Recognition and rejection each induce forgetting.

Recognition-induced forgetting, whereby the recognition of targeted memories induces the forgetting of related memories, results from the recognition of old objects and rejection of new objects. Here we asked whether both these tasks are necessary to induce forgetting. Our unique design allowed us to isolate the recognition of old objects from the rejection of new objects by presenting subjects with only new objects, only old objects, and a mixture of both in separate conditions of an old-new recognition task. In all three conditions, we successfully induced forgetting. The magnitude of forgetting was statistically indistinguishable across all three conditions, showing that recognition of old objects and rejection of new objects are each building blocks of forgetting. These findings pinpoint both recognition and rejection as mechanisms underlying recognition-induced forgetting and demonstrate the ubiquity of this forgetting effect.