Individual differences in working memory capacity predict visual attention allocation

To the extent that individual differences in working memory capacity (WMC) reflect differences in attention (Baddeley, 1993; Engle, Kane, & Tuholski, 1999), differences in WMC should predict performance on visual attention tasks. Individuals who scored in the upper and lower quartiles on the OSPAN working memory test performed a modification of Egly and Homa’s (1984) selective attention task. In this task, the participants identified a central letter and localized a displaced letter flashed somewhere on one of three concentric rings. When the displaced letter occurred closer to fixation than the cue implied, high-WMC, but not low-WMC, individuals showed a cost in the letter localization task. This suggests that low-WMC participants allocated attention as a spotlight, whereas those with high WMC showed flexible allocation.     

Individual differences in working memory capacity and enumeration

Two experiments are reported in which subjects performed working memory and enumeration tasks. In the first experiment, subjects scoring low on the working memory task also performed poorly on the attention-demanding "counting" portion of the enumeration task. Yet no span differences were found for the non-attention-demanding "subitizing" portion. In Experiment 2, conjunctive and disjunctive distractors were added to the enumeration task. Although both high and low working memory span subjects were adversely affected by the addition of conjunctive distractors, the effect was much greater for the low-span subjects. Implications from these findings are that differences in working memory capacity correspond to differences in capability for controlled attention.     

Individual differences in working memory capacity and search efficiency

In two experiments, we examined how various learning conditions impact the relation between working memory capacity (WMC) and memory search abilities. Experiment 1 employed a delayed free recall task with semantically related words to induce the buildup of proactive interference (PI) and revealed that the buildup of PI differentially impacted recall accuracy and recall latency for low-WMC and high-WMC individuals. Namely, the buildup of PI impaired recall accuracy and slowed recall latency for low-WMC individuals to a greater extent than what was observed for high-WMC individuals. To provide a circumstance in which previously learned information remains relevant over the course of learning, Experiment 2 required participants to complete a multitrial delayed free recall task with unrelated words. Results revealed that with increased practice with the same word list, WMC-related differences were eventually eliminated in interresponse times (IRTs) and recall accuracy, but not recall latency. Thus, despite still accumulating larger search sets, low-WMC individuals searched LTM as efficiently as high-WMC individuals. Collectively, these results are consistent with the notion that under normal free recall conditions, low-WMC individuals search LTM less efficiently than do high-WMC individuals because of their reliance on noisy temporal–contextual cues at retrieval. However, it appears that under conditions in which previously learned items remain relevant at recall, this tendency to rely on vague self-generated retrieval cues can actually facilitate the ability to accurately and quickly recall information.     

Individual differences in working memory capacity predict sleep-dependent memory consolidation

Decades of research have established that "online" cognitive processes, which operate during conscious encoding and retrieval of information, contribute substantially to individual differences in memory. Furthermore, it is widely accepted that "offline" processes during sleep also contribute to memory performance. However, the question of whether individual differences in these two types of processes are related to one another remains unanswered. We investigated whether working memory capacity (WMC), a factor believed to contribute substantially to individual differences in online processing, was related to sleep-dependent declarative memory consolidation. Consistent with previous studies, memory for word pairs reliably improved after a period of sleep, whereas performance did not improve after an equal interval of wakefulness. More important, there was a significant, positive correlation between WMC and increase in memory performance after sleep but not after a period of wakefulness. The correlation between WMC and performance during initial test was not significant, suggesting that the relationship is specific to change in memory due to sleep. This suggests a fundamental underlying ability that may distinguish individuals with high memory capacity.     

Individual differences in working memory capacity predict retrieval-induced forgetting

Selectively retrieving a subset of previously studied information enhances memory for the retrieved information but causes forgetting of related, nonretrieved information. Such retrieval-induced forgetting (RIF) has often been attributed to inhibitory executive-control processes that supposedly suppress the nonretrieved items' memory representation. Here, we examined the role of working memory capacity (WMC) in young adults' RIF. WMC was assessed by means of the operation span task. Results revealed a positive relationship between WMC and RIF, with high-WMC individuals showing more RIF than low-WMC individuals. In contrast, individuals showed enhanced memory for retrieved information regardless of WMC. The results are consistent with previous individual-differences work that suggests a close link between WMC and inhibitory efficiency. In particular, the finding supports the inhibitory executive-control account of RIF.     

Sensation seeking and selective attention: focused and divided attention on a dichotic listening task.

Differences in selective attention as a function of sensation seeking, extraversion, neuroticism, and psychoticism were examined in 108 undergraduates using a dichotic listening task. Dependent measures included shadowing performance, reaction times to a secondary light task, target detection, and recall. The results suggested that high sensation seekers have better focused attention than low sensation seekers, and these effects were strongest on the 1st trials of the shadowing tasks. High sensation seekers did not attend differently than low sensation seekers to words related to their interests (sexual, violent, or drug related). Extraversion was associated with greater recall of these kinds of words, although there were no overall differences in selective attention as a function of Eysenck's dimensions. The role of arousal in personality and attention is discussed, particularly in regard to the response of sensation seekers to task novelty.     

Sex differences in dichotic listening

The present study quantified the magnitude of sex differences in perceptual asymmetries as measured with dichotic listening. This was achieved by means of a meta-analysis of the literature dating back from the initial use of dichotic listening as a measure of laterality. The meta-analysis included 249 effect sizes pertaining to sex differences and 246 effect sizes for the main effect of laterality. The results showed small and homogeneous sex differences in laterality in favor of men (d=0.054). The main effect of laterality was of medium magnitude (d=0.609) but it was heterogeneous. Homogeneity for the main effect of laterality was achieved through partitioning as a function of task, demonstrating larger asymmetries for verbal (d=0.65) than for non-verbal tasks (d=0.45). The results are discussed with reference to top-down and bottom-up factors in dichotic listening. The possible influence of a publication bias is also discussed.     

Individual differences in working memory capacity and dual-process theories of the mind

Dual-process theories of the mind are ubiquitous in psychology. A central principle of these theories is that behavior is determined by the interplay of automatic and controlled processing. In this article, the authors examine individual differences in the capacity to control attention as a major contributor to differences in working memory capacity (WMC). The authors discuss the enormous implications of this individual difference for a host of dual-process theories in social, personality, cognitive, and clinical psychology. In addition, the authors propose several new areas of investigation that derive directly from applying the concept of WMC to dual-process theories of the mind.     

Focused and divided attention to dichotic wordstreams

Two dichotic wordstreams both containing meaningful word relations (synonyms) were presented under two different task requirements. When asked to attend to both channels, the majority of the subjects (8 out of 10) was able to pick up the synonyms in both wordstreams but, in the case of simultaneous (double) synonym occurence, dual performance became worse. The outcomes of the focused attention task corroborated the multi-channel input processing idea: synonyms on the to-be-rejected channel retarded, in particular, the identification of the synonyms on the to-be- attended channel. Consistent with the selective attention literature, although functioning in a suboptimal way, filter setting appears to work better when the subject is confronted with a longer string of words to which he must attend.     

Individual differences in working memory capacity predict action monitoring and the error-related negativity

Neuroscience suggests that the anterior cingulate cortex (ACC) is responsible for conflict monitoring and the detection of errors in cognitive tasks, thereby contributing to the implementation of attentional control. Though individual differences in frontally mediated goal maintenance have clearly been shown to influence outward behavior in interference-rich contexts, it is unclear whether corresponding differences exist in neural responses that arise out of the ACC. To investigate this possibility, we conducted an electrophysiological study using a variant of the Simon Task, recording event-related potentials (ERPs) in healthy normal individuals with varying working memory capacity (high vs. low spans; a behavioral proxy for variability in goal maintenance). Primary analyses focused on the magnitude of the error-related negativity (ERN), a response-locked ERP component associated with the commission of errors thought to arise because of action monitoring in the ACC. Our results revealed that frontally mediated working memory capacity may alter error monitoring by the ACC, with high spans showing a greater ERN than low spans. These individual differences were also observed in the posterror positivity, a response-locked ERP component associated with updating cognitive strategies, suggesting greater awareness of errors with increased working memory capacity. These results are interpreted within 2-process models of attentional control, suggesting individuals with greater working memory capacity may better maintain task goals by more strongly biasing neural activity in frontal-executive networks.     

Individual working memory capacity is uniquely correlated with feature-based attention when combined with spatial attention

A growing literature suggests that working memory and attention are closely related constructs. Both involve the selection of task-relevant information, and both are characterized by capacity limits. Furthermore, studies using a variety of methodological approaches have demonstrated convergent working memory and attention-related processing at the individual, neural and behavioral level. Given the varieties of both constructs, the specific kinds of attention and WM must be considered. We find that individuals' working memory capacity (WMC) uniquely interacts with feature-based attention when combined with spatial attention in a cuing paradigm (Posner, 1980). Our findings suggest a positive correlation between WM and feature-based attention only within the spotlight of spatial attention. This finding lends support to the controlled attention view of working memory by demonstrating that integrated feature-based expectancies are uniquely correlated with individual performance on a working memory task.     

Individual differences in working memory capacity and resistance to belief bias in syllogistic reasoning

In two experiments, we investigated the possibility that individual differences in working memory capacity (WMC) would provide resistance to belief bias in syllogistic reasoning. In Experiment 1 (N?=?157), participants showed a belief bias effect in that they had longer response times and decreased accuracy on syllogisms with conflict between the validity and believability of the conclusion than on syllogisms with no such conflict. However, this effect did not differ as a function of individual differences in WMC. Experiment 2 (N?=?122) replicated this effect with the addition of decontextualized (i.e., nonsense) syllogisms as a different means of measuring the magnitude of the belief bias effect. Although individual differences in WMC and fluid intelligence were related to better reasoning overall, the magnitude of the belief bias effect was not smaller for participants with greater WMC. The present study offers two novel findings: (a) The belief bias effect is independent of individual differences in WMC and fluid intelligence, and (b) resolving conflict in verbal reasoning is not a type of conflict resolution that correlates with individual differences in WMC, further establishing boundary conditions for the role of WMC in human cognitive processes.     

Verbatim and gist memory and individual differences in inhibition,sustained attention,and working memory capacity

In the present study, we explored whether individual differences in inhibition, sustained attention, and working memory capacity (WMC) are related to false memory task performance. We defined the processes in such a task according to the fuzzy trace theory and used multinomial modelling methodology to measure the contribution of these latent processes. We found higher verbatim memory in participants with a high WMC, as measured by the Rotation Span task, and in individuals who committed more errors in the Sustained Attention Response Task (SART). Participants with a high WMC and low-error level in SART showed higher gist memory for targets, and individuals high in WMC also rejected orthographically related distractors more effectively due to the recollection of distractors’ corresponding targets. We also observed that participants with better inhibition control were more conservative in guessing that an item was old.     

Individual differences in working memory capacity affect false memories for missing aspects of events

Recently, Gerrie, Belcher, and Garry (2006) found that, when participants watch an event with parts missing, they falsely claim to have seen the missing parts--but they were more likely to claim they had seen less crucial parts than more crucial parts. Their results fit with a source-monitoring framework (SMF; Johnson, Hashtroudi, & Lindsay, 1993) explanation of false memories. In this paper we used individual differences in working memory capacity (WMC) to examine the SMF explanation of false memories for missing aspects of events. An accumulating body of research suggests that WMC is strongly related to controlling attention, including the ability to distinguish between sources of information. The primary purpose of the present study was to examine whether people with larger WMC are better able to ward off false memories for missing information than those with a smaller WMC. We showed that higher WMC reduced false recognition of crucial information, but did not change false recognition of noncrucial information. Additionally, we found that WMC had little effect on participants' subjective experience of true and false recognition of events, regardless whether the information was crucial or not. These results provide further evidence that people's WMC is related to their source-monitoring ability.     

Individual capacity differences predict working memory performance and prefrontal activity following dopamine receptor stimulation

Dopamine receptors are abundant in the prefrontal cortex (PFC), a critical region involved in working memory. This pharmacological fMRI study tested the relationships between dopamine, PFC function, and individual differences in working memory capacity. Subjects performed a verbal delayed-recognition task after taking either the dopamine receptor agonist bromocriptine or a placebo. Behavioral effects of bromocriptine treatment depended on subjects’ working memory spans, with the greatest behavioral benefit for lower span subjects. After bromocriptine, PFC activity was positively correlated with a measure of cognitive efficiency (RT slope) during the probe period of the task. Less efficient subjects with slower memory retrieval rates had greater PFC activity, whereas more efficient subjects had less activity. After placebo, these measures were uncorrelated. These results support the role of dopamine in verbal working memory and suggest that dopamine may modulate the efficiency of retrieval of items from the contents of working memory. Individual differences in PFC dopamine receptor concentration may thus underlie the behavioral effects of dopamine stimulation on working memory function.     

Individual differences in working memory capacity affect false memories for missing aspects of events

Recently, Gerrie, Belcher, and Garry (2006) found that, when participants watch an event with parts missing, they falsely claim to have seen the missing parts—but they were more likely to claim they had seen less crucial parts than more crucial parts. Their results fit with a source-monitoring framework (SMF; Johnson, Hashtroudi, & Lindsay, 1993) explanation of false memories. In this paper we used individual differences in working memory capacity (WMC) to examine the SMF explanation of false memories for missing aspects of events. An accumulating body of research suggests that WMC is strongly related to controlling attention, including the ability to distinguish between sources of information. The primary purpose of the present study was to examine whether people with larger WMC are better able to ward off false memories for missing information than those with a smaller WMC. We showed that higher WMC reduced false recognition of crucial information, but did not change false recognition of noncrucial information. Additionally, we found that WMC had little effect on participants’ subjective experience of true and false recognition of events, regardless whether the information was crucial or not. These results provide further evidence that people's WMC is related to their source-monitoring ability.     

The role of working memory capacity in autobiographical retrieval: Individual differences in strategic search

Remembering previous experiences from one's personal past is a principal component of psychological well-being, personality, sense of self, decision making, and planning for the future. In the current study the ability to search for autobiographical information in memory was examined by having college students recall their Facebook friends. Individual differences in working memory capacity manifested itself in the search of autobiographical memory by way of the total number of friends remembered, the number of clusters of friends, size of clusters, and the speed with which participants could output their friends' names. Although working memory capacity was related to the ability to search autobiographical memory, participants did not differ in the manner in which they approached the search and used contextual cues to help query their memories. These results corroborate recent theorising, which suggests that working memory is a necessary component of self-generating contextual cues to strategically search memory for autobiographical information.