Time course of colour-word contingency learning: Practice curves, pre-exposure benefits, unlearning, and relearning

In performance-based measures of implicit contingency learning, learning effects have been observed very early in the task (e.g., within a few trials) and remain stable throughout the experiment. This has been taken to suggest that the contingency knowledge underlying the learning effects is formed almost instantly and does not develop further across trials. One potential concern with the available evidence is that response times are overall much slower early on in an experiment and speed up over practice in a decelerating function. If learning effects scale with overall response time, then learning effects observed early on in an experiment might be artificially inflated. In the current report with the colour-word contingency learning paradigm, participants were given an extended practice phase before introducing predictive stimuli (words). Thus, learning could be assessed after the large practice speedup in performance had already occurred. In one experiment, the contingency learning effect was found to again be fairly stable, but with a hint of an increasing effect with time. In a second experiment, words were pre-exposed in a neutral hue before being coloured. This increased the magnitude of the learning effect, suggesting a preparation time benefit. More importantly, the contingency learning effect was observed to increase over time. In a third experiment, we assessed unlearning rates when the contingency was removed, and relearning when the contingencies were reintroduced. The results revealed a cumulative effect of contingencies acquired across multiple blocks. In sum, the evidence reported in this paper shows that, contrary to previous claims, implicit contingency learning is cumulative.