Decoding working memory content from attentional biases

More attention with less working memory: The active inhibition of attended but outdated information

Attention has traditionally been regarded as a gateway to working memory, and almost all theoretical frameworks of attention and working memory assume that individuals always have a better memory for information that has received more attention. Here, we provide a series of counterintuitive demonstrations that show that paying more attention to a piece of information impedes, rather than enhances, the selection of this information into working memory. Experiments 1 to 5 provide converging evidence for an even weaker working memory trace of fully attended but outdated features, compared with baseline irrelevant features that were completely ignored. This indicates that the brain actively inhibits attended but outdated information to prevent it from entering working memory. Experiment 6 demonstrates that this inhibition processing is subject to executive control. These findings lead to a substantial reinterpretation of the relationship between attention and working memory.

Perceptual distraction causes visual memory encoding intrusions

Given the complexity of our visual environments, a number of mechanisms help us prioritize goal-consistent visual information. When searching for a friend in a crowd, for instance, visual working memory (VWM) maintains a representation of your target (i.e., your friend's shirt) so that attention can be subsequently guided toward target-matching features. In turn, attentional filters gate access to VWM to ensure that only the most relevant information is encoded and used to guide behavior. Distracting (i.e., unexpected/salient) information, however, can also capture your attention, disrupting search. In the current study we ask: does distraction also disrupt control over the VWM filter? Although the effect of distraction on search behavior is heavily studied, we know little about its consequences for VWM. Participants performed two consecutive visual search tasks on each trial. Stimulus color was irrelevant for both search tasks, but on trials where a salient distractor appeared on Search 1, we found evidence that the color associated with this distractor was incidentally encoded into VWM, resulting in memory-driven capture on Search 2. In two different experiments we observed slower responses on Search 2 when a non-target item matched the color of the salient distractor from Search 1; this effect was specific to the color associated with salient distraction and not induced by other non-target colors from the Search 1 display. We propose a novel Filter Disruption Theory: distraction disrupts the attentional filter that controls access to VWM, resulting in the encoding of irrelevant inputs at the time of capture.

Theoretical distinction between functional states in working memory and their corresponding neural states

Working memory (WM) is important for guiding behaviour, but not always for the next possible action. Here we define a WM item that is currently relevant for guiding behaviour as the functionally "active" item; whereas items maintained in WM, but not immediately relevant to behaviour, are defined as functionally "latent". Traditional neurophysiological theories of WM proposed that content is maintained via persistent neural activity (e.g., stable attractors); however, more recent theories have highlighted the potential role for "activity-silent" mechanisms (e.g., short-term synaptic plasticity). Given these somewhat parallel dichotomies, functionally active and latent cognitive states of WM have been associated with storage based on persistent-activity and activity-silent neural mechanisms, respectively. However, in this article we caution against a one-to-one correspondence between functional and activity states. We argue that the principal theoretical requirement for active and latent WM is that the corresponding neural states play qualitatively different functional roles. We consider a number of candidate solutions, and conclude that the neurophysiological mechanisms for functionally active and latent WM items are theoretically independent of the distinction between persistent activity-based and activity-silent forms of WM storage.

Guidance and selection history in hybrid foraging visual search

In Hybrid Foraging tasks, observers search for multiple instances of several types of target. Collecting all the dirty laundry and kitchenware out of a child's room would be a real-world example. How are such foraging episodes structured? A series of four experiments shows that selection of one item from the display makes it more likely that the next item will be of the same type. This pattern holds if the targets are defined by basic features like color and shape but not if they are defined by their identity (e.g., the letters p & d). Additionally, switching between target types during search is expensive in time, with longer response times between successive selections if the target type changes than if they are the same. Finally, the decision to leave a screen/patch for the next screen in these foraging tasks is imperfectly consistent with the predictions of optimal foraging theory. The results of these hybrid foraging studies cast new light on the ways in which prior selection history guides subsequent visual search in general.

Quantifying the Attentional Impact of Working Memory Matching Targets and Distractors

Various theoretical proposals have been put forward to explain how memory representations control attention during visual search. In this study, we use the first saccade on each trial as away to quantify the attentional impact of multiple types of representations held in working memory. Across two experiments, we found that a search target maintained in working memory was attended over 20 times more frequently than a non-memory-matching distractor. In addition, an item matching an additional object represented in working memory was attended 2 times more frequently than a non-memory matching distractor. These findings show that there is a measurable attentional impact of items maintained in working memory for a future task, however, such representations have a much weaker attentional impact than working memory representations of search targets.

Working memory-driven attention towards a distractor does not interfere with target feature perception

The contents of working memory (WM) can influence where we attend-but can it also interfere with what we see? Active maintenance of visual items in WM biases attention towards WM-matching objects, and also enhances early perceptual processing of WM-matching items (e.g., more accurate perceptual discrimination). Here, we asked whether a WM-matching distractor interferes with perceptual processing of a target's features. In a dual-task paradigm, participants maintained a shape in WM across an intervening visual search task, during which they had to reproduce the colour of a designated target item using a continuous-report technique. Importantly, the WM shape could match the target item, a distractor item, or no item in the search array. When the WM shape matched a distractor, we found no evidence of systematic perceptual interference (i.e., swapping or mixing with the distractor colour), but observed only general disruptions in target processing (i.e., decreased target accuracy). These results suggest that when visual attention is inadvertently drawn to a WM-matching distractor, any resultant automatic perceptual processing may be too transient or weak to significantly interfere with perceptual processing of the target's features.

Working Memory-Driven Attention in Real-World Search

People's attention is well attracted to stimuli matching their working memory. This memory-driven attentional capture has been demonstrated in simplified and controlled laboratory settings. The present study investigated whether working memory contents capture attention in a setting that closely resembles real-world environment. In the experiment, participants performed a task of searching for a target object in real-world indoor scenes, while maintaining a visual object in working memory. To create a setting similar to real-world environment, images taken from IKEA®'s online catalogue were used. The results showed that participants' attention was biased toward a working memory-matching object, interfering with the target search. This was so even when participants did not expect that a memory-matching stimulus would appear in the search array. These results suggest that working memory can bias attention in complex, natural environment and this memory-driven attentional capture in real-world setting takes place in an automatic manner.

Behavioral decoding of working memory items inside and outside the focus of attention

How we attend to our thoughts affects how we attend to our environment. Holding information in working memory can automatically bias visual attention toward matching information. By observing attentional biases on reaction times to visual search during a memory delay, it is possible to reconstruct the source of that bias using machine learning techniques and thereby behaviorally decode the content of working memory. Can this be done when more than one item is held in working memory? There is some evidence that multiple items can simultaneously bias attention, but the effects have been inconsistent. One explanation may be that items are stored in different states depending on the current task demands. Recent models propose functionally distinct states of representation for items inside versus outside the focus of attention. Here, we use behavioral decoding to evaluate whether multiple memory items-including temporarily irrelevant items outside the focus of attention-exert biases on visual attention. Only the single item in the focus of attention was decodable. The other item showed a brief attentional bias that dissipated until it returned to the focus of attention. These results support the idea of dynamic, flexible states of working memory across time and priority.

Cognitive control over prospective task-set interference

Recent studies have demonstrated that maintaining task-sets in working memory (WM) for prospective implementation can interfere with performance on an intervening task when the same stimulus requires incompatible responses in the ongoing versus the prospective task. This prospective task-set interference effect has previously been conceptualized as an obligatory process, resulting from instruction-based reflexivity (IBR). However, the extent to which strategic control can be exerted over interference in ongoing behavior from prospective task-sets held in WM has heretofore not been tested directly. To probe for strategic control over this effect, the authors conducted 3 experiments using a common inducer-diagnostic task design that manipulated the proportion compatibility of trials in the ongoing task. They hypothesized that if prospective task-set interference were malleable by control, participants would suppress the influence of the prospective set on ongoing processing when incompatible trials are frequent. Consistent with this prediction, the results show that prospective task-set interference is subject to modulation by strategic control such that the magnitude of interference is reduced, eliminated, or reversed in the presence of frequent incompatible trials. Thus, the influence on ongoing behavior of a prospective task-set held in WM is not obligatory, but subject to strategic control. (PsycINFO Database Record