She still seems angry: inflexibility in updating emotional priors in autism

Abnormalities in the use of prior information of basic perceptual stimuli have been observed in people with autism spectrum disorder (ASD), yet it remains unclear whether and how these abnormalities extend to complex stimuli and emotional stimuli in particular. Here, we compared people with ASD and neurotypicals in their ability to acquire and then update a prior of facial expressions. Participants performed a two-interval forced choice discrimination task between two facial expressions presented in succession. To examine the acquisition of the prior, we used the paradigm of “regression to the mean”, in which discrimination between faces is modified according to the mean statistics accumulated during the experiment. In the first part of the experiment, participants were exposed to facial expressions sampled from a normal distribution around one average prior (sad/angry). In the second part of the experiment, the average changed to a different prior (angry or sad accordingly). We found a significant difference in performance between groups in the use of the priors. While both groups acquired the first prior, only the neurotypicals acquired the second prior. Carrying out a trial-by-trial analysis further demonstrated the effects of the recent trials and overall mean statistics in both experiment parts on the performance of neurotypicals. In ASD, in contrast, the overall mean statistics was used in the first part of the experiment; however, when the overall mean was updated in the second part, ASD only relied on recent trials. These findings suggest that ASD have a difficulty in updating an acquired prior of an emotional facial expression and shed light on the social behavior of people with autism.