Saccadic and perceptual performance in visual search tasks. I. Contrast detection and discrimination.

Abstract

Humans use saccadic eye movements when they search for visual targets. We investigated the relationship between the visual processing used by saccades and perception during search by comparing saccadic and perceptual decisions under conditions in which each had access to equal visual information. We measured the accuracy of perceptual judgments and of the first search saccade over a wide range of target saliences [signal-to-noise ratios (SNRs)] in both a contrast-detection and a contrast-discrimination task. We found that saccadic and perceptual performances (1) were similar across SNRs, (2) showed similar task-dependent differences, and (3) were well described by a model based on signal detection theory that explicitly includes observer uncertainty [M. P. Eckstein et al., J. Opt. Soc. Am. A 14, 2406 (1997)1]. Our results demonstrate that the accuracy of the first saccade provides much information about the observer's perceptual state at the time of the saccadic decision and provide evidence that saccades and perception use similar visual processing mechanisms for contrast detection and discrimination.