Directed-Forgetting in Working Memory

How does the intent to remember or forget information affect working memory (WM)? To explore this question, in four experiments, we gauged the availability of the to-be-forgotten information directly. Participants remembered six words presented sequentially in separate frames. After each word offset, the frame turned either blue or orange, indicating a to-be-remembered or to-be-forgotten word, respectively. In all experiments, consistently poor recognition performance for to-be-forgotten words and facilitation of to-be-remembered words demonstrated that intent has a strong impact on WM. These directed-forgetting effects are remarkably robust: They can be observed when testing the to-be-forgotten words up to four times (Experiment 1, n=341), for both item and binding memory (Experiment 3, n=124), and even when information has to be maintained in WM up to 5s until the memory cue is presented (Experiment 2+4, n=302+321). Our study establishes a new method to jointly study the effects of intent on WM content for both relevant and irrelevant information and provides evidence for directed-forgetting in WM. Our research suggests that a combination of two processes cause directed-forgetting in WM: One process reduces memory strength of earlier memory representations as a function of subsequently encoded events. Another process rapidly encodes or boosts memory strength only when the person intends to remember that information.

Language Shift Effect on Memory Generalization of Chinese-English Bilinguals

Language shift occurs when people learn information in one language but recall it in another language. This mismatch between encoding and retrieval language is found to impair memory accuracy when memory is tested immediately after learning. However, does the observed language shift effect still exist after a certain period of delay? Would it influence other aspects of memory, especially memory generalization? To address these two questions, we performed a memory experiment among unbalanced Chinese-English bilinguals. In the experiment, participants were required to read two stories (one in English, one in Chinese) and to retell the stories in Chinese from their memories afterward. Delay interval was manipulated in the experiment where participants either took memory recall tests immediately after story-reading or after 24 hours' delay. To analyze memory generalization, we coded the generalized words participants used to retell the stories. The results suggest that language shift (encoding in English and retrieving in Chinese) leads to a more generalized description in a memory recall task. However, the observed language shift effect disappears after 24 hours' delay. It can be concluded that language shift impacts bilingual learners' memory generalization in immediate recall tests, but such effect disappears after 24 hours' delay, which indicates the key role of delay interval in modulating language shift effect.

Object-based selection in visual working memory

Attentional mechanisms in perception can operate over locations, features, or objects. However, people direct attention not only towards information in the external world, but also to information maintained in working memory. To what extent do perception and memory draw on similar selection properties? Here we examined whether principles of object-based attention can also hold true in visual working memory. Experiment 1 examined whether object structure guides selection independently of spatial distance. In a memory updating task, participants encoded two rectangular bars with colored ends before updating two colors during maintenance. Memory updates were faster for two equidistant colors on the same object than on different objects. Experiment 2 examined whether selection of a single object feature spreads to other features within the same object. Participants memorized two sequentially presented Gabors, and a retro-cue indicated which object and feature dimension (color or orientation) would be most relevant to the memory test. We found stronger effects of object selection than feature selection: accuracy was higher for the uncued feature in the same object than the cued feature in the other object. Together these findings demonstrate effects of object-based attention on visual working memory, at least when object-based representations are encouraged, and suggest shared attentional mechanisms across perception and memory.

A Model of Position Effects in the Sequential Lineup

What is the effect of placing the suspect in different positions in a sequential lineup? To explore this question, we developed and applied a model called the Independent Sequential Lineup model which analyzes a sequential lineup in terms of both identification position, the position at which the witness identifies a lineup item as the target, and target position, the position at which the target or suspect appears. We conducted a large-scale online eyewitness memory experiment with 7,204 participants each of whom was tested on a 6-item sequential lineup with an explicit stopping rule. The model fit these data well and revealed systematic effects of lineup position on underlying discriminability and response criteria. We also fit the model to data from a similar pair of experiments conducted recently by Wilson, Donnelly, Christenfeld and Wixted (2019; Journal of Memory and Language, 104, 108-125) both with and without application of a stopping rule. In all data sets, if a stopping rule is applied, underlying discriminability was found to be constant, or to increase slightly, across target position. In the absence of a stopping rule, discriminability was found to decrease substantially. We also observed a substantial increase in response criteria following presentation of the target. We discuss the implications of these findings for current theories of recognition memory and current applications of the sequential lineup in different jurisdictions.

Frequently Occurring Melodic Patterns are Easier to Recall

Melodic memory continues to present a paradox. Listeners excel at recognizing melodies once encoded in long term memory, but often struggle during encoding. In order to investigate this paradox, we employ a recall design to investigate melodic encoding. Here we report results from a forward, serial recall within-subjects melodic memory experiment (n = 39) using an expert population of musicians trained in moveable-do solfege in order to model melodic memory using music theoretic response categories. Compatible with theoretical frameworks predicting a processing facilitation advantage, more frequently occurring musical patterns are remembered more quickly and more accurately than less frequently occurring patterns. The evidence presented here is consistent with evidence suggesting that latent understanding of musical schemas can be modeled with musical corpora. Further, computationally derived measures related to information processing from both the Information Dynamics of Music model and FANTASTIC toolbox outperform models of melodic memory that only account for the length of the melody measured in number of notes. Results from this experiment demonstrate how expert populations can provide valuable insight into melodic memory and tonal cognition. The framework provided here also provides an empirical basis linking literature investigating melodic anticipation with melodic memory.

Scene wheels: Measuring perception and memory of real-world scenes with a continuous stimulus space

Precisely characterizing mental representations of visual experiences requires careful control of experimental stimuli. Recent work leveraging such stimulus control in continuous report paradigms have led to important insights; however, these findings are constrained to simple visual properties like colour and line orientation. There remains a critical methodological barrier to characterizing perceptual and mnemonic representations of realistic visual experiences. Here, we introduce a novel method to systematically control visual properties of natural scene stimuli. Using generative adversarial networks (GAN), a state-of-art deep learning technique for creating highly realistic synthetic images, we generated scene wheels in which continuously changing visual properties smoothly transition between meaningful realistic scenes. To validate the efficacy of scene wheels, we conducted a memory experiment in which participants reconstructed to-be-remembered scenes from the scene wheels. Reconstruction errors for these scenes resemble error distributions observed in prior studies using simple stimulus properties. Importantly, memory precision varied systematically with scene wheel radius. These findings suggest our novel approach offers a window into the mental representations of naturalistic visual experiences.

Exploring the Cognitive Load of Expert and Novice Map Users Using EEG and Eye Tracking

The main objective of this research is to explore the cognitive processes of expert and novice map users during the retrieval of map-related information, within varying difficulty levels (i.e., easy, moderate, hard), by using eye tracking and electroencephalogram (EEG). In this context, we present a spatial memory experiment consisting of a large number of stimuli to study the effect of task difficulty on map users’ behavior through cognitive load measurements. Next to the reaction time and success rate, we used fixation and saccade related eye tracking metrics (i.e., average fixation duration, the number of fixations per second, saccade amplitude and saccade velocity), and EEG power spectrum (i.e., event-related changes in alpha and theta frequency bands) to identify the cognitive load. While fixation metrics indicated no statistically significant difference between experts and novices, saccade metrics proved the otherwise. EEG power spectral density analysis, on the other side, suggested an increase in theta (i.e., event-related synchronization) and a decrease in alpha (except moderate tasks) (i.e., event-related desynchronization) at all difficulty levels of the task for both experts and novices, which is an indicator of cognitive load. Although no significant difference emerged between two groups, we found a significant difference in their overall performances when the participants were classified as good and relatively bad learners. Triangulating EEG results with the recorded eye tracking data and the qualitative analysis of focus maps indeed provided a detailed insight on the differences of the individuals’ cognitive processes during this spatial memory task.