FACIAL RESPONSIVENESS TO ODORS IN NORMAL AND PERVASIVELY DEVELOPMENTALLY DISORDERED CHILDREN

The facial responsiveness of in mutic children with pervasive developm ental disorder (PDD) and 10 normal (N) children matched for sex and ch ronological age were covertly videotaped while presented with a set of odours contrasted in hedonic valence. Hedonic ratings of the stimuli were obtained both from the group of N subjects and a panel of adults. Two methods were used to measure facial responses in the same subject s. The first method consisted in an analysis of facial movements with the Facial Action Coding System. Results show that PDD and N subjects displayed distinct action units in response to unpleasant odours. PDD subjects typically displayed muscular actions indexing negative experi ence, while N subjects showed more smiles. With the second method, odo ur-elicited facial behaviour was rated by a panel of observers, who we re asked to judge whether the subjects were exposed a pleasant, neutra l or unpleasant smell. The facial responses to unpleasant odours were classified more accurately in PDD than in N subjects. These findings s uggest a functional ability to sense the hedonics attached to odours, but a deficit of socialization of hedonic facial displays in developme ntally disordered subjects.