Towards a model of working memory capacity and executive functions in preschoolers

The structure of executive functions in preschoolers is controversial. Miyake et al (2000) found that, in adults, inhibition, updating, and shifting are correlated but distinguishable processes; Lehto et al (2003) replicated their results with school children. Based on school children data, Im-Bolter et al (2006) proposed a four-component neo-Piagetian model, where M capacity and inhibition are basic resources, whereas shifting and updating are executive processes that partly rely on those resources. Studies on preschoolers propose a single factor (Wiebe, 2011) or two factors, often distinguishing inhibition from working memory (Miller et al, 2012). We administered three WM capacity tasks (Mr.Cucumber, Direction Following Task, and Backward Word Span), two inhibition tasks (Bear/Dragon and Day-Night Stroop), a shifting task (Dimensional Change Card Sort) and a novel Updating task to 118 children, 36 to 73 months old. The best fitting model included two highly correlated factors – one loading the capacity measures, the other loading the inhibition, shifting, and updating measures. Splitting the sample in two age groups, a single factor fit best the youngest children’s data, and two factors emerged in older children. Performance in inhibition, shifting, and updating tasks showed qualitative changes with increasing capacity; this could account for the correlation between the two factors. In preschoolers, shifting and updating seem to emerge tied to inhibition – but only when sufficient WM capacity maturation enables children to perform executive control tasks. This seems consistent with proposals of a single factor in younger children, and with Im-Bolter’s neo-Piagetian approach that posits two basic resources.