Difficulty in perceiving and interpreting other people's actions is a core feature of autism spectrum disorder (ASD). Maggie Shriffrar and her colleagues at Rutgers University are investigating whether some of the social difficulties experienced by people with ASD arise from a lack of visual sensitivity to the movements of other people.
The Shiffrar lab is conducting a series of studies to determine how, and how well, observers with ASD detect and analyze the actions of other people. Thus far, they have documented that typical observers demonstrate greater visual sensitivity to human movement than to the movements of objects and animals. This finding is consistent with the hypothesis that the human visual system is typically tuned for the detection and analysis of socially relevant information. To determine whether observers with ASD also show enhanced visual sensitivity to human movement, we asked three groups of participants (young adults with high-functioning autism or Asperger's Syndrome, typically developing young adults, and typically developing children) to view movies of a moving person or a moving object. The motion information in half of the movies was scrambled so that coherent motion was absent. On each trial, observers looked at one movie and judged whether or not coherent motion was present. Whereas typically developing children and age-matched typical adults showed greater visual sensitivity to human motion than to object motion, young adults with ASD showed equal visual sensitivity to human and object movement. Similarly, data from a follow-up study show that observers with ASD do not have greater visual sensitivity to human versus animal movement, whereas typical observers are more sensitive to human movement.
These results are consistent with the hypothesis that people with ASD have visual systems that are not tuned for the detection of socially relevant information.
A second goal of the Shriffrar research team is to determine why autistic traits correlate with atypical patterns of visual sensitivity to other people's actions. Thus far, their results suggest two partial explanations. First, typical observers use information from their own motor systems to help interpret other people's movements. In individuals with Asperger's Syndrome, the researchers have found significant correlations between the observer's own motor skill and visual sensitivity to other people's actions, suggesting that compromised motor input to the visual system may hinder observers with ASD. Second, in typical observers, the visual analysis of other people's actions is closely linked to emotional processes. For example, we have enhanced visual sensitivity to the movements of angry people. Data from the Shriffrar lab suggest that observers with ASD do not show enhanced visual sensitivity to angry human movements. This result is consistent with neural abnormalities in the areas involved in the detection of human movement and the detection of threats as well as in the connections between these areas. Taken together, these results suggest that differences in social and motor processes help to define atypical patterns of visual sensitivity to human movement in observers with ASD.
Shriffrar and colleagues hope that their findings will contribute to therapeutic applications and more effective training programs to help people with autism recognize and respond to social cues.