Brothers, sisters and antisocial behaviour

The brothers of 73 delinquent boys were found themselves to be more antisocial than the brothers of 73 matched control boys. Further, the average antisocial score of the probands' brothers increased with the number of brothers in the family, holding the number of sisters constant, and decreased with the number of sisters, holding the number of brothers constant. These results are interpreted in terms of male potentiation and female suppression of antisocial behaviour in boys. Results are also reported for 59 pairs of matched delinquent and control girls and their siblings.