Certain "repetitive" activities may not represent core features of autistic disorder and may be equivalent to normal motor and cognitive behaviors, as seen during typical development.

Abnormal pain reactivity is often reported by the parents of children with autistic disorder (AD). This is an interesting feature because it could be related to some neurochemical findings frequently reported in autism. The aim of the present study is to report the preliminary findings about pain reactivity in children with autism, and to relate them to serotoninemia. We studied 77 subjects with “primary” AD. Reports of each child's pain reactivity were obtained through a structured interview with the child's parent. In 44 of the 77 children, serotonin blood levels were measured. We found an abnormal pain reactivity in children with autistic disorder when compared with non-autistic children, matched for age, sex, and socio-economic level. The pain reactivity showed a significant correlation with the serotoninemia levels. The data obtained by the present study are interesting, although they must be considered with careful attention, both for the sample size and for methodological difficulties. In fact, in studying this disorder, only the parents' insight can be of help