Further delineation of the executive deficit in males with fragile-X syndrome

This paper presents a detailed analysis of one aspect of performance by young males with fragile-X syndrome (FMR-1 full mutation) who were assessed on a computerised visual search task as part of a larger study examining aspects of attention [Neuropsychologia 38 (2000) 1261]. They were matched on chronological and mental age to 25 boys with Down's syndrome (trisomy 2 1) and on mental age to 50 mainstream school boys (controls). The controls were further divided into those matched on "poor attention" to the fragile-X boys and a "good" attention group, as rated by the comprehensive teacher rating scale (ACTeRS) questionnaire. Both fragile-X and Down's syndrome boys made significantly more repeated responses on targets (but a lower proportion of errors based on confusion of shape) than the two control groups and these differences were stronger in the fragile-X group. In the single target condition, search was for a single type of target throughout. In the dual target condition, participants were required to alternate between two different targets. Fragile-X boys showed significantly greater inability than Down's syndrome and normal boys to switch attention between targets and both learning-disabled groups were inferior to the control groups. Thus, both learning-disabled groups displayed a weakness in inhibiting repetition and in switching attention from one type of target to another and the impairments were more acute in fragile-X boys. The results provide further support for an attention deficit in this population at higher levels of attention control/executive functioning that involve switching visual attention and inhibiting repetitious behaviour. (C) 2002 Elsevier Science Ltd. All rights reserved.