XYY Individuals in a Special School

¹ Consultant Clinical Psychologist, Ladysbridge Hospital, Banff, AB4 2JS; and Clinical Senior Lecturer in Mental Health, University of Aberdeen
² Consultant Physician, Aberdeen Royal Infirmary, Foresterhill, Aberdeen, AB9 2ZB; and Clinical Senior Lecturer in Medicine and Genetics, University of Aberdeen

Data on five XYY subjects from a special school setting are reported as adding to the sum of information available. With increasing evidence, it is becoming more likely that further XYY subjects will be found in normal as well as institutional or `mental-penal' situations, and that there is an even greater likelihood of finding such individuals among dull intelligence, borderline and retarded populations. This does not exclude the possibility of XYY subjects of average or above average intelligence, but would confirm the presence of a positively skewed distribution of intelligence in XYY persons.

Quantitatively, it is clear that the five subjects reported here are of borderline or feeble-minded intellectual level, with a mean IQ around two standard deviations below the general population mean. There is some evidence of a tendency toward performance rather than verbal dominance in cognitive skills, but at the same time evidence of motor carelessness and impulsivity. Social maturity is also subnormal.