A psychological study of the personalities of XYY- and XXY-men
Theilgaard A.
Acta Psychiatr Scand Suppl. 1984;315:1-133.


This psychological study of the personalities of XYY- and XXY-men is part of a multidisciplinary investigation of non-institutionalized males with sex chromosome aberrations. Past and present views on these conditions have presented contradictory statements reflecting the enthusiasm with which abnormalities have been sought and recorded in studies of newly discovered conditions - not always with due respect to the validity of the methods applied. Methodological flaws include sampling bias, generalizations unacceptably made on single cases, lack of control groups, lack of a blind evaluation procedure and finally lack of sufficient broad-spectred data. Thus an impetus to reassessment of the sex aneuploid groups presents itself. Though four hypotheses have been set forth, it has not necessarily been in search of one universally appropriate theory. In matters as complicated as these concerning interrelations of biological, psychological and social factors, it does not enhance scientific thinking to try to make straight-line cause-and-effect connections; it is important to attack the question from different perspectives, and one theory does not make another redundant. This procedure has not elicited a cacophony of ideas from so many diverse sources, that it is difficult to distinguish the nature of the issues, which are under discussion. On the contrary, in the attempt to examine the four hypotheses a picture has emerged: This does not show any inconsistencies or controversies regardless of the perspective from which it is seen - thus manifesting the force of inner coherence. The first hypothesis deals with the question whether or not distinctive XYY- and XXY-syndromes of psychological features exist. The comparisons of the total amount of data stemming from the XYY-men and the XXY-men lead to the statement, that the two groups are more alike than different. Both groups show a slight general deficit in global intelligence, but a wide spectrum of IQ scores is possible in both conditions. There is no evidence of different cognitive styles. Regarding personality both sex aneuploid groups seem to have more than less characteristics in common. There is a slight difference concerning the defensive pattern; the XYY's seem more rigid in their thinking, the XXY's being more indecisive. The latter group tends to be more submissive and dependent than the former, they are inclined to show less aggression against others, and criminal acts committed by XXY's point to be less impulsive than in the case of XYY's. The diversities manifesting themselves belong mainly to the sexual domain: the gender role and the sexual behaviour
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