Abstract
Despite a noisy and ever-changing visual world, our visual experience is remarkably stable and continuous over time. One way that the visual system may promote such stability is through the introduction of serial dependence to visual perception: by biasing the current percept toward what was seen previously, the brain could compensate for variability in visual input that might otherwise disrupt perceptual continuity. Here, we tested for serial dependence in visual perception using an orientation judgment task. Subjects reported the orientations of sequentially presented suprathreshold, high contrast gratings, which were separated in time by several seconds. We found that on a given trial, a subject’s perception of the grating orientation reflected not only the currently viewed stimulus, but also a systematic attraction toward the orientations of the previously viewed stimuli. This perceptual attraction extended over several trials, and displayed clear tuning to the difference in the orientations of the sequential stimuli. Furthermore, serial dependence in perceived orientation was spatially specific, occurring most strongly within a constant retinal location, somewhat less strongly across different retinal locations at the same head-centered position, and only weakly across changes in both retinal and head-centered location. Several control experiments showed that the perceptual serial dependence we report cannot be explained by known effects of priming, hysteresis, visual short-term memory, or expectation. Our results reveal a systematic influence of recent visual experiences on perception at any given moment: visual percepts, even of unambiguous stimuli, are attracted toward what was previously seen. We propose that such serial dependence helps to maintain continuity in the perception of object and scene properties in the face of a dynamic and noisy environment.
This work was supported by NEI grant T32EY015387 (J.F.) and NIH grant EY018216 (D.W.).