Recent studies indicate that intentionally suppressing the retrieval of an unwanted memory can impair its later recall. However, it is not clear how long this intentional suppression effect persists. The aim of the current study was to investigate this question using a Think/No-Think paradigm. After participants studied pairs of unrelated words, the cue words from each pair were presented either 0, 4, or 12 times during the Think/No-Think phase of the experiment. Participants were asked to either avoid thinking of the word associated with the cue (Supression condition) or to recall it (Response condition). Participants were then asked to recall the cued words immediately and after a delay of 24 hours. Recall performance in the 12-cue No-Think condition was worse than in the baseline (0) condition, both immediately and 24 hours later. Moreover, the participants who thought about something other than the target during the No-Think trials showed poorer recall than those who did not do so. These results suggest that the effect of intentional suppression that occurs under conditions of self-initiated thought substitution can last for over 24 hours.

Key words. intentional suppression, long-term forgetting, self-initiated thought substitution