,’’ as Gibson called it, is never presegmented into easily defined independent chunks, or ‘‘stimuli,’’— even though we feel as though we perceive it that way. Before Gibson, Dewey (1986) famously made a similar point in his influential critique of the reflex arc concept. The reflex arc concept was a relatively new idea, framing the questions of psychology in terms of causal arcs among stimulus, mental event, and response. Essentially, studying the causal arcs between just the former two, or the latter two, was considered a legitimate scientific enterprise in and of itself. In contrast, treating the