ELSC Seminar Series

Conscious versus Implicit Perception of Categories and Sets

I shall discuss why’s and how’s of categorization, and the relationship of categorization to perceiving set statistics more generally. These two perceptual phenomena share a common paradox: Category exemplars share sufficient features to allow recognizing them as category members and to respond similarly to them (a dog is a dog), but each exemplar is different, or we would be left with a category of one, a useless tautology. Similarly, in ensemble perception, set members have to be similar enough to be included in a single ensemble and to perceive their summary statistics, but they have to be different or we would be left with a set of identical elements, with meaningless statistics. We are currently interested in the involvement of attention in categorization and in ensemble perception. We compare explicit, conscious perception, when performing a visual task demanding organization of visual images and judging their statistics, versus implicit, automatic perception of the same properties of the set of stimuli, when attention is occupied in performance of a second (primary) task. We ask if the underlying visual processes are the same in the two cases. Do observers do better when they attend and try harder? Do these percepts depend on the same or on different cortical processes? Comparing the performance of hundreds of observers in the different task conditions helps decide between these alternatives.