Executive functioning by 18-24-month-old children: Effects of inhibition, working memory demands and narrative in a novel detour-reaching task

Infants can inhibit a prepotent but wrong action towards a goal in order to perform a causal means-action. It is not clear, however, whether infants can perform an arbitrary means-action while inhibiting a prepotent response. In four experiments, we explore this executive functioning in 18-24-month-old children. The working memory and inhibition demands in a novel means-end problem were systematically varied in terms of the type and combination of means-action(s) (causal or arbitrary) contained within the task, the number of means-actions (I or 2), the goal visual availability and whether the task was accompanied by a narrative. Experiments 1 and 2 showed that children performed tasks that contained causal as opposed to arbitrary information more accurately; accuracy was also higher in tasks containing only one step. Experiment 2 also demonstrated that performance in the arbitrary task improved significantly when all sources of prepotency were removed. In Experiment 3, task performance improved when the two means-actions were intelligibly linked to the task goal. Experiment 4 demonstrated that the use of a narrative that provided a meaningful (non-causal) link between the two means-actions also improved children's performance by assisting their working memory in the generation of a rationale. Findings provide an initial account of executive functioning in the months that bring the end of infancy. Copyright (c) 2006 John Wiley & Sons, Ltd.