Visual perception

Background

An important research question is whether there are fundamental differences in perceptual systems in autism. There are several reasons for thinking that this is a possibility. One is that many individuals with autism report abnormal sensory and perceptual experiences. Another is the common observation of acute attention to incidental stimuli in the environment. A third is that individuals with autism show abnormal attention to faces, either by looking less at faces than is typical or looking at different regions of the face, such as the mouth raher more than the eye region. One suggestion has been that individuals with autism show enhanced perception of individual features and/or poor perception of global configural stimuli.

Local and global perception

Studies assessing local and global processing have employed hierarchical stimuli, in which a large global shape is comprised of small local shapes. On the whole, two types of task have been employed: a selective attention procedure and a divided attention procedure. In the selective attention procedure, participants are cued to attend to either the global or the local shapes. Studies using this procedure have found that individuals with autism show typical global/local perception by responding more quickly and accurately to the global than the local shape. However, in divided attention procedures, in which participants are required to attend to both local and global levels to detect a target shape, individuals with autism have shown enhanced local processing. These studies therefore raise the possibility that unless individuals with autism are directly cued to attend to global configurations, they will tend to process the local level preferentially. However, this does not mean that local features are perceived differently in autism. Rather, it suggests that attentional mechanisms that prioritise processing of global and local levels may operate differently in autism. Recent studies conducted by the LaRA have shown that local and global perception and the development of local and global representations is typical in individuals with autism, as is configural processing.

Movement perception

Children with autism often show excessive interest in movement, such as spinning the wheels of a toy car, raising the possibility that movement perception may be different in autism. Several studies have now demonstrated impairments in complex motion processing, particularly when moving visual information requires integration. A recent finding in the LaRA, which may be related to this issue, is that children with autism process dynamic stimuli differently to static stimuli. We are now considering the extent to which this may result from early perceptual systems, such as the magnocellular system, or abnormal attentional modulation of perceptual systems.

Related reading

Mottron, L., & Burack, J. (2001). Enhanced perceptual functioning in the development of autism. In: Burack, J.A., Charman, A., Yirmiya, N. & Zelazo, P.R. (Eds). Development and Autism: Perspectives from theory and research. Lawrence Erlbaum Associates, New Jersey.

Plaisted, K.C. (2001). Reduced generalization: An alternative to weak central coherence. In: Burack, J.A., Charman, A., Yirmiya, N. & Zelazo, P.R. (Eds). Development and Autism: Perspectives from theory and research. Lawrence Erlbaum Associates, New Jersey.

Ozonoff, S., Strayer, D. L., McMahon, W. M., & Filloux, F. (1994). Executive function abilities in autism and Tourette syndrome: An information processing approach. Journal of Child Psychology and Psychiatry and Allied Disciplines, 35(6), pp.1015-1032.

Mottron, L., Burack, J. A., Iarocci, G., Belleville, S., & Enns, J. T. (2003). Locally oriented perception with intact global processing among adolescents with high-functioning autism: Evidence from multiple paradigms. Journal of Child Psychology and Psychiatry and Allied Disciplines, 44(6), pp.904-913.

Plaisted, K. C., Swettenham, J., & Rees, L. (1999). Children with autism show local precedence in a divided attention task and global precedence in a selective attention task. Journal of Child Psychology and Psychiatry and Allied Disciplines, 40(5), pp.733-742.

Plaisted, K., Saksida, L., Alcantara, J., & Weisblatt, E. (2003). Towards an understanding of the mechanisms of weak central coherence effects: Experiments in visual configural learning and auditory perception. Philosophical Transactions of the Royal Society, series B, 358(1430), pp.375-386.

Plaisted, KC, Dobler, V., Bell, S., & Davis, G. (submitted). The microgenesis of global perception in autism. Submitted to Journal of Autism and Developmental Disorders.

Bertone, A., Mottron, L., Jelenic, P., & Faubert, J. (2003). Motion perception in autism: A "complex" issue. Journal of Cognitive Neuroscience, 15(2), pp.218-225.

Spencer, J., O'Brien, J., Riggs, K., Braddick, O., Atkinson, J., & Wattam-Bell, J. (2000). Motion processing in autism: evidence for a dorsal stream deficiency. NeuroReport, 11(12), pp.2765-2767.

Milne, E., Swettenham, J., Hansen, P., Campbell, R., Jeffries, H., & Plaisted, K. (2002). High motion coherence thresholds in children with autism. Journal of Child Psychology and Psychiatry and Allied Disciplines, 43(2), pp.255-263.