Investigating intentional forgetting using pupillometry: no evidence for the ongoing allocation of cognitive resources during forgetting

The ability to intentionally forget presented information is explained mainly by two theoretical accounts. The inhibitory control account states that forgetting is an active process, because to-be-forgotten items are inhibited. The selective rehearsal account emphasises working memory processes acting on the to-be-remembered items to aid later retrieval. Accordingly, to-be-forgotten items are dropped from working memory, because they are no longer processed. As pupil size is a reliable measure of cognitive resource allocation, we used this measure to differentiate between both theoretical accounts. Two experiments applying nonparametric statistical analyses revealed that pupils dilated most during encoding when the task required remembering. Experiment 2 revealed that participants were partly aware of the control they had over remembering and forgetting. The results of both experiments are better explained by the selective rehearsal account than by inhibitory control. Potential reasons for the occurrence of the diverging theoretical explanations of directed forgetting are discussed.