Perceptual decisions are biased by recent perceptual history—a phenomenon termed 'serial dependence.' Here, we investigated what aspects of perceptual decisions lead to serial dependence, and disambiguated the influences of low-level sensory information, prior choices and motor actions. Participants discriminated whether a brief visual stimulus lay to left/right of the screen center. Following a series of biased ‘prior’ location discriminations, subsequent ‘test’ location discriminations were biased toward the prior choices, even when these were reported via different motor actions (using different keys), and when the prior and test stimuli differed in color. By contrast, prior discriminations about an irrelevant stimulus feature (color) did not substantially influence subsequent location discriminations, even though these were reported via the same motor actions. Additionally, when color (not location) was discriminated, a bias in prior stimulus locations no longer influenced subsequent location discriminations. Although low-level stimuli and motor actions did not trigger serial-dependence on their own, similarity of these features across discriminations boosted the effect. These findings suggest that relevance across perceptual decisions is a key factor for serial dependence. Accordingly, serial dependence likely reflects a high-level mechanism by which the brain predicts and interprets new incoming sensory information in accordance with relevant prior choices.

Autism spectrum disorder (ASD) manifests sensory and perceptual atypicalities. Recent theories suggest that these may reflect a reduced influence of prior information in ASD. Some studies have found reduced adaptation to recent sensory stimuli in ASD. However, the effects of prior stimuli and prior perceptual choices can counteract one-another. Here, we investigated this using two different tasks (in two different cohorts): (i) visual location discrimination, and (ii) multisensory (visual-vestibular) heading discrimination. We fit the data using a logistic regression model to dissociate the specific effects of prior stimuli and prior choices. In both tasks perceptual decisions were biased toward recent choices. Notably, the 'attractive' effect of prior choices was significantly larger in ASD (in both tasks and cohorts), while there was no difference in the influence of prior stimuli. These results challenge theories of reduced priors in ASD, and rather suggest an increased consistency bias for perceptual decisions in ASD.

Perceptual decisions are biased by recent perceptual history -a phenomenon termed 'serialdependence.' Using a visual location discrimination task, we investigated what aspects of perceptual decisions lead to serial dependence, and disambiguated the influences of low-level sensory information, prior choices and motor actions on subsequent perceptual decisions.Following several biased (prior) location discriminations, subsequent (test) discriminations were biased toward the prior choices, even when reported via different motor actions, and when prior and test stimuli differed in color. By contrast, biased discriminations about an irrelevant stimulus feature did not substantially influence subsequent location discriminations. Additionally, biased stimulus locations, when color was discriminated, no longer substantially influenced subsequent location decisions. Hence, the degree of relevance between prior and subsequent perceptual decisions is a key factor for serial-dependence. This suggests that serial-dependence reflects a high-level mechanism by which the brain predicts and interprets incoming sensory information in accordance with relevant prior choices.

Autism spectrum disorder (ASD) manifests sensory and perceptual atypicalities. Recent theories suggest that these may reflect a reduced influence of prior information in ASD. Although many studies have not found reduced long-term priors ASD, some have found reduced adaptation to recent sensory stimuli. However, the effects of recent prior stimuli and prior perceptual choices can counteract one-another. Here, we investigated this using two different tasks (in two different cohorts): (i) visual location discrimination, and (ii) multisensory (visual-vestibular) heading discrimination. We fit that data using a logistic regression model to dissociate the specific effects of prior stimuli and prior choices. In both tasks/cohorts perceptual decisions were biased toward recent choices and away from prior stimuli. Notably, the ‘attractive’ effect of prior choices was significantly larger in ASD, while there was no difference in the influence of prior stimuli (in both tasks). These results challenge theories of reduced priors in ASD, and rather suggest an increased consistency bias for perceptual decisions in ASD.

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