Abstract
Social cognitive competence appears to be a good predictor of social behaviour and adaptation. Individual variance in social cognitive competence is, for a substantial part, attributable to genetic factors. Deficits in social behaviour are seen in populations such as those with autism-spectrum disorders, and although social (dys)functioning may be similar at the level of behavioural phenotypes, it may substantially differ with regard to the underlying cognitive and genetic pathways. In this review study it is argued that there is a need to study the neurocognitive and behavioural phenotypes in more homogeneous genetic groups. This enables us to identify aetiological pathways to psychopathology. In both Turner syndrome (45, XO) and Klinefelter syndrome (47, XXY), basic social-cue processing deficits are observed, which may contribute to difficulties in social intuition and hence in coping with social situations. The study of these two syndromes opens up opportunities to study the influence of the X chromosome on brain behaviour developmental trajectories of social functioning and psychopathology in heterogeneous populations.

The authors have presented at AXYS Families’ Conferences and participated in AXYS Scientific Conferences.