Awareness threshold for face processing in individuals with autism

Numerous studies have demonstrated face processing deficits in individuals with autism, which have been attributed to amygdala dysfunction. These deficits suggest a reduced salience of faces and use of a feature-based rather than configural face processing strategy. The present study investigated speed of face processing in individuals with autism. Given the role of the amygdala in implicit processing of faces, and the greater processing time required for feature-based than configural strategies, it was predicted that individuals with autism would demonstrate slower face processing than controls. Participants viewed a target photograph of a face or an object displayed on a computer screen at exposure durations ranging from 10 msec to 160 msec. Participants were then shown two alternatives and were asked to indicate which one matched the target. Foils were photographs depicting a different facial identity, facial emotion, or object. The awareness threshold for a given task was defined as the exposure duration at which a participant was able to consistently identify the target. Analysis of variance revealed a significant main effect of task, such that the awareness threshold for identification of objects was lower than for both facial identity and emotion in both individuals with autism and controls. A nearly significant main effect of diagnostic group was also found, such that individuals with autism required a longer exposure duration across tasks. No face-specific deficit was found. These results are discussed in relation to the amygdala theory of autism. In a separate comparison, typically developing adults were found to be faster than children, supporting previous findings of a developmental progression in speed of face processing. Adults with autism were not faster than children with autism, suggesting a failure to develop efficient face processing strategies with age. Finally, cross-cultural comparisons demonstrated that typically developing Japanese participants were faster at visual processing than were American participants, and that Japanese participants with autism did not demonstrate the same processing deficit as did American participants. These results are discussed as attributable to chance error, methodology, or possible subtle cultural differences.