Dissociating the Impact of Memorability on Electrophysiological Correlates of Memory Encoding Success.

Despite its unlimited capacity, not all visual information we encounter is encoded into visual long-term memory. Traditionally, variability in encoding success has been ascribed to variability in the types and efficacy of an individual's cognitive processes during encoding. Accordingly, past studies have identified several neural correlates of variability in encoding success, namely, frontal positivity, occipital alpha amplitude, and frontal theta amplitude, by contrasting the electrophysiological signals recorded during successful and failed encoding processes (i.e., subsequent memory). However, recent research demonstrated individuals remember and forget consistent sets of stimuli, thereby elucidating stimulus-intrinsic factors (i.e., memorability) that determine the ease of memory encoding independent of individual-specific variability in encoding processes. The existence of memorability raises the possibility that canonical EEG correlates of subsequent memory may reflect variability in stimulus-intrinsic factors rather than individual-specific encoding processes. To test this, we recorded the EEG correlates of subsequent memory while participants encoded 600 images of real-world objects and assessed the unique contribution of individual-specific and stimulus-intrinsic factors on each EEG correlate. Here, we found that frontal theta amplitude and occipital alpha amplitude were only influenced by individual-specific encoding success, whereas frontal positivity was influenced by stimulus-intrinsic and individual-specific encoding success. Overall, our results offer novel interpretations of canonical EEG correlates of subsequent memory by demonstrating a dissociable impact of stimulus-intrinsic and individual-specific factors of memory encoding success.

Working Memory Content Is Distorted by Its Use in Perceptual Comparisons.

Visual information around us is rarely static. To perform a task in such a dynamic environment, we often have to compare current visual input with our working memory (WM) representation of the immediate past. However, little is known about what happens to a WM representation when it is compared with perceptual input. To test this, we asked young adults (N = 170 total in three experiments) to compare a new visual input with a WM representation prior to reporting the WM representation. We found that the perceptual comparison biased the WM report, especially when the input was subjectively similar to the WM representation. Furthermore, using computational modeling and individual-differences analyses, we found that this similarity-induced memory bias was driven by representational integration, rather than incidental confusion, between the WM representation and subjectively similar input. Together, our findings highlight a novel source of WM distortion and suggest a general mechanism that determines how WM interacts with new visual input.

On our susceptibility to external memory store manipulation: examining the influence of perceived reliability and expected access to an external store.

Offloading memory to external stores (e.g., a saved file) allows us to evade the limitations of our internal memory. One cost of this strategy is that the external memory store used may be accessible to others and, thus, may be manipulated. Here we examine how reducing the perceived reliability of an external memory store and manipulating one's expectation for future access to such a store can influence participants' susceptibility to its manipulation (i.e., endorsing manipulated information as authentic). Across three pre-registered experiments, participants were able to store to-be-remembered information in an external store. On a critical trial, we surreptitiously manipulated the information in that store. Results demonstrated that an explicit notification of a previous manipulation of that store and the warning that the store will be inaccessible in the future can decrease susceptibility to manipulation of that store. Results are discussed in the context of the metacognitive monitoring and control of memory reports in situations that involve the distribution of memory demands across both internal and external spaces.