Intentional Forgetting Needs Intentional Remembering

Episodic memories may become suppressed, both incidentally and intentionally. Incidental suppression is a result of a competition induced by interfering items or responses. In contrast, intentional suppression is said to result from conscious attempts to suppress certain memory items, and should thus not depend on competition induced by interfering items or responses. However, intentional suppression is typically engendered using the Think/No-Think paradigm, in which participants are required to retrieve some target items and to suppress others. Therefore, rather than intentional suppression, forgetting in this paradigm may reflect incidental suppression of No-Think items induced by interference via prior retrieval of the Think items. To distinguish between these possibilities, we tested participants (n = 40) using an adjusted suppression paradigm, which did not include the Think condition (ExcludeThink paradigm) and compared it with the standard suppression paradigm (IncludeThink paradigm; n = 39) which included a think condition. We found that suppression was not observed in the ExcludeThink paradigm, but only in the IncludeThink paradigm. These results indicate that interference via prior retrieval is necessary to induce forgetting.