dence that children with autism have higher levels of arousal than other children. In fact, in reaction to adult affect, there was much less response, both behaviorally and physiologically, from the children with autism than from carefully matched controls.

This study, and other research from Sigman’s laboratory, emphasized the lack of social orienting to other’s faces. Other investigators have also have begun to ask whether social orienting is particularly impaired in autism (Dawson et al., 1998). The social orienting question is currently compelling because of possible links to particular brain structures that play a very specific role in orientation to other people, including awareness of eye contact and directionality of gaze (as reviewed in Baron-Cohen et al., 1999). Whether social orienting represents one of a variety of social behaviors that are impaired in autism, or whether it represents the pivotal social behavior that leads to the development of a much wider social repertoire, remains to be seen.

COMMONALTIES AND INDIVIDUAL DIFFERENCES

Given that children with autism, as a group, demonstrate widely differing levels of skills and of severity of symptoms, discussion of commonalties must occur at a general level. By definition, children with autism demonstrate impairments in relationships to peers, the use of nonverbal communicative behaviors within their social exchanges, the use of imitation, and symbolic or dramatic play. Peer interactions, and indeed social interactions in general, are characterized by low rates of both initiation and response. This is most marked in interactions for the purpose of sharing experiences and establishing joint foci of attention (Peterson and Haralick, 1977; Mundy et al., 1990; Mundy et al., 1987; Wetherby and Prutting, 1984; Corona et al., 1998). The use of nonverbal communication, including gestures and emotional expressions, is affected in young children, both expressively and receptively. As described in these papers, children with autism use fewer nonverbal gestures and a more limited range of facial expressions in their communications than children with other types of developmental disabilities of the same developmental and chronological age. Children with autism appear to pay less attention to other people’s emotional displays than do comparison groups and to demonstrate fewer acts of empathy or shared emotion. Children with autism also demonstrate less imitation of other people’s actions, movements, and vocalizations (DeMyer et al., 1972; Stone et al., 1997) .

Yet there are wide-ranging differences within the group of children with autism in their social interests and behaviors. In terms of general sociability, Wing and Gould (1979) suggested three subgroupings of children with autism based on social interests: aloof, passive, and active but odd. Aloof was defined as indifferent in all situations, particularly



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