Can People Really Suppress Unwanted Thoughts? On optimal test conditions and authorship effects in the Think/No-Think (TNT) Task

Whether people can actively suppress unwanted thoughts is highly controversial. Anderson and Green (2001) developed the Think/No-Think (TNT) task and found that suppressing a memory reduces later recall, referred to as the Suppression-Induced Forgetting (SIF) effect. While some studies replicate this effect, others do not. To better understand the factors influencing the SIF effect, we developed two TNT methodological quality checklists (a 12-item essential version and an extensive 25-item version) based on optimal test conditions proposed by Nardo and Anderson (2024). We then assessed whether following these optimal test conditions predicted SIF effects across 100 TNT studies (143 effects) conducted with non-clinical samples. We found that methodological quality significantly predicted SIF effect significance for the 25-item checklist, but not robustly for the 12-item checklist. Methodological quality did not predict the magnitude of the reported SIF effect. Because there remains considerable uncertainty on the optimal TNT test conditions, we recommend authors report their methods, using the checklists provided in this paper. Exploratory analyses further suggested that studies involving original TNT developer reported significant SIF effects more frequently (95%) than studies without developer involvement (68%). This authorship effect remained significant after controlling for higher methodological quality. More independent studies are thus needed to mitigate possible biases.