Researchers in Italy studied 20 high functioning children with autism compared to neurotypical children regarding picture/ shape identification with and without shadows present. The presence of shadows hampered the children with autism's ability to recognize the objects. The researchers hypothesize that the children may hyperfocus on the shadows distracting their attention. The researchers recommend using multiple light sources for children with autism to reduce shadows.
On an additional note, during the study, the researchers observed that the children with autism had strict routines regarding snack time i.e. food placement, type of snack, etc.
Reference: Charles Q. Choi, LiveScience Contributor. Shadows Distract Autistic Children. Retreived on the web on 5/21/2010 from http://www.livescience.com/health/Shadows-Distract-Autistic-Children-100520.html