Multiple processes underlying dimensional change card sort performance: a developmental electrophysiological investigation.

Cognitive flexibility follows a protracted developmental trajectory [Morton, J. B. Understanding genetic, neurophysiological, and experiential influences on the development of executive functioning: The need for developmental models. Wiley Interdisciplinary Reviews: Cognitive Science, 2010]. For example, performance and patterns of brain activity associated with the dimensional change card sort (DCCS) show continued age-related changes into early adolescence. According to many theoretical accounts, the DCCS places demands on a single underlying executive process. In the present study, we investigated the possibility that multiple processes unfold within the timeframe of a single DCCS trial through the use of ERPs. Children (n = 40), adolescents (n = 20), and adults (n = 20) performed a modified version of the DCCS with distinct instruction cue- and stimulus-related periods. On any particular trial, the sorting rule either changed (i.e., switch trials) or remained the same (i.e., repeat trials), and the imperative stimulus either embodied conflict (i.e., bivalent stimuli) or did not (i.e., univalent stimuli). Findings were consistent with the hypothesis that multiple distinct executive processes unfold within a single trial. First, for all age groups, rule switching and conflict processing made additive contributions to variability in RT. Second, ERPs time-locked to the instruction cue revealed a late frontal negativity whose amplitude was greater for switch trials relative to repeat trials and that was associated with the magnitude of the behavioral switch cost, whereas ERPs time-locked to the imperative stimulus revealed a fronto-central N2 whose amplitude was greater for bivalent than univalent stimuli and that was associated with the magnitude of the behavioral conflict cost. Finally, switch and conflict-related processes showed distinct developmental trajectories. Taken together, the findings suggest that multiple executive processes underlie DCCS performance and its development. Theoretical implications are discussed.