Birth order, birth interval, and deviant sexual preferences among sex offenders.

Abstract

We investigated whether birth order and birth interval are associated with phallometric responding among 168 sex offenders. Based on the immunoreactivity hypothesis, we predicted that a larger number of older brothers and a shorter birth interval between the offenders and their next older brothers would be associated with more deviant responding. Results showed that a larger number of older brothers (but not older sisters, younger brothers, or younger sisters) was associated with more deviant responding on the Most Deviant Index, a general measure of sexual deviance. A larger number of older brothers was associated with arousal to nonsexual violence against women and children, but contrary to expectation, the same association was also found for the number of younger brothers. A short birth interval with the next older brother was associated with greater relative arousal to nonsexual violence, but the correlation with the Most Deviant Index did not reach statistical significance. Overall, results were consistent with the main predictions, but the effects of birth order and birth interval were mostly restricted to arousal to nonsexual violence. Birth order and birth interval were not associated with pedophilic interests or gender preferences.