Psychological Characteristics Associated with XYY Sex-Chromosome Complement in a State Mental Hospital

Abstract

A group of males with XYY sex-chromosome complement was compared with a matched group of fellow-patients in a state mental hospital. There were very few significant differences between mean scores of the two groups on psychological tests. There were, however, differences in the inter-relations of tests. There was a marked discrepancy between the two groups in the effect of response set (defensiveness) on replies to questionnaires. A difference in the structure of aggression or hostility was also detected. If response set is indeed an important determinant of psychological test scores, and if its mode of action differs in XYY patients and in comparable non-XYY patients, then any obtained mean differences (or similarities) are suspect. The importance of this caveat becomes even more evident when we consider that the unco-operative patients who had to be omitted from the testing were probably high defenders. Perhaps the most direct approach to eliciting the psychological peculiarities of XYY patients would be to find out what it is that the high defenders among them do not wish to admit. The patient's and the psychologist's perceptions of the purpose of a particular test item are often quite disparate. The next stage of the enquiry is to ask what the patient thought he would be admitting if in fact he had not exercised defensiveness in a particular response.