Abstract
Background. Compared to typically developed perception, ASD perception relies more on bottom-up, sensory input. In a Bayesian framework, perceptual decisions depend on three information sources: expectation (prior), sensory evidence (likelihood), and reward (cost function). There is a growing debate about whether atypical perception in ASD is due to changes in prior information or changes in likelihood. Inconsistent results may be due to variations in tasks and sampled populations. Importantly, decisions also involve decision rules (criteria) that may incorporate any of these information sources. Nevertheless, it is unknown whether ASD individuals appropriately set their choice criteria. Moreover, it is unknown whether ASD decision processes in basic perception are mirrored in metacognition. Here, we address these issues with a systematic investigation that tests the effects of prior belief and likelihood on decision criteria in perceptual and metacognitive judgments. Method. Observers performed an orientation categorization task by simultaneously reporting orientation category and confidence. Stimulus orientation was drawn from 2 gaussian distributions with means μA = -4 ̊ and μB = 4 ̊, and standard deviations 𝜎A = 𝜎B = 5 ̊, which induced an overlap between the two distributions. We manipulated prior by varying the base-rate probability of each category and likelihood by varying stimulus contrast. Results. Both groups shifted decision criteria to favor the category with the higher base rate. Furthermore, people with ASD, like controls, shifted their decision criteria to favor the more probable category more when stimulus contrast was low. Finally, the ASD group showed typical abilities in metacognitively assessing their performances. Conclusion. Contrary to recent views, individuals with ASD integrate prior expectation with sensory evidence similarly to typically developed individuals. Both groups integrate prior with likelihood in a manner consistent with the Bayesian theory. In the context of a visual task, the metacognitive abilities also appear to be preserved.