Memory performance can be improved by retrospectively cueing an item maintained in visual working memory (VWM). Different hypotheses have been proposed to explain the mechanisms behind retro-cueing and VWM. Previous behavioral studies suggest that different retro-cue validities may lead individuals to implement retro-cues in different ways to obtain a retro-cue effect. However, there is still no clear electroencephalogram (EEG) evidence to support that the retro-cue effect under different validity conditions is triggered by different mechanisms. Herein, we investigated whether retro-cue validity modulated the mechanisms underlying the retro-cue effect in VWM by using EEGs. We manipulated retro-cue validity by using blocks in a color change detection task. Contralateral delay activity (CDA) and lateralized alpha power were used assess spatial attention and memory storage, respectively. Significant retro-cue effects were observed under both high- and low-validity conditions. More importantly, although the retro-cue could redirect spatial attention under both high- and low-validity conditions, we found that participants maintained the non-cued items during a measured time interval under the low-validity condition, but dropped them out of VWM under the high-validity condition. Our results resolve previous contradictory findings. The retro-cue effect in our study can be explained by the removal hypothesis, prioritization hypothesis, and protection-during-retrieval hypothesis. This work suggests that the mechanisms underlying the retro-cue effect are not mutually exclusive, but determined by the cue validity. Individuals can voluntarily choose different mechanisms based on the expected retro-cue validity.
Previous studies have associated visual working memory (VWM) capacity with the ability to use internal attention. Internal attention’s effect on VWM has been studied mostly using object-based retro-cues, which can direct internal attention to particular objects. In addition, by using dimension-based retro-cues recent studies have found that directing internal attention to a feature dimension in VWM can improve memory recall performance. An object-based cue can direct attention to one or several objects of the memory array, while a dimension-based cue can direct attention to one visual dimension (e.g., color or orientation) of all memory items. Many studies show that retro-cues can improve VWM performance (i.e., retro-cue benefit, RCB). Although the mechanism of object-based retro-cues has been studied for over ten years, no study to date has investigated the relationship between VWM capacity and the benefits of dimension-based retro-cues. The present study aims to explore individual differences in VWM capacity and their relationship with the use of dimension- and object-based retro-cues. We first measured participants’ VWM capacity and then asked them to conduct a dimension-based cue task and an object-based cue task. In the cue taks, we used the offset index to quantify participants’ VWM performance, and we used the RCB index to quantify the magnitude of the benefits obtained from retro-cues. We found that performed better than low-VWM-capacity participants in both dimension- and object-based cue tasks. In addition, although we identified certain RCBs obtained from both dimension- and object-based cues, we did not find any significant correlation between individual VWM capacity differences and the magnitude of the RCB obtained from object- or dimension-based cues. These results suggest that VWM capacity is not related to RCBs’ magnitude, and thus VWM storage and the use of internal attention are independent mechanisms. Moreover, we found that the participants who benefitted the most from object-based retro-cues also benefitted the most from dimension-based retro-cues in color reports; ; however, this pattern was not found in the orientation report trials. This finding suggests a partly overlapping mechanism between the use of the two retro-cue types. The present study provides the first evidence of the relationship between VWM capacity and the dimension-based internal attention process.
Visual attention and visual working memory (VWM) are two major cognitive functions for humans, and they have much in common. A growing body of research has investigated emotional information’s effect on visual attention and VWM. Interestingly, contradictory findings have supported both a negative bias and a positive bias toward emotional faces (e.g. angry faces or happy faces) in the attention and VWM fields. We found that the classical paradigms—that is, the visual search paradigm in attention and the change detection paradigm in VWM—are considerably similar. The settings of these paradigms could be responsible for these contradictory results. In this paper, we compare previous controversial results from behavioral and neuroscience studies using these two paradigms. We suggest three possible contributing factors that have significant impacts on the controversial conclusion of different emotional bias effects, namely: stimulus choice, experimental setting, and cognitive process. Finally, we propose new research directions and guidelines for future studies.
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