Differential effects of top-down crossmodal attention on subjective timing of semantic and syntactic violations.

Prior knowledge violations about the world's consistency can distort subjective time perception. Scenes containing contextually irrelevant objects (i.e., semantic violations) are typically underestimated in duration (i.e., perceived shorter), whereas those violating basic spatial norms (i.e., syntactic violations) are often overestimated (i.e., perceived longer) as compared to standard scenes without violations. Previous research has shown that directing attention toward such violations through low-level attentional manipulations can dilate their perceived duration. However, it remains unclear whether top-down attentional manipulations can produce a similar effect, especially given evidence suggesting a reduced influence of top-down attention in the presence of semantic and syntactic violations. Here, we examined the effect of top-down attention via crossmodal stimulation on time estimations of both semantic and syntactic violations. We utilized a temporal oddball paradigm where participants viewed sequences of naturalistic scenes with or without violations (semantic or syntactic). Each sequence included a violation scene (i.e., oddball) paired with white noise (i.e., control) or a sound that matched (i.e., congruent) or mismatched (i.e., incongruent) the target violation to manipulate top-down attention via crossmodal stimulation. Participants judged whether the oddball's duration was shorter or longer than the no violation scenes. Analyses showed no differences in the perceived duration of syntactic violations scenes across the different types of auditory stimulation, a finding that is attributed to a diminished top-down attentional effect on scenes with syntactic violation given possibly to their higher perceptual load. Semantic violations, however, demonstrated sensitivity to crossmodal influence, where incongruent sound pairings led to interval overestimations as compared to congruent pairings. This suggests that crossmodal conflict enhanced attention toward the violations, leading to longer perceived durations. Our findings highlight the distinct susceptibility of semantic versus syntactic violations to top-down modulation in the temporal domain.