Unfamiliar faces in recognition memory: spaced learning enhances subsequent recognition memory by reducing repetition priming.

Although the spacing effect is one of most robust effects in learning, its cognitive and neural mechanisms are still under investigation. Whether the spacing effect is achieved by reducing neural repetition priming or depends on learning experience is still unclear. In this event-related potential study, participants were asked to memorize 140 novel faces, half under the massed learning condition and the other half under the spaced learning condition. The afterwards recognition tests indicated that participants recognized more items under the spaced learning condition than under the massed learning condition. The electroencephalography data suggested that spaced learning was associated with a reduced familiarity effect in frontal N400. Remembered faces showed smaller repetition priming than forgotten faces under both learning conditions and spaced learning significantly reduced repetition suppression. Although no direct association was found between repetition priming and episodic memory, the difference in quantity between spaced learning and massed learning in the repetition priming can predict the different quantities in the recognition memory. These results suggest that the neural mechanism of the spacing effect is influenced by experience; however, the impact is mainly repetition priming and the spacing effect is still very robust.