The Role of Meaning in Visual Memory: Face-Selective Brain Activity Predicts Memory for Ambiguous Face Stimuli

How people process images is known to affect memory for those images, but these effects have typically been studied using explicit task instructions to vary encoding. Here, we investigate the effects of intrinsic variation in processing on subsequent memory, testing whether recognizing an ambiguous stimulus as meaningful (as a face vs as shape blobs) predicts subsequent visual memory even when matching the perceptual features and the encoding strategy between subsequently remembered and subsequently forgotten items. We show in adult humans of either sex that single trial EEG activity can predict whether participants will subsequently remember an ambiguous Mooney face image (e.g., an image that will sometimes be seen as a face and sometimes not be seen as a face). In addition, we show that a classifier trained only to discriminate between whether participants perceive a face versus non-face can generalize to predict whether an ambiguous image is subsequently remembered. Furthermore, when we examine the N170, an event-related potential index of face processing, we find that images that elicit larger N170s are more likely to be remembered than those that elicit smaller N170s, even when the exact same image elicited larger or smaller N170s across participants. Thus, images processed as meaningful, in this case as a face, during encoding are better remembered than identical images that are not processed as a face. This provides strong evidence that understanding the meaning of a stimulus during encoding plays a critical role in visual memory.