"Autism is the most genetic of the neuropsychiatric disorders. So the child seems genetically impaired in his or her ability to interact, and the question is what is the nature of the impairment. There are lots of ideas about this. One is that autistic children don't process faces normally, which interferes with their interactions with people. Another is that they don't have the special interest in biological as opposed to inanimate things that normal children have. And another idea is that they can't figure out what's going on in somebody else's mind - called mind blindness or a 'theory of mind problem'.
I think it is very unlikely that any of those are the primary problem. I think a more likely explanation is that there is a problem with attention - a particular type of attention problem. There's increasing evidence that these children have what's called sticky attention, which is a problem with attention disengagement. When autistic children are focused on something, it's very hard to disconnect them and get them to focus on something else. So shifting attention from one thing to another seems to be a problem."