Effects of acute exercise on directed forgetting

Background: The directed forgetting paradigm involves individuals encoding a list of words (List 1; L1) and then, prior to encoding a second list of words (List 2; L2), they are given specific instructions to either remember all the words from L1 or to try and forget these words. In this paradigm, after encoding L1, those who are given the directed forgetting (DF) instructions tend to recall more words for L2 when compared to those who were given the remember (R) instructions (DF benefit effect). Similarly, those given the DF instructions tend to recall fewer words from L1 (DF cost effect). This DF phenomenon may, in part, occur via attentional inhibitory mechanisms, or mental context-change mechanisms, which may be influenced via acute exercise. Methods: The present experiment investigates if acute exercise can facilitate DF when exercise occurs after L1 forgetting instructions. Participants (N = 97; Mage = 21 years) were randomly assigned into either acute exercise (15-min high-intensity aerobic exercise) plus DF (EX + DF), 2) DF (directed forgetting) only (DF) or 3) R (remember) only (R). A standard two list (L1 and L2) DF paradigm was employed. Results: We observed evidence of a DF cost effect, but not a DF benefit effect. For L1, although both EX + DF and DF differed from R, there was no difference between EX + DF and DF. Further, although for L2, EX + DF was different than DF, neither of these groups differed when compared to R. Conclusion: We reserve caution in suggesting that exercise had a DF effect.