Approachability and the amygdala: insights from Williams syndrome.

Williams syndrome (WS) is a genetic neurodevelopmental disorder in which hypersociability is a characteristic feature. Given that the amygdala has been identified as an integral component of the neural system underlying sociability, researchers have suggested that the abnormal amygdala volumes found in individuals with WS may play a role in their hypersociability. The aim of this study was to examine the relationship between amygdala volume and hypersociability, as measured by approachability ratings, in 22 individuals with WS and 22 normal controls matched on chronological age, sex, and handedness. We confirmed previous findings of increased amygdala volumes and higher approachability ratings of both 'positive' and 'negative' faces in individuals with WS. A positive relationship between right amygdala volume and approachability ratings was found in individuals with WS, particularly ratings of 'negative' faces. The results unexpectedly revealed that individuals with WS report using features other than the eyes and mouth to determine approachability, particularly when they are younger. These findings support the theory that amygdala dysfunction in WS is related to their hypersociability. Furthermore, we propose that individuals with WS use atypical cognitive strategies compared to controls to determine approachability.