Retro-cue benefits in working memory without sustained focal attention.

In working memory (WM) tasks, performance can be boosted by directing attention to one memory object: When a retro-cue in the retention interval indicates which object will be tested, responding is faster and more accurate (the retro-cue benefit). We tested whether the retro-cue benefit in WM depends on sustained attention to the cued object by inserting an attention-demanding interruption task between the retro-cue and the memory test. In the first experiment, the interruption task required participants to shift their visual attention away from the cued representation and to a visual classification task on colors. In the second and third experiments, the interruption task required participants to shift their focal attention within WM: Attention was directed away from the cued representation by probing another representation from the memory array prior to probing the cued object. The retro-cue benefit was not attenuated by shifts of perceptual attention or by shifts of attention within WM. We concluded that sustained attention is not needed to maintain the cued representation in a state of heightened accessibility.

Getting more from visual working memory: Retro-cues enhance retrieval and protect from visual interference.

Visual working memory (VWM) has a limited capacity. This limitation can be mitigated by the use of focused attention: if attention is drawn to the relevant working memory content before test, performance improves (the so-called retro-cue benefit). This study tests 2 explanations of the retro-cue benefit: (a) Focused attention protects memory representations from interference by visual input at test, and (b) focusing attention enhances retrieval. Across 6 experiments using color recognition and color reproduction tasks, we varied the amount of color interference at test, and the delay between a retrieval cue (i.e., the retro-cue) and the memory test. Retro-cue benefits were larger when the memory test introduced interfering visual stimuli, showing that the retro-cue effect is in part because of protection from visual interference. However, when visual interference was held constant, retro-cue benefits were still obtained whenever the retro-cue enabled retrieval of an object from VWM but delayed response selection. Our results show that accessible information in VWM might be lost in the processes of testing memory because of visual interference and incomplete retrieval. This is not an inevitable state of affairs, though: Focused attention can be used to get the most out of VWM. (PsycINFO Database Record

Refreshing memory traces: thinking of an item improves retrieval from visual working memory.

This article provides evidence that refreshing, a hypothetical attention-based process operating in working memory (WM), improves the accessibility of visual representations for recall. "Thinking of", one of several concurrently active representations, is assumed to refresh its trace in WM, protecting the representation from being forgotten. The link between refreshing and WM performance, however, has only been tenuously supported by empirical evidence. Here, we controlled which and how often individual items were refreshed in a color reconstruction task by presenting cues prompting participants to think of specific WM items during the retention interval. We show that the frequency with which an item is refreshed improves recall of this item from visual WM. Our study establishes a role of refreshing in recall from visual WM and provides a new method for studying the impact of refreshing on the amount of information we can keep accessible for ongoing cognition.

Unloading and reloading working memory: attending to one item frees capacity.

During the retention interval of a working memory task, presenting a retro-cue directs attention to 1 of the items in working memory. Testing the cued item leads to faster and more accurate responses. We contrasted 5 explanations of this benefit: (a) removal of noncued items, (b) strengthening of the cued item, (c) protection from probe interference, (d) protection from degradation, and (e) prioritization during the decision process. Experiment 1 showed that retro-cues reduced the set size effect in a visual recognition task, and did so increasingly with more time available to use the retro-cue. This finding is predicted only by Hypotheses 1 and 2. Hypotheses 3 through 5 were ruled out as explanations of the retro-cue benefit in this experiment. In Experiments 2 and 3, participants encoded 2 sequentially presented memory sets. In half of the trials, 1 item from the first set was retro-cued during the interset interval. Retro-cues improved memory for the second set. This reloading benefit is predicted only by the removal hypothesis: Irrelevant contents are removed from working memory, freeing capacity to encode new contents. Experiment 3 also yielded evidence that strengthening of the cued item might contribute to the retro-cue effect.

Spatial transposition gradients in visual working memory.

In list memory, access to individual items reflects limits of temporal distinctiveness. This is reflected in the finding that neighbouring list items tend to be confused most often. This article investigates the analogous effect of spatial proximity in a visual working-memory task. Items were presented in different locations varying in spatial distance. A retro-cue indicated the location of the item relevant for the subsequent memory test. In two recognition experiments, probes matching spatially close neighbours of the relevant item led to more false alarms than probes matching distant neighbours or non-neighbouring memory items. In two probed-recall experiments, one with simultaneous, the other with sequential memory item presentation, items closer to the cued location were more frequently chosen for recall than more distant items. These results reflect a spatial transposition gradient analogous to the temporal transposition gradient in serial recall and challenge fixed-capacity models of visual working memory (WM).

Focused attention improves working memory: implications for flexible-resource and discrete-capacity models.

Performance in working memory (WM) tasks depends on the capacity for storing objects and on the allocation of attention to these objects. Here, we explored how capacity models need to be augmented to account for the benefit of focusing attention on the target of recall. Participants encoded six colored disks (Experiment 1) or a set of one to eight colored disks (Experiment 2) and were cued to recall the color of a target on a color wheel. In the no-delay condition, the recall-cue was presented after a 1,000-ms retention interval, and participants could report the retrieved color immediately. In the delay condition, the recall-cue was presented at the same time as in the no-delay condition, but the opportunity to report the color was delayed. During this delay, participants could focus attention exclusively on the target. Responses deviated less from the target's color in the delay than in the no-delay condition. Mixture modeling assigned this benefit to a reduction in guessing (Experiments 1 and 2) and transposition errors (Experiment 2). We tested several computational models implementing flexible or discrete capacity allocation, aiming to explain both the effect of set size, reflecting the limited capacity of WM, and the effect of delay, reflecting the role of attention to WM representations. Both models fit the data better when a spatially graded source of transposition error is added to its assumptions. The benefits of focusing attention could be explained by allocating to this object a higher proportion of the capacity to represent color.

Focused, unfocused, and defocused information in working memory.

The study investigated the effect of selection cues in working memory (WM) on the fate of not-selected contents of WM. Experiments 1A and 1B showed that focusing on 1 cued item in WM does not impair memory for the remaining items. The nonfocused items are maintained in WM even when this is not required by the task. Experiments 2 and 3 showed that items that were once focused in WM remain strengthened after the focus shifts away from them. When defocused items are presented as mismatching recognition probes, they are rejected better than other mismatching probes (Experiments 2 and 3). When a defocused item was later cued again, such that the focus had to shift back to it, that item was recognized better than an item cued for the first time (Experiment 3). The results support the distinction between mechanisms for temporary maintenance and the focus of attention in WM, and they challenge theories that explain maintenance and focusing by the same mechanisms, such as a limited number of slots or a limited resource.