Working memory (WM) mechanisms for verbal, spatial, and object information have been extensively examined, yet those for kinetic information are less known. The current study explored the WM capacity and architecture of kinetic information by examining the maintenance of biological motion (BM) stimuli in WM. Human BM is the most salient and biologically significant kinetic information encountered in everyday life. We isolated motion signals of human BM from non-BM sources by using point-light displays as to-be-memorized BM. During a change detection task, we found that, at most, 3 to 4 BM stimuli could be retained in WM (Experiment 1). Next, we found that extra colors, spatial locations, or shapes remembered concurrently with BM stimuli (Experiments 2, 3, and 4, respectively), did not affect BM memory considerably. However, BM memory was affected by a concurrent memory task of non-BM movements (Experiment 5). These results support the hypothesis that an independent storage buffer of WM exists for kinetic information, which can hold up to 3 to 4 motion units.

Feature binding is a core concept in many research fields, including the study of working memory (WM). Over the past decade, it has been debated whether keeping the feature binding in visual WM consumes more visual attention than the constituent single features. Previous studies have only explored the contribution of domain-general attention or space-based attention in the binding process; no study so far has explored the role of object-based attention in retaining binding in visual WM. We hypothesized that object-based attention underlay the mechanism of rehearsing feature binding in visual WM. Therefore, during the maintenance phase of a visual WM task, we inserted a secondary mental rotation (Experiments 1-3), transparent motion (Experiment 4), or an object-based feature report task (Experiment 5) to consume the object-based attention available for binding. In line with the prediction of the object-based attention hypothesis, Experiments 1-5 revealed a more significant impairment for binding than for constituent single features. However, this selective binding impairment was not observed when inserting a space-based visual search task (Experiment 6). We conclude that object-based attention underlies the rehearsal of binding representation in visual WM.

BackgroundThe processing mechanisms of visual working memory (VWM) have been extensively explored in the recent decade. However, how the perceptual information is extracted into VWM remains largely unclear. The current study investigated this issue by testing whether the perceptual information was extracted into VWM via an integrated-object manner so that all the irrelevant information would be extracted (object hypothesis), or via a feature-based manner so that only the target-relevant information would be extracted (feature hypothesis), or via an analogous processing manner as that in visual perception (analogy hypothesis).Methodology/Principal FindingsHigh-discriminable information which is processed at the parallel stage of visual perception and fine-grained information which is processed via focal attention were selected as the representatives of perceptual information. The analogy hypothesis predicted that whereas high-discriminable information is extracted into VWM automatically, fine-grained information will be extracted only if it is task-relevant. By manipulating the information type of the irrelevant dimension in a change-detection task, we found that the performance was affected and the ERP component N270 was enhanced if a change between the probe and the memorized stimulus consisted of irrelevant high-discriminable information, but not if it consisted of irrelevant fine-grained information.Conclusions/SignificanceWe conclude that dissociated extraction mechanisms exist in VWM for information resolved via dissociated processes in visual perception (at least for the information tested in the current study), supporting the analogy hypothesis.

Mainstream theories of visual perception assume that visual working memory (VWM) is critical for integrating online perceptual information and constructing coherent visual experiences in changing environments. Given the dynamic interaction between online perception and VWM, we propose that how visual information is processed during visual perception can directly determine how the information is going to be selected, consolidated, and maintained in VWM. We demonstrate the validity of this hypothesis by investigating what kinds of perceptual information can be stored as integrated objects in VWM. Three criteria for object-based storage are introduced: (a) automatic selection of task-irrelevant features, (b) synchronous consolidation of multiple features, and (c) stable maintenance of feature conjunctions. The results show that the outputs of parallel perception meet all three criteria, as opposed to the outputs of serial attentive processing, which fail all three criteria. These results indicate that (a) perception and VWM are not two sequential processes, but are dynamically intertwined; (b) there are dissociated mechanisms in VWM for storing information identified at different stages of perception; and (c) the integrated object representations in VWM originate from the "preattentive" or "proto" objects created by parallel perception. These results suggest how visual perception, attention, and VWM can be explained by a unified framework.

Visual working memory (VWM) maintains and manipulates a limited set of visual objects being actively used in visual processing. To explore whether and how the fine detailed information is stored in VWM, four experiments have been conducted while recording the contralateral delay activity (CDA), an event-related potential difference wave that reflects the information maintenance in VWM. The type of the remembered information was manipulated by adopting simple objects and complex objects as materials. We found the amplitude of CDA was modulated by object complexity: as the set size of memory array rose from 2 to 4, the amplitude of CDA stopped increasing for maintaining complex objects with detailed information, while continued increasing for storing highly discriminable simple objects. These results suggest that VWM can store the fine detailed information; however it can not store all the fine detailed information from 4 complex objects. It implies that the capacity of VWM is not only characterized by a fixed number of objects, there is at least one stage influenced by the detailed information contained in the objects. These results are further discussed within a two-stage storing model of VWM: different types of perceptual information (highly discriminable features and fine detailed features) are maintained in VWM via two distinctive mechanisms.

Over the past decade, it has been debated whether retaining bindings in working memory (WM) requires more attention than retaining constituent features, focusing on domain-general attention and space-based attention. Recently, we proposed that retaining bindings in WM needs more object-based attention than retaining constituent features (Shen, Huang, & Gao, 2015, Journal of Experimental Psychology: Human Perception and Performance, doi: 10.1037/xhp0000018 ). However, only unitized visual bindings were examined; to establish the role of object-based attention in retaining bindings in WM, more emperical evidence is required. We tested 4 new bindings that had been suggested requiring no more attention than the constituent features in the WM maintenance phase: The two constituent features of binding were stored in different WM modules (cross-module binding, Experiment 1), from auditory and visual modalities (cross-modal binding, Experiment 2), or temporally (cross-time binding, Experiments 3) or spatially (cross-space binding, Experiments 4-6) separated. In the critical condition, we added a secondary object feature-report task during the delay interval of the change-detection task, such that the secondary task competed for object-based attention with the to-be-memorized stimuli. If more object-based attention is required for retaining bindings than for retaining constituent features, the secondary task should impair the binding performance to a larger degree relative to the performance of constituent features. Indeed, Experiments 1-6 consistently revealed a significantly larger impairment for bindings than for the constituent features, suggesting that object-based attention plays a pivotal role in retaining bindings in WM.

Working memory mechanisms for binding have been examined extensively in the last decade, yet few studies have explored bindings relating to human biological motion (BM). Human BM is the most salient and biologically significant kinetic information encountered in everyday life and is stored independently from other visual features (e.g., colors). The current study explored 3 critical issues of BM-related binding in working memory: (a) how many BM binding units can be retained in working memory, (b) whether involuntarily object-based binding occurs during BM binding, and (c) whether the maintenance of BM bindings in working memory requires attention above and beyond that needed to maintain the constituent dimensions. We isolated motion signals of human BM from non-BM sources by using point-light displays as to-be-memorized BM and presented the participants colored BM in a change detection task. We found that working memory capacity for BM-color bindings is rather low; only 1 or 2 BM-color bindings could be retained in working memory regardless of the presentation manners (Experiments 1-3). Furthermore, no object-based encoding took place for colored BM stimuli regardless of the processed dimensions (Experiments 4 and 5). Central executive attention contributes to the maintenance of BM-color bindings, yet maintaining BM bindings in working memory did not require more central attention than did maintaining the constituent dimensions in working memory (Experiment 6). Overall, these results suggest that keeping BM bindings in working memory is a fairly resource-demanding process, yet central executive attention does not play a special role in this cross-module binding.

Every day, people perceive other people performing interactive actions. Retaining these actions of human agents in working memory (WM) plays a pivotal role in a normal social life. However, whether the semantic knowledge embedded in the interactive actions has a pervasive impact on the storage of the actions in WM remains unknown. In the current study, we investigated two opposing hypotheses: (a) that WM stores the interactions individually (the individual-storage hypothesis) and (b) that WM stores the interactions as chunks (the chunk-storage hypothesis). We required participants to memorize a set of individual actions while ignoring the underlying social interactions. We found that although the social-interaction aspect was task irrelevant, the interactive actions were stored in WM as chunks that were not affected by memory load (Experiments 1 and 2); however, inverting the human actions vertically abolished this chunking effect (Experiment 3). These results suggest that WM automatically and efficiently used semantic knowledge about interactive actions to store them and support the chunk-storage hypothesis.