Reciprocal roles of crowding and serial dependence on visual perception

Visual perception arises from the interplay between current and prior sensory inputs. Two perceptual phenomena-serial dependence and visual crowding-result from the mandatory integration of retinal information across time and space, respectively. This study investigated, for the first time, their functional relationship for orientation and brightness discrimination tasks. Participants performed orientation and brightness discrimination tasks (blocked) on peripheral targets surrounded by distractors of varying color, orientation, and proximity. Both serial dependence (the influence of prior stimuli on current judgments) and visual crowding (impaired peripheral recognition caused by nearby distractors) were observed. Similar double dissociations in task and stimulus specificity emerged for both phenomena, suggesting functional links mediated by distinct processing mechanisms for brightness and orientation judgments. Additionally, the two effects interacted: crowding reduced serial dependence on subsequent trials, indicating that spatial information is prioritized over temporal information when spatial redundancy is high. Conversely, serial dependence increased crowding for orientation judgments, while for brightness judgments, serial dependence operated additively without affecting crowding. These interactions were spatially specific, occurring only when targets appeared in the same location across consecutive trials. Notably, a positive correlation between crowding and serial dependence was found exclusively for orientation judgments and only when targets appeared at the same location across trials. The reciprocal interaction and positive correlation between serial dependence and crowding observed for orientation judgments indicate that that these processes are intrinsically linked, possibly via a common neural mechanism. In contrast, for brightness judgments, the unilateral effect of crowding on serial dependence—along with the absence of correlation-indicates distinct neural mechanisms. Here, brightness crowding likely precedes serial dependence, reflecting a prioritization of spatial redundancy minimization over temporal stabilization. These findings suggest that the brain strategically integrates spatial and temporal information through distinct yet overlapping mechanisms, balancing spatial precision with temporal stability based on task demands and stimulus characteristics.