People with autism tend to have difficulties remembering faces, processing facial expressions and knowing which components of faces convey especially important communicative information. However, it is unknown why people with autism have these difficulties. One theory is that because of their lack of interest in socialising autistic people just do not develop the expertise in 'face processing' that other people do. Another theory is that people with autism have difficulty in perceiving all complex objects, not just faces. A study of 60 children by researchers at the University of Pittsburgh tested them on their ability to recognise different faces and different imaginary creatures called greebles which were designed to be subtly different but not to convey any social information through expressions or body language. Compared to the healthy control group the autistic children found it much harder to differentiate between the faces and the greebles suggesting that it was complicated objects rather than faces per se they had trouble processing.
Scherf, K. Suzanne ... [et al] - Atypical development of face and greeble recognition in autism Journal of Child Psychology and Psychiatry August 2008, 49(8), 838-847