A region of the brain that controls language is more extensively curved in children with autism than in those with Asperger syndrome, according to a study published in the Journal of Child Neurology. The findings offer preliminary biological evidence that Asperger syndrome, a disorder on the autism spectrum, is distinct from high-functioning autism.

Individuals carrying an extra copy of the genetic region that’s missing in Williams syndrome — which causes mental retardation and a hyper-friendly personality — have language impairments and other autism-like social difficulties, according to a wave of new research on this duplication syndrome.

Children with Williams syndrome — a rare genetic disorder that leads to mental retardation and overt friendliness — hold stereotypes based on gender, but not race, according to a report published in Current Biology. Because those with Williams syndrome don’t have social fear, the study suggests racial stereotypes are based partly on fear.

Studying the relatively well-defined genetics of Williams syndrome may help unravel the poorly understood genetic and neurobiological roots of autism, researchers say.