Intentional forgetting in dysphoria: investigating the inhibitory effects of thought substitution using independent cues

Background Individuals with clinical and subclinical depression (dysphoria) exhibit problems intentionally forgetting unwanted memories on the think/no-think (TNT) paradigm (Anderson & Green, 2001). However, providing substitute words to think about instead of the to-be-forgotten targets can improve forgetting in depressed patients. Objectives To determine if thought substitution can enhance forgetting in dysphoric participants and to examine the potential mechanisms (blocking or inhibition) that might underpin successful forgetting. Methods Thirty-six dysphoric and 36 non-dysphoric participants learned neutral word-pairs and then practiced responding with the targets to some cues (think trials) and suppressing responses to others (no think trials). Half the participants were provided with substitute words to recall instead of the original targets (aided suppression) and half were simply told to avoid thinking about the targets (unaided suppression). Finally, participants completed two recall tests for the targets; one cued with the original probes and one with independent probes. Results Regardless of suppression condition (aided or unaided), dysphoric participants exhibited impaired forgetting, relative to their non-dysphoric counterparts, but only when cued with the original probes. Furthermore, higher depression scores were associated with poorer forgetting. In the aided condition, successful forgetting was observed on both the original and independent probe tasks, which supports the inhibitory account of thought substitution. Limitations Non-clinical status of the dysphoric participants was not confirmed using a validated measure. Conclusions Findings do not support the utility of thought substitution as a method of improving the forgetting in depressed participants, but do support the inhibition account of thought substitution.