Age, memory load, and individual differences in working memory as determinants of class-inclusion reasoning.

We studied the effects of individual differences in speak-span scores and variations in memory demands on the class-inclusion performance of 10-, 13-, and 15-year-old children. The speak-span task was an age-appropriate modification of Daneman and Carpenter's (1980) reading-span task and was considered to be a measure of global resources. The age variable was assumed to be a global index of skill development, and some of the specific skills hypothesized to be important in class-inclusion reasoning were estimated using a mathematical model. The results from both regression analyses and the mathematical model indicated that differences in age, speak span, and memory load all affected performance. Surprisingly, the effects of speak span and memory load were independent. However, the effects of each of these variables depended on the age level of the participants. Based on these findings, we argued that (a) resources vary continuously with age, (b) both skill level and global resources should be varied in developmental studies of problem solving, and (c) resource theories (e.g., Norman & Shallice, 1986) should be modified to account for developmental change.     

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 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 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 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.     

Individual differences in the gesture effect on working memory

Co-speech gestures have been shown to interact with working memory (WM). However, no study has investigated whether there are individual differences in the effect of gestures on WM. Combining a novel gesture/no-gesture task and an operation span task, we examined the differences in WM accuracy between individuals who gestured and individuals who did not gesture in relation to their WM capacity. Our results showed individual differences in the gesture effect on WM. Specifically, only individuals with low WM capacity showed a reduced WM accuracy when they did not gesture. Individuals with low WM capacity who did gesture, as well as high-capacity individuals (irrespective of whether they gestured or not), did not show the effect. Our findings show that the interaction between co-speech gestures and WM is affected by an individual’s WM load.     

Individual differences in proactive interference in verbal and visuospatial working memory

Proactive interference (PI) has been shown to affect working memory (WM) span as well as the predictive utility of WM span measures. However, most of the research on PI has been conducted using verbal memory items, and much less is known about the role of PI in the visuospatial domain. In order to further explore this issue, the present study used a within-subjects manipulation of PI that alternated clusters of trials with verbal and visuospatial to-be-remembered items. Although PI was shown to build and release across trials similarly in the two domains, important differences also were observed. The ability of verbal WM to predict performance on a measure of fluid intelligence was significantly affected by the amount of PI present, consistent with past research, but this proved not to be the case for visuospatial WM. Further, individuals’ susceptibility to PI in one domain was relatively independent of their susceptibility in the other domain, suggesting that, contrary to some theories of executive function, individual differences in PI susceptibility may not be domain-general.     

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 strategies for reading expository text

This study investigated whether individual differences in working memory (WM) span are associated with different WM management strategies during the reading of expository text. In Experiment 1, probe questions were presented on line during reading to determine whether thematic information was maintained in WM throughout comprehension. The data indicated that readers across the range of WM span maintained thematic information in WM throughout the reading of a given passage. In Experiment 2, sentence reading times and accuracy for both topic and detail questions were measured in two conditions: when topic sentences were present and when topic sentences were absent. Subjects performed similarly across the range of WM span in the topic-present condition, but lower span subjects performed more poorly on detail questions in the topic-absent condition. In Experiment 3, the topic-present condition of the second experiment was replicated, except that subjects expected to receive questions about details only. Thematic processing and retention of topic and detail information all increased with span. Taken together, these results suggest that, for more difficult text processing tasks, high- and low-span subjects adopt different WM management strategies and these strategies influence what is learned from reading the text.     

Individual and developmental differences in working memory across the life span

The effects of secondary tasks on verbal and spatial working memory were examined in multiple child, young adult, and older adult samples. Although memory span increased with age in the child samples and decreased with age in the adult samples, there was little evidence of systematic change in the magnitude of interference effects. Surprisingly, individuals who had larger memory spans when there was no secondary task showed greater interference effects than their age-mates. These findings are inconsistent with the hypothesis that age and individual differences in working memory are due to differences in the ability to inhibit irrelevant information, at least as this hypothesis is currently formulated. Moreover, our results suggest that different mechanisms underlie developmental and individual differences in susceptibility to interference across the life span. A model is proposed in which memory span and processing speed both increase with development but are relatively independent abilities within age groups.     

Individual differences in cognition: Some relationships between personality and memory

Individual differences in cognition were studied in the form of the hypothesis that arousal, as indexed by personality measures of extraversion and neuroticism, affects the way in which verbal material is organized in memory. Subjects pretested on measures of these personality variables participated in either a paired-associates learning or a free-recall experiment. On the paired-associates task, subjects who were thought to be high on arousal made fewer errors when response terms were semantically similar than low arousal subjects. On the other hand, subjects thought low on arousal made fewer errors when response words were phonetically similar than high arousal subjects. On the free-recall task, low arousal subjects were found to cluster words together on the basis of semantic category at a higher rate than high arousal subjects. These results were taken to support the view that high arousal (as indexed by personality measures) leads to a focus on the physical aspects of verbal material, whereas low arousal leads to a memory organized around semantic aspects. The implications of these findings for other views of memory are discussed.     

Individual differences in working memory capacity and divided attention in dichotic listening

The controlled attention theory of working memory suggests that individuals with greater working memory capacity (WMC) are better able to control or focus their attention than individuals with lesser WMC. This relationship has been observed in a number of selective attention paradigms including a dichotic listening task (Conway, Cowan, & Bunting, 2001) in which participants were required to shadow words presented to one ear and ignore words presented to the other ear. Conway et al. found that when the participant’s name was presented to the ignored ear, 65% of participants with low WMC reported hearing their name, compared to only 20% of participants with high WMC, suggesting greater selective attention on the part of high WMC participants. In the present study, individual differences in divided attention were examined in a dichotic listening task, in which participants shadowed one message and listened for their own name in the other message. Here we find that 66.7% of high WMC and 34.5% of low WMC participants detected their name. These results suggest that as WMC capacity increases, so does the ability to control the focus of attention, with high WMC participants being able to flexibly “zoom in” or “zoom out” depending on task demands.     

Individual differences in cognitive style,working memory,and semantic integration

In two experiments subjects classified as being either high or low in field articulation (FA) performed a semantic integration task with high-information load. In Experiment 1, differences in performance between high- and low-FA subjects on an inference and recognition test were obtained when sentences were presented for 5 sec a piece but not when they were presented for 10 sec a piece. In Experiment 2, performance differences between high and low-FA subjects were eliminated by presenting only a specific subset of the sentences for 10 sec a piece. The implications of these results for explanations of FA effects in semantic integration are 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.     

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 differences in working memory: introduction to the special section.

This special section includes a set of 5 articles that examine the nature of inter- and intraindividual differences in working memory, using working memory span tasks as the main research tools. These span tasks are different from traditional short-term memory spans (e.g., digit or word span) in that they require participants to maintain some target memory items (e.g., words) while simultaneously performing some other tasks (e.g., reading sentences). In this introduction, a brief discussion of these working memory span tasks and their characteristics is provided first. This is followed by an overview of 2 major theoretical issues that are addressed by the subsequent articles--(a) the factors influencing the inter- and intraindividual differences in working memory performance and (b) the domain generality versus domain specificity of working memory--and also of some important issues that must be kept in mind when readers try to evaluate the claims regarding these 2 theoretical issues.     

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.     

Individual differences in sentence memory

Results from an experiment with two parts are presented in this paper. In part one, participants listened to sentences containing two, three, four, or five clauses, and were asked questions about the content of the sentences. The results of part one demonstrate that an important unit of representation in sentence memory is the clause, and not some other component of discourse structure. In part two, the same group of participants performed eight different short-term storage/working memory tasks. A composite complex span score was computed for each participant based on three working memory tasks closely based on Daneman & Carpenter's (1980) reading span task. This working memory measure was significantly correlated with the participants' performance on the sentence memory task in part one. A second working memory measure—N-back—was also significantly correlated with the participants' performance on the sentence memory task, and there was no correlation between their performance on the complex span task and the N-back task. It is therefore concluded that (i) working memory consists of a number of dissociable components; and (ii) memory for sentences taps into more than one of these working memory components. Furthermore, the high correlations of sentence memory with the complex span and the N-back tasks (neither of which are language processing tasks) suggests that memory for sentences is not simply a result of linguistic experience; rather, it is likely that an independent working memory component contributes to participants' performance on the sentence memory task.     

Individual differences in working memory and comprehension: a test of four hypotheses.

A relationship has consistently been found between measures of working memory and reading comprehension. Four hypotheses for this relationship were tested in 3 experiments. In the first 2 experiments, a moving window procedure was used to present the operation-word and reading span tasks. High- and low-span subjects did not differentially trade off time on the elements of the tasks and the to-be-remembered word. Furthermore, the correlation between span and comprehension was undiminished when the viewing times were partialed out. Experiment 3 compared a traditional experimenter-paced simple word-span and a subject-paced span in their relationship with comprehension. The experimenter-paced word-span correlated with comprehension but the subject-paced span did not. The results of all 3 experiments support a general capacity explanation for the relationship between working memory and comprehension.