Dimension-based retro-cue benefit in working memory does not require unfocused dimension removal

All identical objects reduce memory load at the late maintenance stage in working memory

Visual working memory (VWM) is critical for temporarily storing and manipulating visual information but is limited in capacity. Previous research suggests that perceptual organization, such as grouping identical objects, may alleviate VWM resource constraints, yet the underlying mechanisms remain unclear. This study investigated whether identical orientation stimuli reduce VWM resource consumption and whether this reduction occurs during encoding or maintenance phase. Using the contralateral delay activity (CDA), an event-related potential (ERP) component that indexes the number of items stored in VWM, we examined three memory conditions: all-same (i.e., four identical orientations), partial-same (i.e., two pairs of identical orientations), and all-different (i.e., four different orientations) conditions. Behavioral results showed improved VWM performance as the number of identical orientations increased, with the highest performance in the all-same condition. ERP results revealed no significant differences in early CDA amplitudes across conditions, suggesting that identical stimuli do not reduce VWM resource consumption during early maintenance phase. However, late CDA amplitudes were significantly reduced in the all-same condition compared to the partial-same and all-different conditions, indicating that the benefits of identical objects emerge during the late maintenance phase. Notably, partially identical stimuli did not reduce VWM load, highlighting the complexity of integrating partially redundant information. These findings highlight the distinct contributions of early consolidation and maintenance phases in optimizing VWM through perceptual grouping and provide evidence that the facilitative effect of identical objects relies on their complete repetition and late-stage cognitive processes.

Comparing retro-cue benefit mechanisms in visual working memory: completely valid vs. highly valid retro-cues

Visual working memory (VWM) plays a crucial role in temporarily maintaining and manipulating visual information. Retro-cue benefit (RCB) refers to the enhancement of memory performance when attention is directed toward a subset of items in VWM after their initial encoding. Our recent electroencephalogram (EEG) studies indicate that cue validity affects the mechanisms underlying RCB formation. However, previous research has not thoroughly examined whether these mechanisms differ between completely valid and highly valid cue conditions. This study investigates the consistency of RCB mechanisms under conditions of complete (100%) and high (80%) retro-cue validity. We manipulated retro-cue validity and examined cognitive processing mechanisms under different validity conditions using EEG. Specifically, we focused on the N2pc component, which reflects attentional resource allocation, and the contralateral delay activity (CDA) component, which reflects the quantity of information retained in VWM. The results, encompassing both behavioral and event-related potential (ERP) findings, show that participants in both the 100% and 80% cue validity conditions exhibit robust RCB. Notably, the degree of RCB remains consistent across these conditions, indicating that participants utilize retro-cues to enhance VWM performance to the same extent. In the 80% cue validity condition, a significant retro-cue cost (RCC) was observed, indicating that participants selectively discarded uncued items from VWM. In invalid trials, response accuracy drops to chance levels, supporting the removal hypothesis. ERP results reveal that attentional resource allocation (N2pc) and the quantity of retained information (CDA) remain uniform across cue validity conditions. The mechanism responsible for RCB formation appears to involve an all-or-nothing process of discarding uncued information rather than a flexible resource allocation strategy. This study provides insights into attention allocation and information-processing mechanisms in VWM, suggesting that conclusions drawn from tasks with completely valid retro-cues can be integrated with findings from highly valid cue tasks. These findings also illuminate the flexibility of internal attentional resource allocation during RCB formation and contribute to our understanding of attention processes in VWM.