Foveal analysis and peripheral selection during active visual sampling

Abstract

Human vision is an active process in which information is sampledduring brief periods of stable fixation in between gaze shifts.Foveal analysis serves to identify the currently fixated object andhas to be coordinated with a peripheral selection process of thenext fixation location. Models of visual search and scene perception typically focus on the latter, without considering fovealprocessing requirements. We developed a dual-task noise classification technique that enables identification of the informationuptake for foveal analysis and peripheral selection within a singlefixation. Human observers had to use foveal vision to extractvisual feature information (orientation) from different locationsfor a psychophysical comparison. The selection of to-be-fixatedlocations was guided by a different feature (luminance contrast).We inserted noise in both visual features and identified the uptakeof information by looking at correlations between the noise atdifferent points in time and behavior. Our data show that fovealanalysis and peripheral selection proceeded completely in parallel.Peripheral processing stopped some time before the onset of aneye movement, but foveal analysis continued during this period.Variations in the difficulty of foveal processing did not influencethe uptake of peripheral information and the efficacy of peripheralselection, suggesting that foveal analysis and peripheral selectionoperated independently. These results provide important theoretical constraints on how to model target selection in conjunctionwith foveal object identification: in parallel and independently.