The Contralateral Delay Activity Tracks the Sequential Loading of Objects into Visual Working Memory, Unlike Lateralized Alpha Oscillations

Visual working memory temporarily represents a continuous stream of task-relevant objects as we move through our environment performing tasks. Previous work has identified candidate neural mechanisms of visual working memory storage; however, we do not know which of these mechanisms enable the storage of objects as we sequentially encounter them in our environment. Here, we measured the contralateral delay activity (CDA) and lateralized alpha oscillations as human subjects were shown a series of objects that they needed to remember. The amplitude of CDA increased following the presentation of each to-be-remembered object, reaching asymptote at about three to four objects. In contrast, the concurrently measured lateralized alpha power remained constant with each additional object. Our results suggest that the CDA indexes the storage of objects in visual working memory, whereas lateralized alpha suppression indexes the focusing of attention on the to-be-remembered objects

Asymmetrical access to color and location in visual working memory

Models of visual working memory (VWM) have benefitted greatly from the use of the delayed-matching paradigm. However, in this task, the ability to recall a probed feature is confounded with the ability to maintain the proper binding between the feature that is to be reported and the feature (typically location) that is used to cue a particular item for report. Given that location is typically used as a cue-feature, we used the delayed-estimation paradigm to compare memory for location to memory for color, rotating which feature was used as a cue and which was reported. Our results revealed several novel findings: 1) the likelihood of reporting a probed object’s feature was superior when reporting location with a color cue than when reporting color with a location cue; 2) location report errors were composed entirely of swap errors, with little to no random location reports; and 3) both colour and location reports greatly benefitted from the presence of nonprobed items at test. This last finding suggests that it is uncertainty over the bindings between locations and colors at memory retrieval that drive swap errors, not at encoding. We interpret our findings as consistent with a representational architecture that nests remembered object features within remembered locations

More than a memory: Confirmatory visual search is not caused by remembering a visual feature

Previous research has demonstrated a preference for positive over negative information in visual search; asking whether a target object is green biases search towards green objects, even when this entails more perceptual processing than searching non-green objects. The present study investigated whether this confirmatory search bias is due to the presence of one particular (e.g., green) color in memory during search. Across two experiments, we show that this is not the critical factor in generating a confirmation bias in search. Search slowed proportionally to the number of stimuli whose color matched the color held in memory only when the color was remembered as part of the search instructions. These results suggest that biased search for information is due to a particular attentional selection strategy, and not to memory-driven attentional biases

Do we remember templates better so that we can reject distractors better?

Feature Integration Theory proposed that attention shifted between target-like representations in our visual field. However, the nature of the representations that determined what was target like received less specification than the nature of the attention shifts. In recent years, visual search research has focused on the nature of the memory representations that we use to guide our shifts of attention. Sensitive measures of memory quality indicate that the template representations are remembered better than other, merely maintained, memories. Here we tested the hypothesis that we prepare for difficult search tasks by storing a higher fidelity target representation in working memory than we do when preparing for an easy search task. To test this hypothesis, we explicitly tested participants’ memory of the target color they searched for (i.e., the attentional template) versus another memory that was not used to guide attention (i.e., an accessory representation) following blocks of searches with easy-to-find targets (i.e., distractors were homogeneously colored) to blocks of searches with hard-to-find targets (i.e., distractors were heterogeneously colored). Although homogeneous-distractor searches required minimal precision for distractor rejection, we found that templates were still remembered better than accessories, just like we found in a heterogeneous-distractor search. As a consequence, we suggest that stronger memories for templates likely reflects the need to decide whether new perceptual inputs match the template, and not an attempt to create a better template representation in anticipation of difficult searches

Go-getters and procrastinators: Investigating individual differences in visual cognition across university semesters

University-based psychological research typically relies on the participation of undergraduate students for data collection. Using this particular sample brings with it several possible issues, including the self-scheduling done by the participants. Research on performance between students who sign up early versus late in the semester has been inconsistent. Some research report benefits for early participant semesters, while others find no differences between the two groups. Anecdotally, it seems that the former holds true, as many researchers worry about the data collected late in the semester, sometimes opting for more motivated earlier participants in the next semester. The purpose of our study was to examine for the effect of time of semester across a well-known set of visual cognition tasks. To do so, participants completed canonical versions of a rapid serial visual presentation task, a flanker task, an additional singleton paradigm task, a multiple object tracking task and a visual working memory task. These tasks were chosen as typical measures of executive control, temporal selectivity, visual working memory capacity, resistance to distraction, and attentional capacity. Crucially, we correlated task performance with time of semester students chose to participate. Our results demonstrate that there were no significant differences in any of the tasks across semester timing. Furthermore, our findings support the validity of cognitive research relying on the system of recruiting undergraduate students from volunteer pools where students can self-select the time of the semester they undertake the experiments

Ironic capture: top-down expectations exacerbate distraction in visual search

Ironic processing refers to the phenomenon where attempting to resist doing something results in a person doing that very thing. Here, we report three experiments investigating the role of ironic processing in visual search. In Experiment 1, we informed observers that they could predict the location of a salient color singleton in a visual search task and found that response times were slower in that condition than in a condition where the singleton’s location was random. Experiment 2 used the same experimental design but did not inform participants of the color singleton’s behavior. Experiment 3 showed that the cost in the predictable condition was not due to dual task costs or block order effects and participants attempting to use the strategy showed a larger cost in the predictable condition than those who abandoned using that location foreknowledge. In this case, responses in the predictable color singleton condition were equivalent with the random color singleton condition. This suggests that having more knowledge about an upcoming, salient distractor ironically increases its interfering influence on performance

Long-term facilitation of return: A response-retrieval effect

The present study used a target–target procedure to examine the extent to which perceptual and response factors contribute to inhibition of return (IOR) in a visual discrimination task. When the target was perceptually identical to the previous target and the required response was the same, facilitation was observed for both standard and long-term target–target stimulus onset asynchronies (SOAs). When the color of the previous target differed from that of the current target but the response remained the same, facilitation was reduced in both the standard SOA and long-term SOA conditions. Finally, IOR was observed for both standard and long-term SOAs only in the condition in which there was a change in response. This pattern of inhibition and facilitation provides new evidence that the responses previously associated with a location play an important role in the ability to respond to a stimulus. We interpret this finding as consistent with a framework in which the involuntary retrieval of bound stimulus–response episodes contributes to response compatibility effects in visual stimulus discrimination

Temporal trimming: Evidence that common-onset masking shortens perceptual sampling of conscious object representations

Common-onset masking (COM) refers to a methodology where a mask can impair awareness of an object if the mask’s offset is delayed relative to the offset of the object. This method has classically been used to understand how discontinuities in visual input lead to the discrete removal of object representations before they reach conscious awareness. However, COM has recently been shown to reduce the precision of conscious object representations (Harrison, Rajsic, & Wilson, Psychonomic Bulletin & Review, 23(1), 180–186, 2016). As a result, Harrison et al. proposed that COM shortens the temporal window for perceptual sampling of an object’s representation, an account consistent with interruption-based theories of masking. In the present study we modified the standard COM methodology to assess the impact of a delayed mask offset on the temporal perception of an object’s representation. Across two experiments we provide novel evidence that a delayed mask offset can impair temporal perception of a conscious percept, such that it reduces the percept’s perceived duration (Experiment 1), and prematurely terminates updating of the percept’s dynamic orientation (Experiment 2). We refer to these results as temporal trimming, and suggest that the mechanism responsible for COM operates during the sustained perception of an object

Object-substitution masking degrades the quality of conscious object representations

Object-substitution masking (OSM) is a unique paradigm for the examination of object updating processes. However, existing models of OSM are underspecified with respect to the impact of object updating on the quality of target representations. Using two paradigms of OSM combined with a mixture model analysis we examine the impact of post-perceptual processes on a target’s representational quality within conscious awareness. We conclude that object updating processes responsible for OSM cause degradation in the precision of object representations. These findings contribute to a growing body of research advocating for the application of mixture model analysis to the study of how cognitive processes impact the quality (i.e., precision) of object representation

Confirmation bias in visual search.

In a series of experiments, we investigated the ubiquity of confirmation bias in cognition by measuring whether visual selection is prioritized for information that would confirm a proposition about a visual display. We show that attention is preferentially deployed to stimuli matching a target template, even when alternate strategies would reduce the number of searches necessary. We argue that this effect is an involuntary consequence of goal-directed processing, and show that it can be reduced when ample time is provided to prepare for search. These results support the notion that capacity-limited cognitive processes contribute to the biased selection of information that characterizes confirmation bias