Blaire Dube

More than a filter: Feature-based attention regulates the distribution of visual working memory resources.

Across 2 experiments we revisited the filter account of how feature-based attention regulates visual working memory (VWM). Originally drawing from discrete-capacity (“slot”) models, the filter account proposes that attention operates like the “bouncer in the brain,” preventing distracting information from being encoded so that VWM resources are reserved for relevant information. Given recent challenges to the assumptions of discrete-capacity models, we investigated whether feature-based attention plays a broader role in regulating memory. Both experiments used partial report tasks in which participants memorized the colors of circle and square stimuli, and we provided a feature-based goal by manipulating the likelihood that 1 shape would be probed over the other across a range of probabilities. By decomposing participants’ responses using mixture and variable-precision models, we estimated the contributions of guesses, nontarget responses, and imprecise memory representations to their errors. Consistent with the filter account, participants were less likely to guess when the probed memory item matched the feature-based goal. Interestingly, this effect varied with goal strength, even across high probabilities where goal-matching information should always be prioritized, demonstrating strategic control over filter strength. Beyond this effect of attention on which stimuli were encoded, we also observed effects on how they were encoded: Estimates of both memory precision and nontarget errors varied continuously with feature-based attention. The results offer support for an extension to the filter account, where feature-based attention dynamically regulates the distribution of resources within working memory so that the most relevant items are encoded with the greatest precision.

Visual working memory simultaneously guides facilitation and inhibition during visual search

During visual search, visual working memory (VWM) supports the guidance of attention in two ways: It stores the identity of the search target, facilitating the selection of matching stimuli in the search array, and it maintains a record of the distractors processed during search so that they can be inhibited. In two experiments, we investigated whether the full contents of VWM can be used to support both of these abilities simultaneously. In Experiment 1, participants completed a preview search task in which (a) a subset of search distractors appeared before the remainder of the search items, affording participants the opportunity to inhibit them, and (b) the search target varied from trial to trial, requiring the search target template to be maintained in VWM. We observed the established signature of VWM-based inhibition—reduced ability to ignore previewed distractors when the number of distractors exceeds VWM’s capacity—suggesting that VWM can serve this role while also representing the target template. In Experiment 2, we replicated Experiment 1, but added to the search displays a singleton distractor that sometimes matched the color (a task-irrelevant feature) of the search target, to evaluate capture. We again observed the signature of VWM-based preview inhibition along with attentional capture by (and, thus, facilitation of) singletons matching the target template. These findings indicate that more than one VWM representation can bias attention at a time, and that these representations can separately affect selection through either facilitation or inhibition, placing constraints on existing models of the VWM-based guidance of attention.

Extraversion predicts superior face-specific recognition ability, but through experience, not positive affect

Experience is an important factor in developing face recognition ability. Given that extraverts show increased social involvement, extraversion may be associated with greater experience with faces, thereby leading to enhanced face recognition ability. However, extraverts also characteristically display high positive affect - an affective state thought to bias visual processing to be more global or holistic in nature. Given the large body of evidence suggesting that faces are processed holistically, positive affect may lead to superior face processing for extraverts aside from their increased social experiences (i.e. positive affect may mediate any relationship between extraversion and face recognition ability). To examine the relationships between extraversion, positive affect, and face and non-face recognition ability, university student participants completed self-report measures of personality and affect before completing the Cambridge Face Memory Task (CFMT), and a matched control task assessing recognition of cars (Cambridge Car Memory Task, CCMT). Each measure was taken twice, separated by one week. All measures showed very high test-retest reliability and scores were therefore averaged across both sessions. A face-specific recognition advantage was observed for individuals high in extraversion in that extraversion predicted better face recognition, even when controlling for non-face recognition. No relationships were observed between state or trait positive affect and recognition ability. Further, statistically controlling for affect strengthened the relationship between extraversion and face-specific recognition ability, suggesting that there is something inherent to extraversion aside from positive affect that benefits face recognition. We suggest that extraverts gregariousness allows greater opportunities for developing face expertise. Meeting abstract presented at VSS 2015.

Probabilistic retro-cues do not determine state in visual working memory

The effective use of our capacity-limited visual working memory (VWM) requires mechanisms that govern how it represents information. Validly cueing an item in VWM after encoding, for instance, enhances memory performance for that item and biases its state in VWM, bringing its representation to an active state such that attentional selection is biased towards perceptually similar inputs. Critically, when the retro-cue is less than 100% valid (i.e., probabilistic rather than deterministic), the effect of the cue on memory performance varies. Here we investigated whether deterministic and probabilistic retro-cues also differ in their influence over item state in VWM. Participants encoded two colored squares, and a retro-cue indicated which item was most likely to be probed in a subsequent memory test. Across blocks, we manipulated cue validity to be deterministic (100% valid) or probabilistic (70% valid). On a subset of trials, no memory probe was presented and the trial ended with a visual search task in which a colored distractor –matching the cued memory item, the non-cued item, or neither – was presented. Predictably, in the deterministic condition, the presence of a singleton distractor matching the cued item reliably slowed reaction times during visual search. In the probabilistic condition, however, there were no differences in reaction times when the singleton matched the cued item or the non-cued item, despite a reliable benefit to memory performance on valid memory trials. We suggest that, while probabilistic retro-cues improve memory of the cued item, they are not sufficient to bias its state in VWM.

Feature-based attention separately influences visual working memory resolution and encoding probability.

We use attention to select relevant portions of our environment for detailed processing-a process often directed by feature-based goals. Feature-based attention guides visual information processing by strengthening early representations (i.e., within perceptual cortex). Here we examined how feature-based goals affect the way visual information is represented at later stages of processing, namely within visual working memory (VWM). To address this question we used a continuous partial-report VWM task (i.e., a colour-wheel task) and measured the effects of attention on guess rate (the probability that an item is encoded into VWM) and standard deviation (the resolution with which an item is represented). On each trial of Experiment 1, participants remembered the colours of two squares and two circles over a delay, and then reported the colour of one probed stimulus. To manipulate feature-based attention we instructed participants that square stimuli were more likely to be probed (counterbalanced): Across four blocks, squares were probed on 60%, 70%, 80%, or 90% of trials. We found that increasing the value of a feature-based goal increases the probability that a goal-matching item will be encoded into VWM without altering its resolution. This pattern reverses, however, for non-matching stimuli: Attention affects resolution but not guess rate. In Experiment 2, we increased set size from four to six items (three circles and three squares), and observed the same effects of attention. The double dissociation observed in both experiments suggests that feature-based attention can affect both VWM encoding probability and resolution, and, for a given stimulus, these effects can emerge independently. Broadly, our findings add to recent studies investigating how the value of an attentional goal impacts VWM. Interestingly, as attention type (attend to feature vs. space) and stimulus type (report colour vs. location) change, so do the effects on VWM, suggesting a need for more research. Meeting abstract presented at VSS 2015.