social cognition in ADHD (32), emotional support seeking (33), prosocial temperament (34), maternal sensitivity (35), prosocial decision making (36) and autism (37–46). Finally, variation in OXTR has been associated with the functioning (34) as well as the size of the amygdala (47, 48). Although these previous studies are valuable for the general understanding of the influences of OT and OTR on social behavior in humans, studies specifically investigating the extent to which OT and its receptor are implicated in pair-bonding behavior are warranted. We have previously reported an association between variation in the vasopressin receptor 1a gene and pair-bonding behavior in men (49), possibly analogous to how variation in this gene correlates with affiliative behavior in male voles. The aim of this study was to investigate whether variation in OXTR is associated with social functioning in general and pair-bonding in particular amongst humans. Considering the sexually dimorphic effects of OT shown in voles, our prime focus was on women.
