No evidence for impaired perception of biological motion in adults with autistic spectrum disorders

A central feature of autistic spectrum disorders (ASDs) is a difficulty in identifying and reading human expressions, including those present in the moving human form. One previous study, by Blake et al. (2003), reports decreased sensitivity for perceiving biological motion in children with autism, suggesting that perceptual anomalies underlie problems in social cognition. We revisited this issue using a novel psychophysical task. 16 adults with ASDs and 16 controls were asked to detect the direction of movement of human point-light walkers which were presented in both normal and spatially scrambled forms in a background of noise. Unlike convention direction discrimination tasks, in which walkers walk 'on the spot' while facing left or right, we added translatory motion to the stimulus so that the walkers physically moved across the screen. Therefore, while a cue of coherent, translatory motion was available in both the normal and scrambled walker forms, the normal walker alone contained information about the configuration and kinematics of the human body. There was a significant effect of walker type, with reduced response times and error when the normal walker was present. Most importantly, these improvements were the same for both participant groups, suggesting that people with ASDs do not have difficulty integrating local visual information into a global percept of the moving human form. The discrepancy between these and previous findings of impaired biological motion perception in ASDs are discussed with reference to differences in the age and diagnosis of the participants, and the nature of the task.