UC Berkeley

From moment to moment, we perceive objects in the world as continuous despite fluctuations in their image properties due to factors like occlusion, visual noise, and eye movements. The mechanism by which the visual system accomplishes this object continuity remains elusive. Recent results demonstrate that the perception of low-level stimulus features such as orientation and numerosity is systematically biased (i.e. pulled) towards visual input from the recent past. The spatial region over which current orientations are pulled by previous orientations is known as the continuity field, which is temporally tuned for the past 10-15 seconds. This perceptual pull could contribute to the visual stability of low-level features over short time periods, but it does not address how visual stability occurs at the level of complex objects or during visual discontinuities. Here, we examined whether the visual system facilitates stable perception by biasing current perception of objects towards recently seen objects, and whether it operates across disruptions in visibility. First, we used psychophysics to show that the perception of face identity is systematically biased towards identities seen up to several seconds prior, even across changes in viewpoint. This perceptual bias did not depend on subjects’ prior responses or on the method used to measure identity perception. Next, we tested whether this serial dependence, or positive perceptual pull, helps stabilize perceived expression. To test this, observers judged random facial expressions (ranging from happy to sad to angry). We found a pull in perceived expression toward previously seen expressions, but only when the 1-back and current face shared the same identity. Finally, we examined whether the continuity field helps maintain perceived object identity during occlusion. Specifically, we found that the perception of an oriented Gabor that emerged from behind an occluder was significantly pulled towards the random (and unrelated) orientation of the Gabor that was seen entering the occluder. Importantly, this serial dependence was stronger for predictable, continuously moving trajectories, compared to unpredictable ones or static displacements. While this serial dependence in object perception manifests as a misperception, it is adaptive: visual processing echoes the stability of objects in the world to create perceptual continuity. These results provide further evidence for the existence of an object-selective continuity field that helps maintain perceived object stability over time and across visual noise or disruptions.