A recent study explains why one of the hallmarks of autism in children is apparent non-responsiveness to the people around them: The brains of those with autism don't process facial expressions.

Children in an experiment conducted by researchers from UCLA were hooked up to a functional magnetic resonance imaging (fMRI) machine and shown pictures of faces that expressed happiness, anger, fear and emotional neutrality. FMRI images of the brains of non-autistic children showed considerable reactivity in the area that recognizes differences in people's expressions. But the fMRI images from autistic children showed almost no activity.

"They don't pick up what's going on," says Mari Davies, a UCLA graduate student of psychology and a leader of the research team, whose study was presented in May at the International Meeting for Autism Research in Seattle. "They miss the nuances, the body language and facial expressions. Sometimes they miss the big picture and instead focus on minor, less socially relevant details. That, in turn, affects interpersonal bonds."