Children with neurodevelopmental disorders often have significant impairments in social adaptation and social communication, which impact their relationships with others. This research will examine the neural, psychophysiplogical, and information processing bases of major differences in social affective behavior in children with neurodevelopmental disorders of different nature and origin. The populations studied include genetically based Williams syndrome (WS), behaviorally defined High Functioning Autism (HFA), and Language Impairment (LI), as well as children with Early Unilateral Focal Lesions (FL). These groups will be contrasted with typically developing (TD) controls. In addition to characterizing sociability and temperament across all groups, the study will evaluate information processing of social vs. non-social, visual, and auditory affective stimuli. Part of the research will also include examining the integrity of neural systems underlying social-affective behavior using high-resolution brain imaging. Collectively, these studies will help understanding of the interrelationships of the social and affective components of communication and their underpinnings, which may contribute to better-informed treatment methods in the future.