The cognitive effort explanations of contextual interference (CI) and implicit motor learning represent a paradox in which cognitive involvement is seen to be advantageous or disadvantageous for learning. The authors aimed to resolve this paradox by measuring cognitive effort and working memory dependence during low and high CI practice on two Australian Rules Football tasks (kicking and handball). Measures of cognitive effort included: kicking and handball outcome performance during acquisition and during a test of retention, performance on a probe reaction time task during a sample of acquisition trials, and self-reported levels of cognitive effort. Measures of implicit and explicit learning included kicking and handball performance during a secondary task transfer, and self-report verbal protocols (number of verbal rules and hypotheses reported). The results suggest that high CI may cause an implicit mode of learning, perhaps due to the interference caused by task switching. However, these findings are restricted to the more complex of the 2 tasks (kicking).