The Many Facets of Individual Differences in Working Memory Capacity

Mental counters as an online tool for assessing working memory capacity

Working memory capacity (WMC) describes an individual's ability to focus their attention in the face of interference which allows them to actively maintain and manipulate information in immediate memory. Individual differences in WMC predict a wide range of psychological constructs. The development of online measures can enable data collection from broader, more diverse samples than those typically collected in person in laboratory settings. In addition, logistical challenges brought on by the COVID-19 pandemic have mandated the need for reliable and valid remote assessments of individual differences that are both culture-fair and less susceptible to cheating. This study reports details of a new online version of a Mental Counters task that takes only 10 min to collect and provides evidence for its reliability and convergent validity with other measures including Picture Span and Paper Folding.

Knowledge Representations: Individual Differences in Novel Problem Solving

The present study investigates how the quality of knowledge representations contributes to rule transfer in a problem-solving context and how working memory capacity (WMC) might contribute to the subsequent failure or success in transferring the relevant information. Participants were trained on individual figural analogy rules and then asked to rate the subjective similarity of the rules to determine how abstract their rule representations were. This rule representation score, along with other measures (WMC and fluid intelligence measures), was used to predict accuracy on a set of novel figural analogy test items, of which half included only the trained rules, and half were comprised of entirely new rules. The results indicated that the training improved performance on the test items and that WMC largely explained the ability to transfer rules. Although the rule representation scores did not predict accuracy on the trained items, rule representation scores did uniquely explain performance on the figural analogies task, even after accounting for WMC and fluid intelligence. These results indicate that WMC plays a large role in knowledge transfer, even when transferring to a more complex problem-solving context, and that rule representations may be important for novel problem solving.

The influence of working memory capacity and lapses of attention for variation in error monitoring

In two experiments, individual differences in working memory capacity (WMC), lapses of attention, and error monitoring were examined. Participants completed multiple WMC tasks along with a version of the Stroop task. During the Stroop, pupil diameter was continuously monitored. In both experiments, error phasic pupillary responses were larger than phasic pupillary responses associated with correct incongruent and correct congruent trials. WMC and indicators of lapses of attention were correlated with error pupillary response, suggesting that high WMC and low lapse individuals had enhanced error monitoring abilities compared with low WMC and high lapse individuals. Furthermore, in Experiment 2 error awareness abilities were associated with WMC, lapses of attention, and the error phasic pupillary responses. Importantly, individual differences in the susceptibility to lapses of attention largely accounted for the relationship between WMC and error monitoring in both experiments. Collectively, these results suggest that WMC is related to error monitoring abilities, but this association is largely due to individual differences in the ability to consistently maintain task engagement and avoid lapses of attention.

Cue overlap supports preretrieval selection in episodic memory: ERP evidence

People often want to recall events of a particular kind, but this selective remembering is not always possible. We contrasted two candidate mechanisms: the overlap between retrieval cues and stored memory traces, and the ease of recollection. In two preregistered experiments (Ns = 28), we used event-related potentials (ERPs) to quantify selection occurring before retrieval and the goal states — retrieval orientations — thought to achieve this selection. Participants viewed object pictures or heard object names, and one of these sources was designated as targets in each memory test. We manipulated cue overlap by probing memory with visual names (Experiment 1) or line drawings (Experiment 2). Results revealed that regardless of which source was targeted, the left parietal ERP effect indexing recollection was selective when test cues overlapped more with the targeted than non-targeted information, despite consistently better memory for pictures. ERPs for unstudied items also were more positive-going when cue overlap was high, suggesting that engagement of retrieval orientations reflected availability of external cues matching the targeted source. The data support the view that selection can act before recollection if there is sufficient overlap between retrieval cues and targeted versus competing memory traces.

The Cognitive Underpinnings of Multiply-Constrained Problem Solving

Individuals encounter problems daily wherein varying numbers of constraints require delimitation of memory to target goal-satisfying information. Multiply-constrained problems, such as the compound remote associates, are commonly used to study this type of problem solving. Since their development, multiply-constrained problems have been theoretically and empirically related to creative thinking, analytical problem solving, insight problem solving, and a multitude of other cognitive abilities. In the present study, we empirically evaluated the range of cognitive abilities previously associated with multiply-constrained problem solving to assess common versus unique predictive variance (i.e., working memory, attention control, episodic and semantic memory, and fluid and crystallized intelligence). Additionally, we sought to determine whether problem-solving ability and self-reported strategy adoption (analytical or insightful) were task specific or task general through the use of novel multiply-constrained problem-solving tasks (TriBond and Location Bond). Performance across these tasks was shown to be domain general, solutions derived through insightful strategies were more often correct than those derived through analytical strategies, and crystallized intelligence was the sole cognitive ability that provided unique predictive value after accounting for all other abilities.

Is working memory capacity related to baseline pupil diameter?

The relation between working memory capacity (WMC) and baseline pupil diameter was examined. Participants (N = 341) performed several WMC tasks and baseline pupil diameter was measured in a dark room with a black background screen. The results indicated a weak and non-significant correlation between WMC and baseline pupil diameter consistent with some prior research. A meta-analysis of available studies (k = 26; N = 4356) similarly indicated a weak and non-significant correlation between WMC and baseline pupil diameter. Moderator analyses indicated that the primary moderator responsible for heterogeneity across studies was where the study was conducted. Studies from one laboratory tend to demonstrate a significant positive correlation, whereas other laboratories have yet to demonstrate the correlation. Broadly, the results suggest that the correlation between WMC and baseline pupil diameter is weak and not particularly robust.

When working memory mechanisms compete: Predicting cognitive flexibility versus mental set

Cognitive flexibility is a hallmark of individuals with higher working memory capacity (WMC). Yet, individuals with higher WMC sometimes demonstrate greater rigidity in problem solving. The present research examines a novel account for these contradictory findings-that different WMC mechanisms support versus constrain cognitive flexibility. Across three studies, participants completed the water jug task-a problem-solving task requiring them to first establish and then break mental set. Predictor measures targeted three WMC mechanisms: attention control, primary memory, and secondary memory. In Study 1, primary and secondary memory predicted breaking mental set in opposite directions. Higher primary memory facilitated breaking mental set, whereas higher secondary memory hindered it. Study 2 demonstrated that attention control moderates these effects. Study 3 replicated these results using a less restrictive sampling procedure (i.e., participants were provided the strategy needed to establish mental set). The present research supports the proposed theory of functional opponency in WMC.

Aiding the search: Examining individual differences in multiply-constrained problem solving

Understanding and resolving complex problems is of vital importance in daily life. Problems can be defined by the limitations they place on the problem solver. Multiply-constrained problems are traditionally examined with the compound remote associates task (CRAT). Performance on the CRAT is partially dependent on an individual's working memory capacity (WMC). These findings suggest that executive processes are critical for problem solving and that there are reliable individual differences in multiply-constrained problem solving abilities. The goals of the current study are to replicate and further elucidate the relation between WMC and CRAT performance. To achieve these goals, we manipulated preexposure to CRAT solutions and measured WMC with complex-span tasks. In Experiment 1, we report evidence that preexposure to CRAT solutions improved problem solving accuracy, WMC was correlated with problem solving accuracy, and that WMC did not moderate the effect of preexposure on problem solving accuracy. In Experiment 2, we preexposed participants to correct and incorrect solutions. We replicated Experiment 1 and found that WMC moderates the effect of exposure to CRAT solutions such that high WMC participants benefit more from preexposure to correct solutions than low WMC (although low WMC participants have preexposure benefits as well). Broadly, these results are consistent with theories of working memory and problem solving that suggest a mediating role of attention control processes.

Item-method directed forgetting and working memory capacity: A hierarchical multinomial modeling approach

Intentional forgetting of information that has recently been encoded is regarded an active and adaptive process and is widely studied using the item-method or the list-method directed forgetting (DF) paradigm. In the present research, we tested whether inter-individual differences in working-memory capacity (WMC), that have been identified as a relevant predictor of DF within the list method, are also related to stronger DF effects within the item method. Furthermore, we investigated relationships between WMC and item-method DF at different processing stages by applying the multinomial storage–retrieval model hierarchically to our data. Results showed that individuals with high WMC are better able to store to-be-remembered information than individuals with low WMC, whereas WMC was not related to retrieval of to-be-remembered information or to either storage or retrieval of to-be-forgotten information. Implications for theoretical accounts of item-method DF are discussed.

When people's judgments of learning (JOLs) are extremely accurate at predicting subsequent recall: the "Displaced-JOL effect"

Judgments of learning (JOL) made after a delay more accurately predict subsequent recall than JOLs made immediately after learning. One explanation is that delayed JOLs involve retrieving information about the target item from secondary memory, whereas immediate JOLs involve retrieval from primary memory. One view of working memory claims that information in primary memory is displaced to secondary memory when attention is shifted to a secondary task. Thus, immediate JOLs might be as accurate as delayed JOLs if an intervening task displaces the target item from primary memory, requiring retrieval from secondary memory, prior to making the JOL. In four experiments, participants saw related word-pairs and made JOLs predicting later recall of the item. In Experiment 1, delayed JOLs were more accurate than JOLs made shortly after learning, regardless of whether a secondary task intervened between learning and JOL. In Experiments 2-4, the secondary task demands increased and JOLs made shortly after learning with an intervening task were just as accurate as delayed JOLs, and both were more accurate than immediate JOLs with no intervening task (Experiment 4). These results are consistent with a retrieval-based account of JOLs, and demonstrate that the "delayed-JOL effect" can be obtained without a long delay.

Aging, working memory capacity and the proactive control of recollection: An event-related potential study

The present study investigated the role of working memory capacity (WMC) in the control of recollection in young and older adults. We used electroencephalographic event-related potentials (ERPs) to examine the effects of age and of individual differences in WMC on the ability to prioritize recollection according to current goals. Targets in a recognition exclusion task were words encoded using two alternative decisions. The left parietal ERP old/new effect was used as an electrophysiological index of recollection, and the selectivity of recollection measured in terms of the difference in its magnitude according to whether recognized items were targets or non-targets. Young adults with higher WMC showed greater recollection selectivity than those with lower WMC, while older adults showed nonselective recollection which did not vary with WMC. The data suggest that aging impairs the ability to engage cognitive control effectively to prioritize what will be recollected.