Contrasting, a vocabulary learning strategy in which new words are presented with form-similar words, has previously been shown to lead to a desirable difficulty. This study examines the influence of such contrasting on feedback processing with the aim to elucidate the mechanisms underlying the desirable difficulty effect observed in word learning. We manipulated the orthographic similarity between the answer options in a multiple-choice vocabulary learning task to create easy (no contrasting) and difficult (contrasting) conditions, and measured feedback-locked ERP components known as the Feedback-Related Negativity (FRN), Fronto-Central Positivity (FCP), and P300 during six subsequent rounds of learning. The data replicate previously observed behavioural patterns for the difficult contrasting condition, showing higher error rates during learning, but higher retention rates in post-tests. The ERP data point to subtle effects of the difficulty manipulation on the FCP and P300 components. These findings are interpreted in the context of previous feedback processing studies.
