Executive functions and delay aversion in preschool hyperactive children

Abstract

The traditional view of attention-deficit hyperactivity disorder (AD/HD) as an executive dysfunction (EDF) disorder underpinned by a failure of the inhibition system (Barkley, 1997) is to some extent challenged by evidence that suggests EF deficits are context-dependent. In seeking to address this issue Somuga-Barke has proposed an alternative model that implicates delay aversion (DA) as the core feature of AD/HD. The aim of this thesis was to explore the relationship between AD/HD, EF and DA in a preschool population where maturation is less likely to obscure relationships between early emerging skills. Before this was possible it was necessary to examine normal task performance in the preschool years. Therefore, this thesis contains two studies. The first explored the properties of the task measures and age-related changes in task performance. The second examined the role of hyperactivity in task performance.

In the first study preschool children (N=60) were tested on a range of EF and delay measures. Age-related changes in task performance were explored using multivariate statistical procedures. Age-related increments in task performance were observed for EF, but not delay, tasks. The findings also suggested preschool EFs are similar in structure to that found in school-age children (i.e., are fractionated).

In the second the modified task battery was applied to preschool children (N=157). Within this community sample hyperactive symptoms were assessed using both rating scales and a clinical interview. The relationship between hyperactivity, EP and DA was explored using both median split and clinical cutoffs on the behavioural measures. Results indicated that hyperactivity is associated with delay task performance. This association was evident for both males and females at age 3 and age 5, and was independent of IQ and conduct problems. This robust finding supported the DA hypothesis. In contrast, hyperactivity was not associated with EF performance, but was associated with disinhibition at age 5 years. This finding offered only partial support for the EDF model.

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