The Number of Encoding Opportunities, but not Encoded Representations in Visual Working Memory Determines Successful Encoding into Visual Long-Term Memory

Abstract

Visual long-term memory (VLTM) allows us to store a virtually unlimited amount of visual information (e.g., Brady et al., 2008). Despite its unlimited capacity, not all visual information gets encoded into VLTM. One robust way to improve VLTM encoding is to restudy the visual information. However, the exact mechanism underlying this restudy benefit is not clear. In a series of four experiments, we examined following three hypotheses. First, the restudy benefit stems from the increase in the number of visual working memory (VWM) representations encoded as the visual information is restudied. Second, instead of the increase in the number of VWM representations, the restudy benefit stems from the increase in the total number of encoding opportunities. Lastly, the encoding benefit stems from successful recognition of the encoded information when it is restudied. To dissociate the number of encoded VWM representations from the number of encoding opportunities, we presented varying numbers of copies of the same visual information at each restudy opportunity. To measure the number of VWM representation encoded at each restudying opportunity, we utilized two previously-established EEG correlates of VWM representations, namely the posterior alpha power suppression and the posterior sustained negativity (Fukuda, Mance, & Vogel, 2015). Here, we found that 1) it is the number of encoding opportunities, rather than the number of encoded VWM representations, that leads to the restudy benefit and that 2) successful retrieval during restudying augments VLTM encoding in addition to the effect of the number of encoding opportunities. Taken together, our results specify the nature of visual working memory’s contribution to VLTM encoding.