Recognizing the unconscious.

Recognition memory enables us to discriminate whether an event has occurred in the past, and is widely interpreted to reflect the conscious retrieval of episodic traces or familiarity. Non-conscious mnemonic influences, such as repetition priming, are thought to have a negligible effect on standard tests of recognition memory. A major difficulty with this conclusion is that it is exclusively based on the results from experimental protocols that use stimulus materials available to conscious perception. In eight experiments (N = 144), we tested the necessity of mechanisms related to conscious perception for accurate recognition memory by manipulating observers' awareness of either the encoded event and/or the retrieval cues. Remarkably, observers made accurate objective and subjective recognition memory-guided judgments without visual awareness of the encoded events, retrieval cues or, most strikingly, both. These results demonstrate that non-conscious processes can drive accurate recognition memory, and are a significant challenge to neurobiological accounts centered on the conscious retrieval of episodic traces or familiarity.