Keele Research Repository

The current thesis provides novel insights into the n–2 repetition cost, a task-switching behavioural effect thought to reflect cognitive inhibition. The n–2 repetition cost is widely used as a measure of group and individual differences in inhibitory control; however, there was uncertainty around its reliability and the extent to which it reflects cognitive inhibition. Overall, the current thesis indicates that the n–2 repetition cost is unlikely to be a measure of cognitive inhibition. Experiment 1 showed that the n–2 repetition cost has low reliability at an individual level, which questions its use as a measure of individual differences in inhibitory control. Experiments 2–4 demonstrated that the n–2 repetition cost is considerably modulated by a non-inhibitory mechanism (i.e., episodic retrieval), which means that the common understanding that the cost reflects cognitive inhibition is incomplete. Furthermore, Experiments 5–7 show that the n–2 repetition cost seems not affected by cognitive resources as it is not modulated by working memory load; however, from Experiments 8–9 it cannot be said for certain that the cost is not modulated by attentional resources, because a trend for the cost to be smaller under conditions exhausting attentional resources was present. In terms of the individual differences in the n–2 repetition cost, this thesis shows that they are not explained with processing speed, depressive rumination, working memory capacity, or day-to-day distractibility trait (Experiments 1, 4, 7, 8–9). And, computational modelling analyses (ex-Gaussian and diffusion modelling; Simulation Studies 1–4) support the view that the n–2 repetition cost is mainly due to non-inhibitory mechanisms. Taken together, the current thesis indicates that the n–2 repetition cost is unlikely to reflect cognitive inhibition, and if used as such should be interpreted with caution.