Working Memory Content Is Distorted by Its Use in Perceptual Comparisons

Working memory flips the direction of serial bias through memory-based decision

Reported perception of a new stimulus is either attracted toward or repelled away from task-irrelevant prior stimuli. While prevailing theories propose that the opposing serial biases may stem from distinct stages of information processing, the exact role of working memory (WM) in the serial bias remains unclear despite its consistent involvement in nearly all pertinent studies. Additionally, it is not well understood whether this bias is primarily driven by the biased representation itself or by the decision-making process for the new stimulus. In the present study, we used an orientation delayed estimation paradigm with an attention-demanding intervening task, designed to disrupt the maintenance of stimulus information to investigate the role of WM in serial bias. In the analysis, we scrutinized the trajectory of mouse reports and response time to investigate how the response unfolds over time. Our findings indicate that the serial bias went from repulsive to attractive when WM maintenance was interrupted by the intervening task, and that the associated response trajectories and response time exhibited patterns that cannot be explained by the biased representation alone. These results demonstrate that the task-irrelevant prior stimulus influences the decision for the new stimulus, with the direction of the bias being determined by attentional demand during WM maintenance, thereby placing significant constraints on existing theories on the serial bias effect.

Repulsion bias is insensitive to spatial attention, yet expands during active working memory maintenance

Our brain sometimes represents visual information in a biased manner. Multiple visual features presented simultaneously or sequentially may interact with each other when we perceive them or maintain them in visual working memory (WM), giving rise to report bias. How goal-directed attention influences target representation is not fully understood, especially concerning whether attention towards distractors modulates report bias for the target. Our study investigated the WM biases of the target when it is concurrent with (1) one attended distractor only, (2) one unattended distractor only, and (3) both kinds of distractors during perception. It was found that the target WM is reported as being repelled away from concurrent distractors, attended or unattended, suggesting attention is not necessary for the occurrence of repulsion bias during perception. Furthermore, goal-directed attention towards the distractors modulates the strength of interitem interaction, and the repulsion bias was found to be stronger when attention was directed toward the distractor than when it was not. However, the exaggerated repulsion associated with the attended distractor is likely due to increased relevance to the memory task and (or) WM load instead of spatial attention. In contrast, spatial attention towards the distractor increases the chances of misreporting the distractor for the target.

Mapping visual working memory models to a theoretical framework

The body of research on visual working memory (VWM)-the system often described as a limited memory store of visual information in service of ongoing tasks-is growing rapidly. The discovery of numerous related phenomena, and the many subtly different definitions of working memory, signify a challenge to maintain a coherent theoretical framework to discuss concepts, compare models and design studies. A lack of robust theory development has been a noteworthy concern in the psychological sciences, thought to be a precursor to the reproducibility crisis (Oberauer & Lewandowsky, Psychonomic Bulletin & Review, 26, 1596-1618, 2019). I review the theoretical landscape of the VWM field by examining two prominent debates-whether VWM is object-based or feature-based, and whether discrete-slots or variable-precision best describe VWM limits. I share my concerns about the dualistic nature of these debates and the lack of clear model specification that prevents fully determined empirical tests. In hopes of promoting theory development, I provide a working theory map by using the broadly encompassing memory for latent representations model (Hedayati et al., Nature Human Behaviour, 6, 5, 2022) as a scaffold for relevant phenomena and current theories. I illustrate how opposing viewpoints can be brought into accordance, situating leading models of VWM to better identify their differences and improve their comparison. The hope is that the theory map will help VWM researchers get on the same page-clarifying hidden intuitions and aligning varying definitions-and become a useful device for meaningful discussions, development of models, and definitive empirical tests of theories.

Bend but don't break: Prioritization protects working memory from displacement but leaves it vulnerable to distortion from distraction

Perceptual distraction distorts visual working memory representations. Previous research has shown that memory responses are systematically biased towards passively viewed visual distractors that are similar to the memoranda. However, it remains unclear whether the prioritization of one working memory representation over another reduces the impact of perceptual distractors. We designed a study with five different types of visual distraction that varied in engagement and found evidence for both subtle distortions and catastrophic failures of memory. Importantly, prioritization protected working memories from catastrophic loss (fewer "swap errors") but rendered them more vulnerable to distortion (greater attractive "biases" towards the distractor). Our findings demonstrate that prioritization does not simply protect working memory from any and all interference, but rather it reduces the likelihood of catastrophic disruption from perceptual distraction at the cost of an increased likelihood of distortion.

Assessing the interaction between working memory and perception through time

Content maintained in visual working memory changes concurrent visual processing, suggesting that visual working memory may recruit an overlapping neural representation with visual perception. However, it remains unclear whether visual working memory representations persist as a sensory code through time, or are recoded later into an abstract code. Here, we directly contrasted a temporal decay + visual code account and a temporal decay + abstract code account within the temporal dynamics of the interaction between working memory and perception. By manipulating the ISI (inter-stimulus interval) between working memory encoding and a perceptual discrimination task, we found that task-relevant and therefore actively maintained perceptual information parametrically altered participants' ability to discriminate perceptual stimuli even 4 s after encoding, whereas task-irrelevant information caused only an acutely transient effect. While continuously present, the size of this shift in discrimination thresholds gradually decreased over time. Concomitantly, the size of the bias in working memory reports increased over time. The opposing directions of threshold and bias effects are consistent with the local maintenance of information in perceptual areas, explained by a temporal decay + visual code account. As the maintained representation decays over time, its ability to alter incoming perceptual signals decreases (reduced threshold effects) while its likelihood of being impacted by those same signals increases (increased bias effects). Altogether, these results suggest that the readout of working memory relies on a sensory representation at a cost of increased interference by ongoing perception.

Perceptual comparisons modulate memory biases induced by new visual inputs

It is well-established that stimulus-specific information in visual working memory (VWM) can be systematically biased by new perceptual inputs. These memory biases are commonly attributed to interference that arises when perceptual inputs are physically similar to VWM contents. However, recent work has suggested that explicitly comparing the similarity between VWM contents and new perceptual inputs modulates the size of memory biases above and beyond stimulus-driven effects. Here, we sought to directly investigate this modulation hypothesis by comparing the size of memory biases following explicit comparisons to those induced when new perceptual inputs are ignored (Experiment 1) or maintained in VWM alongside target information (Experiment 2). We found that VWM reports showed larger attraction biases following explicit perceptual comparisons than when new perceptual inputs were ignored or maintained in VWM. An analysis of participants' perceptual comparisons revealed that memory biases were amplified after perceptual inputs were endorsed as similar-but not dissimilar-to one's VWM representation. These patterns were found to persist even after accounting for variability in the physical similarity between the target and perceptual stimuli across trials, as well as the baseline memory precision between the distinct task demands. Together, these findings illustrate a causal role of perceptual comparisons in modulating naturally-occurring memory biases.

The role of motion in visual working memory for dynamic stimuli: More lagged but more precise representations of moving objects

While most visual working memory studies use static stimuli with unchanging features, objects in the real world are often dynamic, introducing significant differences in the surface feature information hitting the retina from the same object over time (e.g., changes in orientation, lighting, shadows). Previous research on dynamic stimuli has shown that change detection is improved if objects obey rules of physical motion, but it is unclear how memory for visual features interacts with object motion. In the current study, we investigated whether object motion facilitates greater temporal integration of continuously changing surface feature information. In a series of experiments, participants were asked to report the final color of continuously changing colored dots that were either moving or stationary on the screen. We found that the reported colors "lagged behind" the physical states of the dots when they were in motion. We also observed that the precision of memory responses was significantly higher for stimuli in the moving condition compared to the stationary condition. Together, these findings suggest that memory representation is improved - but lagged - for moving objects, consistent with the idea that object motion may facilitate integration of object information over longer intervals.

Flexible top-down control in the interaction between working memory and perception

Successful goal-directed behavior often requires continuous sensory processing while simultaneously maintaining task-related information in working memory (WM). Although WM and perception are known to interact, little is known about how their interactions are controlled. Here, we tested the hypothesis that WM perception interactions engage two distinct modes of control – proactive and reactive – in a manner similar to classic conflict-adaptation tasks (e.g. Stroop, flanker, and Simon). Participants performed a delayed recall-of-orientation WM task, plus a standalone visual discrimination-of-orientation task the occurred during the delay period, and with the congruity in orientation between the tasks manipulated. Proactive control was seen in the sensitivity of task performance to the previous trial's congruity (i.e. a Gratton effect). Reactive control was observed in a repulsive serial-dependence produced by incongruent discriminanda. Quantitatively, these effects were explained by parameters from a reinforcement learning-based model that tracks trial-to-trial fluctuations in control demand: reactive control by a phasic control prediction error (control PE), and proactive control by a tonic level of predicted conflict updated each trial by the control PE. Thus, WM-perception interactions may be controlled by the same mechanisms that govern conflict in other domains of cognition, such as response selection.

Breaking the cardinal rule: The impact of interitem interaction and attentional priority on the cardinal biases in orientation working memory

Although it is not typically assumed in influential models of visual working memory (WM), representations in WM are systematically biased by multiple factors. Orientation representations are biased away from the cardinal axis (i.e., cardinal bias) and they are biased away from or toward the other orientation simultaneously held in WM (i.e., interitem interaction). The present study investigated the extent to which these two bias mechanisms interact in WM. In Experiment 1, participants remembered two sequentially presented orientations and reproduced both orientations after a short delay. Cardinal biases were assessed separately for the trials where the two mechanisms produce biases in the same direction (i.e., congruent trials) and the trials where they produce biases in the opposite direction (i.e., incongruent trials). Whereas congruent trials exhibited a typical cardinal bias, incongruent trials exhibited no cardinal bias, demonstrating that the cardinal bias was canceled out by the interitem interaction. Follow-up experiments extended these results by manipulating attentional priority for the two orientations by means of precue (Experiment 2) and postcue (Experiment 3). In both experiments, attentionally prioritized items exhibited a typical cardinal bias irrespective of the congruency whereas attentionally unprioritized items exhibited a reversal of the cardinal bias in the incongruent trials, demonstrating that selective attention modulates the influence of the interitem interaction. Together, these results suggest that WM leverages information about specific stimuli and their relationship to support a given behavioral goal.