This grant for two years is on visual perception. The function of the visual system is to generate representations of the environment that will support adaptive behavior. It is important for certain "visual constancies" to be developed, so that for example a small object nearby is not mistaken for a larger object farther away. For an observer to compute a visual representation of the size of an object, both the projected size of the object and the viewing distance must be considered. Similarly, other "visual constancies" of objective shape, depth and velocity must involve considering features other than the projected view of the object. One explanation for considering these other features is that mental "attention" is required for adequate processing, in addition to some "automatic" processing components that work in the absence of attention (known as "pre-attentive" processing). This two-stage model suggests that two-dimensional properties (size, shape and position) do not require attention, but the 3- dimensional construct does depend on attention, operating on the 2-D representation. This project will assess the computational steps for producing such representations, to see whether a two- stage model of processing is required for 3-D analysis. Human observers will be presented with visual stimuli along with different kinds of attention-distractors. Then they will be given a test stimulus and asked if it is the same or different from the original. If a two-stage process occurs, distraction of attention is expected to cause false positive responses. Tests will concentrate on shape-at-a-slant, and size-at-a-distance. A second set of experiments will utilize search time necessary to distinguish such targets in a multiple array. Here longer search times are expected to reflect the longer processing required for attentive steps, compared to the pre-attentive steps. This research uses a novel approach, and has important implications for understanding visual space perception, and the field of computational vision. It is likely to have impact on concepts of the role of attention in perception in general, and also on design of artificial vision systems.
