Hypersociability in Williams syndrome

Studies of abnormal populations provide a rare opportunity for examining re lationships between cognition, genotype and brain neurobiology, permitting comparisons across these different levels of analysis. In our studies, we i nvestigate individuals with a rare, genetically based disorder called Willi ams syndrome (WMS) to draw links among these levels. A critical component o f such a cross-domain undertaking is the clear delineation of the phenotype of the disorder in question. Of special interest in this paper is a relati vely unexplored unusual social phenotype in WMS that includes an overfriend ly and engaging personality. Four studies measuring distinct aspects of hyp ersocial behavior in WMS are presented, each probing specific aspects in WM S infants, toddlers, school age children, and adults. The abnormal profile of excessively social behavior represents an important component of the phe notype that may distinguish WMS from other developmental disorders. Further more, the studies show that the profile is observed across a wide range of ages, and emerges consistently across multiple experimental paradigms. Thes e studies of hypersocial behavior in WMS promise to provide the ground-work for crossdisciplinary analyses of gene-brain-behavior relationships.