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

Abstract

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.

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“…2d and Table S2). Our findings coincided with the theory of a privileged WM state of faces that showed improved accuracy and response time compared to non-faces (Brady et al, 2019;Lin et al, 2019). These findings suggest a differential cognitive state and distinct neural representations for the short-term memory of faces, possibly through the top-down modulation from prefrontal and parietal regions.…”

Is working memory inherently more “precise” than long-term memory? Extremely high fidelity visual long-term memories for frequently encountered objects.

“…For example, it is known that interference between items in visual long-term memory is based on semantic similarities rather than perceptual overlap (Konkle, Brady, Alvarez, & Oliva, 2010), and that items interfere with each other within a category-based structure in visual memory (e.g., Maxcey, Glenn, & Stansberry, 2018). Understanding the meaning of a stimulus is also critical to successful encoding into visual long-term memory, as items that are understood are better remembered than identical visual stimuli that are not understood by participants (e.g., Brady, Alvarez, & Störmer, 2019; Wiseman & Neisser, 1974). Thus, there are many reasons to suspect that there could be a fundamental difference between working memory and long-term memory in the degree of perceptual detail that can be stored and the tendency to rely on conceptual structure rather than perceptual information.…”

Human faces and face‐like stimuli are more memorable

“…Three previous studies (Brady et al, 2019;Dubey et al, 2015;Maguire et al, 2001) have examined memorability for somewhat similar types of stimuli to ours with a different approach and methodology. Maguire et al (2001) examined memory for buildings, human faces, and animal faces, and Brady et al (2019) compared memorability for stimuli that had different grades of resemblance to faces (from non-faces to unambiguous faces). These previous studies, in addition to using only black and white stimuli (unlike our stimuli, most of which were colored) and analyzing a smaller number of images, also presented them for durations that differ from ours, significantly so in the work of Maguire et al (at 3000 ms) and less so in the work of Brady et al (at 500 ms).…”

“…In fact, our results show that there is a gradient in which the more an image looks like a real human face, the more memorable it is (see Figure 2). Three previous studies (Brady et al, 2019;Dubey et al, 2015;Maguire et al, 2001) have examined memorability for somewhat similar types of stimuli to ours with a different approach and methodology. Maguire et al (2001) examined memory for buildings, human faces, and animal faces, and Brady et al (2019) compared memorability for stimuli that had different grades of resemblance to faces (from non-faces to unambiguous faces).…”