Beyond resources: Formal models of complexity effects and age differences in working memory

Distinct age-related brain activity patterns in the prefrontal cortex when increasing cognitive load: A functional near-infrared spectroscopy study

Researchers have long observed distinct brain activity patterns in older adults compared with younger adults that correlate with cognitive performance. Mainly, older adults tend to show over-recruitment of bilateral brain regions during lower task loads and improved performance interpreted as compensation, but not observed at higher loads. However, there are discrepancies about whether increases in activity are compensatory and whether older adults can show compensation at higher loads. Our aim was to examine age-related differences in prefrontal cortex (PFC) activity and cognitive performance using functional near-infrared spectroscopy (fNIRS) during single and dual N-back tasks. Twenty-seven young adults (18-27 years) and 31 older adults (64-84 yrs) took part in the study. We used a robust fNIRS data methodology consisting of channel and region of interest analyses. Results showed differences in performance between task load conditions and age-related differences in reaction times but no age-group effects for accuracy. Older adults exhibited more bilateral PFC activation compared with young adults across all tasks and showed increases in brain activity in high compared to low load conditions. Our findings further support previous reports showing that older adults use compensatory recruitment of additional brain regions in PFC to maintain cognitive performance but go against the notion that such compensation is not present at higher cognitive loads. Additionally, our results indicate that fNIRS is a sensitive tool that can characterize adaptive cortical changes in healthy aging.

The Mediating Role of Affective States in Short-Term Effects of Activity Engagement on Working Memory in Older Age

INTRODUCTION

It has been shown that activity engagement is associated with cognitive ability in older age, but mechanisms behind the associations have rarely been examined. Following a recent study which showed short-term effects of activity engagement on working memory performance appearing 6 h later, this study examined the mediating role of affective states in this process.

METHODS

For 7 times per day over 2 weeks, 150 Swiss older adults (aged 65-91 years) reported their present (sociocognitive/passive leisure) activities and affective states (high-arousal positive, low-arousal positive, high-arousal negative, and low-arousal negative) and completed an ambulatory working memory task on a smartphone.

RESULTS

Multilevel vector autoregression models showed that passive leisure activities were associated with worse working memory performance 6 h later. Passive leisure activities were negatively associated with concurrent high-arousal positive affect (and high-arousal negative affect); high-arousal positive affect was negatively associated with working memory performance 6 h later. A Sobel test showed a significant mediation effect of high-arousal positive affect linking the time-lagged relationship between passive leisure activities and working memory. Additionally, sociocognitive activities were associated with better working memory performance 6 h later. Sociocognitive activities were associated with concurrent higher high- and low-arousal positive affect, which, however, were not associated with working memory performance 6 h later. Thus, a mediation related to sociocognitive activities was not found.

DISCUSSION

Passive leisure activities could influence working memory performance through high-arousal positive affect within a timeframe of several hours. Results are discussed in relation to an emotional, and possibly a neuroendocrine, pathway explaining the time-lagged effects of affective states on working memory performance.

Disentangling Processing and Storage Accounts of Working Memory Development in Childhood

Researchers have been asking the question of what drives the development of working memory (WM) during childhood for decades. This question is particularly challenging because so many aspects of cognition develop with age that it is difficult to disentangle them and find out which factors are causal or fundamental. In this review, we first prepare to discuss this issue by inquiring whether increases in storage, processing, or both are the fundamental driving factor(s) of the age-related increase in WM capability in childhood. We contend that by experimentally manipulating either factor and observing changes in the other, it is possible to learn about causal roles in WM development. We discuss research on school-aged children that seems to suggest, by means of such an approach, that the growth of storage is causal for some phases or steps in WM tasks, but that the growth of processing is causal for other steps. In our theoretical proposal, storage capacity of the focus of attention determines earlier steps of information processing by constraining the selective encoding of information into WM, whereas processing dependent on the focus of attention determines later steps, like the detection of patterns that can simplify the effective memory load and adoption of a proactive stance of maintenance in dual-task settings. Future directions for research are discussed.

The contribution of episodic long-term memory to working memory for bindings

The present experiments support two conclusions about the capacity limit of working memory (WM). First, they provide evidence for the Binding Hypothesis, WM capacity is limited by interference between bindings but not items. Second, they show that episodic LTM contributes substantially to binding memory when the capacity of WM is stretched to the limit by larger set sizes. We tested immediate memory for sets of word-picture pairs. With increasing set size, memory for bindings declined more precipitously than memory for items, as predicted from the binding hypothesis. Yet, at higher set sizes performance was more stable than expected from a capacity limited memory, suggesting a contribution of episodic long-term memory (LTM) to circumvent the WM capacity limit. In support of that hypothesis, we show a double dissociation of contributions of WM and episodic LTM to binding memory: Performance at set sizes larger than 3 was specifically affected by proactive interference - but were immune to influences from a distractor-filled delay. In contrast, performance at set size 2 was unaffected by proactive interference but harmed by a distractor-filled delay.

Charting everyday activities in later life: Study protocol of the mobility, activity, and social interactions study (MOASIS)

Prominent theories of aging emphasize the importance of resource allocation processes as a means to maintain functional ability, well-being and quality of life. Little is known about which activities and what activity patterns actually characterize the daily lives of healthy older adults in key domains of functioning, including the spatial, physical, social, and cognitive domains. This study aims to gain a comprehensive understanding of daily activities of community-dwelling older adults over an extended period of time and across a diverse range of activity domains, and to examine associations between daily activities, health and well-being at the within- and between-person levels. It also aims to examine contextual correlates of the relations between daily activities, health, and well-being. At its core, this ambulatory assessment (AA) study with a sample of 150 community-dwelling older adults aged 65 to 91 years measured spatial, physical, social, and cognitive activities across 30 days using a custom-built mobile sensor ("uTrail"), including GPS, accelerometer, and audio recording. In addition, during the first 15 days, self-reports of daily activities, psychological correlates, contexts, and cognitive performance in an ambulatory working memory task were assessed 7 times per day using smartphones. Surrounding the ambulatory assessment period, participants completed an initial baseline assessment including a telephone survey, web-based questionnaires, and a laboratory-based cognitive and physical testing session. They also participated in an intermediate laboratory session in the laboratory at half-time of the 30-day ambulatory assessment period, and finally returned to the laboratory for a posttest assessment. In sum, this is the first study which combines multi-domain activity sensing and self-report ambulatory assessment methods to observe daily life activities as indicators of functional ability in healthy older adults unfolding over an extended period (i.e., 1 month). It offers a unique opportunity to describe and understand the diverse individual real-life functional ability profiles characterizing later life.

Involvement of executive control in neural capacity related to working memory in aging: an ERP P300 study

Executive control could be involved in neural capacity, which corresponds to the modulation of neural activity with increased task difficulty. Thus, by exploring the P300-an electrophysiological correlate of working memory-we examined the role played by executive control in both the age-related decline in working memory and neural capacity in aging. Event-related potentials (ERPs) were recorded while younger and older participants performed a Sternberg task with two set sizes (2 vs. 6 items), allowing us to calculate a neural capacity index. Participants also completed two control tasks (Stroop and 3-back tests), which were used to calculate a composite executive control index. Results indicated that working memory performance decreased with aging and difficulty. At the neural level, results indicated that the P300 amplitude varied with aging and also with task difficulty. In the low difficulty condition, frontal P300 amplitude was higher for older than for younger adults, whereas in the high difficulty condition, the amplitude of frontal and parietal P300 did not differ between both age groups. Results also suggest that task difficulty led to a decrease in parietal amplitude in both age groups and to an increase in frontal amplitude in younger but not older adults. Both executive control and frontal neural capacity mediated the age-related variance in working memory for older adults. Moreover, executive control mediated the age-related variance in the frontal neural capacity of older adults. Thus, the present study suggests a model for older adults in which executive control deficits with advancing age lead to less efficient frontal recruitment to cope with task difficulty (neural capacity), which in turn has a negative impact on working memory functioning.

Chunking in Visual Working Memory: Are Visual Features of Real-World Objects Stored in Chunks?

Are visual features of real-world objects stored as bound units? Previous research has shown that simple visual features (e.g., colored squares or geometric shapes) can be effectively bound together when forming predictable pairs in memory tasks. Through a "memory compression" process, observers can take advantage of these features to compress them into a chunk. However, a recent study found that visual features in real-world objects are stored independently. In the present study, we explored this issue by using drawings of fruits as memory stimuli, presenting four pictures of fruit in separate test trials in which we required observers to remember eight total features (i.e., four colors and four shapes). In the congruent trials, the color of the fruit matched its natural appearance (e.g., a red apple), while in incongruent trials, the color of the fruit mismatched its natural appearance (e.g., a red banana). We paired the shape of the fruits randomly with a color (without replacement). According to chunking theory, if visual features of real-world objects are stored in a chunk, the highest memory capacity should be accompanied by the longest response time in congruent trials due to an extra decoding process required from the chunk. We did find that participants had the highest memory capacity in the congruent condition, but their response times in the congruent condition were significantly faster than in the incongruent condition. Thus, observers did not undergo a decoding process in the congruent condition, and we concluded that visual features in real-world objects are not stored in a chunk.

Aging and feature binding in visual working memory

Older adults have reduced performance in visual working memory tasks in comparison to young adults, but the precipitators of the age-related impairment are not fully understood. The most common interpretation of this difference is that older adults are incapable of maintaining the same amount of object representations as young adults over short intervals (in line with the fixed-slot model of working memory). However, it has remained largely unexplored whether the age-related decline is only due to the number of representations that older individuals can retain in visual working memory, or whether the content of the representation(s) may have an effect as well (in line with the flexible-resource model of working memory). Feature binding studies represent an interesting research line to examine the content of older adults' representations. In this mini-review, we present the main results across feature binding studies in aging, as well as highlight the importance of manipulating both the representation content and number to have a stress test of the various models of working memory and their contribution to aging. Overall, feature binding studies, together with the simultaneous manipulation of set size, will allow us to better understand the nature of the age-related decline of visual working memory.

Retest effects in working memory capacity tests: A meta-analysis

The repeated administration of working memory capacity tests is common in clinical and research settings. For cognitive ability tests and different neuropsychological tests, meta-analyses have shown that they are prone to retest effects, which have to be accounted for when interpreting retest scores. Using a multilevel approach, this meta-analysis aims at showing the reproducibility of retest effects in working memory capacity tests for up to seven test administrations, and examines the impact of the length of the test-retest interval, test modality, equivalence of test forms and participant age on the size of retest effects. Furthermore, it is assessed whether the size of retest effects depends on the test paradigm. An extensive literature search revealed 234 effect sizes from 95 samples and 68 studies, in which healthy participants between 12 and 70 years repeatedly performed a working memory capacity test. Results yield a weighted average of g = 0.28 for retest effects from the first to the second test administration, and a significant increase in effect sizes was observed up to the fourth test administration. The length of the test-retest interval and publication year were found to moderate the size of retest effects. Retest effects differed between the paradigms of working memory capacity tests. These findings call for the development and use of appropriate experimental or statistical methods to address retest effects in working memory capacity tests.

Are stronger memories forgotten more slowly? No evidence that memory strength influences the rate of forgetting

Information stored in visual short-term memory is used ubiquitously in daily life; however, it is forgotten rapidly within seconds. When more items are to be remembered, they are forgotten faster, potentially suggesting that stronger memories are forgotten less rapidly. Here we tested this prediction with three experiments that assessed the influence of memory strength on the rate of forgetting of visual information without manipulating the number of items. Forgetting rate was assessed by comparing the accuracy of reports in a delayed-estimation task following relatively short and long retention intervals. In the first experiment, we compared the forgetting rate of items that were directly fixated, to items that were not. In Experiments 2 and 3 we manipulated memory strength by extending the exposure time of one item in the memory array. As expected, direct fixation and longer exposure led to better accuracy of reports, reflecting stronger memory. However, in all three experiments, we did not find evidence that increased memory strength moderated the forgetting rate.

Working Memory Period: The Endurance of Mental Representations

Working memory span assesses the maximum number of items that can be remembered in the face of concurrent processing. Models of working memory differ on several dimensions, yet many rely exclusively on this span procedure for their evidence. Three experiments consider an alternative paradigm that attempts to capture the endurance limits for remembering a fixed number of items during concurrent processing. Eight-year-old children performed two versions of this working memory period measure—operation period and reading period. Period scores show healthy test–retest reliability and external validity for scholastic attainment, comparing well with span scores in these respects. In addition, period is highly correlated with span and shows similar effects of varying the order in which stimuli are presented. We conclude that the durability of representations is an important factor in both span and period.

The Effects of Aging on the Components of Auditory - Verbal Short-Term Memory

This study aimed at exploring the effects of aging on the multiple components of the auditory-verbal short-term memory (STM). Participants of 45-54, 55-64, 65-74 and 75-84 years of age were presented STM tasks assessing short-term retention of order and item information, and of phonological and lexical-semantic information separately. Because older participants often present reduced hearing levels, we sought to control for an effect of hearing status on performance on STM tasks. Participants' hearing thresholds were measured with a pure-tone audiometer. The results showed age-related effects on all STM components. However, after hearing status was controlled for in analyses of covariance, the age-related differences became non-significant for all STM processes. The fact that age-related hearing loss may in large part explain decreases in performance on STM tasks with aging is discussed.

Updating the emotional content of working memory in social anxiety

BACKGROUND AND OBJECTIVES

Cognitive accounts suggest that information processing biases have an important role in the etiology and maintenance of social anxiety (SA). Empirical evidence support this notion has been established in variety of cognitive domains. Yet, it is still not known how social anxious individuals process emotional content in working memory (WM). Maladaptive WM updating may influence emotion regulation and anxiety during social situations in SA. Thus, the aim of the present study was to explore biases when updating emotional content in SA.

METHODS

31 participants with high SA and 34 control participants performed an emotional 2-back task. Biases were assessed by intrusion cost in reaction times, which reflects the conflict between the inhibition of irrelevant content and the activation of relevant content.

RESULTS

Results revealed a diminished intrusion cost in reaction times for irrelevant positive content in the high, but not in the low SA group. No differences were found for negative or neutral content.

LIMITATIONS

In the present study we used an analogue sample of students with high SA rather than a true clinical sample. Further research is needed to examine WM updating in clinical population.

CONCLUSIONS

These findings suggest that individuals with SA are better at inhibiting irrelevant positive information, a maladaptive cognitive bias that may prevent positive feedback from entering the cognitive system. This cognitive bias in WM may play a role in the etiology and maintenance of SA.

An interference account of the missing-VP effect

Sentences with doubly center-embedded relative clauses in which a verb phrase (VP) is missing are sometimes perceived as grammatical, thus giving rise to an illusion of grammaticality. In this paper, we provide a new account of why missing-VP sentences, which are both complex and ungrammatical, lead to an illusion of grammaticality, the so-called missing-VP effect. We propose that the missing-VP effect in particular, and processing difficulties with multiply center-embedded clauses more generally, are best understood as resulting from interference during cue-based retrieval. When processing a sentence with double center-embedding, a retrieval error due to interference can cause the verb of an embedded clause to be erroneously attached into a higher clause. This can lead to an illusion of grammaticality in the case of missing-VP sentences and to processing complexity in the case of complete sentences with double center-embedding. Evidence for an interference account of the missing-VP effect comes from experiments that have investigated the missing-VP effect in German using a speeded grammaticality judgments procedure. We review this evidence and then present two new experiments that show that the missing-VP effect can be found in German also with less restricting procedures. One experiment was a questionnaire study which required grammaticality judgments from participants without imposing any time constraints. The second experiment used a self-paced reading procedure and did not require any judgments. Both experiments confirm the prior findings of missing-VP effects in German and also show that the missing-VP effect is subject to a primacy effect as known from the memory literature. Based on this evidence, we argue that an account of missing-VP effects in terms of interference during cue-based retrieval is superior to accounts in terms of limited memory resources or in terms of experience with embedded structures.

Cognitive aging and training: the role of instructional coherence and advance organizers

BACKGROUND/STUDY CONTEXT: This study investigates whether there is a need for age-specific computer-based instructional design. The authors examined the effect of two design principles, instructional coherence and advance organizers, on learning outcomes of older and younger adults. Instructional coherence refers to the idea that people learn more deeply when information not directly relevant to learning goals is removed from training. Advance organizers are organizing frameworks for intended training content.

METHODS

Participants consisted of younger and older adults (mean ages were 21.7 and 75.1, respectively). Younger adults were university students and older adults were recruited from various sources, including retirement homes, senior activity centers, and online communities. We used a 2 (young, old) × 2 (low coherence, high coherence) × 2 (no advance organizer, advance organizer) between-subjects design and analyzed data using a multivariate analysis of variance (MANOVA).

RESULTS

Analyses revealed that (1) older adults performed worse on learning outcome measures compared with younger adults; (2) instructional coherence significantly improved the learning performance of both older and younger adults (Hypothesis 1 supported); and (3) advanced organizers improved the performance of older adults but did not affect the performance of younger adults in transfer tasks (Hypothesis 4 supported).

CONCLUSION

The latter finding (that advance organizers had differential effects on older and younger adults) suggests that perhaps there is a need for age-specific instructional formats. Future researchers should further explore whether and how age affects the learning process by examining the effect of different design principles on learning outcomes of older and younger adults.

Working memory as a moderator of impulsivity and alcohol involvement: testing the cognitive-motivational theory of alcohol use with prospective and working memory updating data

Research consistently shows that individuals high in impulsivity are at increased risk for excessive alcohol use and alcohol-related problems including alcohol use disorders (AUDs). Recent theorizing posits that working memory (WM) ability might moderate this association, but extant studies have suffered from methodological shortcomings, particularly mischaracterizing WM as a single, unitary construct and using only cross-sectional designs. This paper reports two studies that attempted to replicate and extend previous investigations of the relationship between WM, impulsivity, and alcohol involvement using two independent samples. Study 1 used a large (N=489 at baseline), prospective cohort of college students at high and low risk for AUD to investigate interactions between WM capacity and impulsivity on cross-sectional and prospective alcohol involvement. Study 2 used a large (N=420), cross-sectional sample of participants in an alcohol challenge study to investigate similar interactions between WM updating and impulsivity on recent alcohol involvement. Whereas Study 1 found that WM capacity moderates the relationship between some measures of impulsivity and alcohol involvement, with effects prospectively predicting alcohol involvement for up to three years, Study 2 did not find similar moderation effects when using measures of WM updating. These findings highlight the multifaceted nature of WM, which is often overlooked in the alcohol and impulsivity literature.

Oscillatory multiplexing of neural population codes for interval timing and working memory

Interval timing and working memory are critical components of cognition that are supported by neural oscillations in prefrontal-striatal-hippocampal circuits. In this review, the properties of interval timing and working memory are explored in terms of behavioral, anatomical, pharmacological, and neurophysiological findings. We then describe the various neurobiological theories that have been developed to explain these cognitive processes - largely independent of each other. Following this, a coupled excitatory - inhibitory oscillation (EIO) model of temporal processing is proposed to address the shared oscillatory properties of interval timing and working memory. Using this integrative approach, we describe a hybrid model explaining how interval timing and working memory can originate from the same oscillatory processes, but differ in terms of which dimension of the neural oscillation is utilized for the extraction of item, temporal order, and duration information. This extension of the striatal beat-frequency (SBF) model of interval timing (Matell and Meck, 2000, 2004) is based on prefrontal-striatal-hippocampal circuit dynamics and has direct relevance to the pathophysiological distortions observed in time perception and working memory in a variety of psychiatric and neurological conditions.

The Role of Similarity in Updating Numerical Information in Working Memory: Decomposing the Numerical Distance Effect

The present study investigates the process of updating representations in working memory (WM) and how similarity between the information involved influences this process. In WM updating tasks, the similarity in terms of numerical distance between the number to be substituted and the new one facilitates the updating process. We aimed to disentangle the possible effect of two dimensions of similarity that may contribute to this numerical effect: numerical distance itself and common digits shared between the numbers involved. Three experiments were conducted in which different ranges of distances and the coincidence between the digits of the two numbers involved in updating were manipulated. Results showed that the two dimensions of similarity had an effect on updating times. The greater the similarity between the information maintained in memory and the new information that substituted it, the faster the updating. This is consistent both with the idea of distributed representations based on features, and with a selective updating process based on a feature overwriting mechanism. Thus, updating in WM can be understood as a selective substitution process influenced by similarity in which only certain parts of the representation stored in memory are changed.

The impact of aging and hearing status on verbal short-term memory

The aim of this study is to assess the impact of hearing status on age-related decrease in verbal short-term memory (STM) performance. This was done by administering a battery of verbal STM tasks to elderly and young adult participants matched for hearing thresholds, as well as to young normal-hearing control participants. The matching procedure allowed us to assess the importance of hearing loss as an explanatory factor of age-related STM decline. We observed that elderly participants and hearing-matched young participants showed equal levels of performance in all verbal STM tasks, and performed overall lower than the normal-hearing young control participants. This study provides evidence for recent theoretical accounts considering reduced hearing level as an important explanatory factor of poor auditory-verbal STM performance in older adults.

No evidence for feature overwriting in visual working memory

The effect of repeating features in a short-term memory task was tested in three experiments. Experiments 1 and 2 used a recognition paradigm. Participants encoded four serially presented objects and then decided whether a probe matched one of them with regard to all three features. In the control condition no feature was repeated; in the experimental condition features were repeated in two memory objects. Experiment 3 used a cued recall paradigm with the same list design. After list presentation one feature was used as a cue uniquely indicating one of the memory objects. Participants recalled the remaining two features of the probed object. Feature overwriting as one component of the interference model of Oberauer and Kliegl (2006) predicts worse performance in the experimental compared to the control condition. Results of all three experiments did not support this hypothesis. Recognition performances in Experiments 1 and 2 were not impaired by repeating features. Recall performance in Experiment 3 was better for repeated features, contrary to the predictions of feature overwriting. Predictions from feature overwriting for the shape of serial position curves were also not confirmed.

Temporal stability and representational distinctiveness: key functions of orthographic working memory

A primary goal of working memory research has been to understand the mechanisms that permit working memory systems to effectively maintain the identity and order of the elements held in memory for sufficient time as to allow for their selection and transfer to subsequent processing stages. Based on the performance of two individuals with acquired dysgraphia affecting orthographic working memory (WM; the graphemic buffer), we present evidence of two distinct and dissociable functions of orthographic WM. One function is responsible for maintaining the temporal stability of letters held in orthographic WM, while the other is responsible for maintaining their representational distinctiveness. The failure to maintain temporal stability and representational distinctiveness gives rise, respectively, to decay and interference effects that manifest themselves in distinctive error patterns, including distinct serial position effects. The findings we report have implications beyond our understanding of orthographic WM, as the need to maintain temporal stability and representational distinctiveness in WM is common across cognitive domains.

The distance effect in numerical memory-updating tasks

Two experiments examined the role of numerical distance in updating numerical information in working memory. In the first experiment, participants had to memorize a new number only when it was smaller than a previously memorized number. In the second experiment, updating was based on an external signal, which removed the need to perform any numerical comparison. In both experiments, distance between the memorized number and the new one was manipulated. The results showed that smaller distances between the new and the old information led to shorter updating times. This graded facilitation suggests that the process by which information is substituted in the focus of attention involves maintaining the shared features between the new and the old number activated and selecting other new features to be activated. Thus, the updating cost may be related to amount of new features to be activated in the focus of attention.

Interferenz im Arbeitsgedächtnis:Ein formales Modell

Zusammenfassung. Die Autoren stellen ein theoretisches Modell des Arbeitsgedächtnisses vor, das auf neuronalen Netzwerkmodellen beruht. Inhalte des Arbeitsgedächtnisses sind durch verteilte Muster neuronaler Aktivität repräsentiert. Bindungen zwischen Merkmalen eines Elements, und zwischen Inhaltselementen und ihren Kontexten, werden durch synchrones Feuern von Einheiten hergestellt. Daraus folgt das Prinzip der Interferenz durch Merkmalsüberschreibung als ein Faktor, der die Arbeitsgedächtniskapazität begrenzt. Erste Evidenz für dieses Prinzip liefern Experimente, in denen die Wiedergabe von Wörtern durch das Ausmaß an Phonemüberlappung mit Distraktoren manipuliert werden konnte. Eine mathematische Formulierung des Modells wird exemplarisch auf Zeit-Genauigkeits-Funktionen von jungen und alten Erwachsenen bei einer arithmetischen Arbeitsgedächtnisaufgabe angewandt. Diese Anwendung illustriert die Möglichkeit, mithilfe von nicht-linearen Mehrebenen-Regressionsmodellen (NLME-Modellen) theoretisch gehaltvolle Modelle simultan auf Gruppenmittelwerte und interindividuelle Unterschiede anzuwenden.

Are there age differences in the executive component of working memory? Evidence from domain-general interference effects

Young and older adults performed verbal and spatial storage-only and storage-plus-processing working memory tasks while performing a secondary finger tapping task, and the effects on both the maximum capacity (measured as the longest series correct) and the reliability (measured as the proportion of items correct) of working memory were assessed. Tapping tended to produce greater disruption of working memory tasks that place greater demands on executive processes (i.e., storage-plus-processing tasks compared to storage-only span tasks). Moreover, tapping produced domain-general interference, disrupting both verbal and spatial working memory, providing further support for the idea that tapping interferes with the executive component of the working memory system, rather than domain-specific maintenance processes. Nevertheless, tapping generally produced equivalent interference effects in young and older adults. Taken together, these findings are inconsistent with the hypothesis that age-related declines in working memory are primarily attributable to a deficit in the executive component.

Differential age effects in load-dependent memory processing

This study examined differential age effects in a young and a middle-aged sample by means of a sequential n-back task with increasing memory load. Participants processed two streams of stimuli either separately as a single task, or simultaneously as a dual task. We investigated age effects as a function of memory load in both the single and the dual-task version. In accuracy, we observed differential age effects as a function of load, which were more prominent in the dual-compared to the single-task versions. That is, middle-aged participants performed poorer than young adults in the dual-task conditions, suggesting that early age-related changes become especially apparent in conditions where task coordination and resource sharing come into play. Regarding latencies, we observed no differential age effect, which we believe is due to characteristics of the sequential n-back task.

Common and unique components of inhibition and working memory: an fMRI, within-subjects investigation

Behavioural findings indicate that the core executive functions of inhibition and working memory are closely linked, and neuroimaging studies indicate overlap between their neural correlates. There has not, however, been a comprehensive study, including several inhibition tasks and several working memory tasks, performed by the same subjects. In the present study, 11 healthy adult subjects completed separate blocks of 3 inhibition tasks (a stop task, a go/no-go task and a flanker task), and 2 working memory tasks (one spatial and one verbal). Activation common to all 5 tasks was identified in the right inferior frontal gyrus, and, at a lower threshold, also the right middle frontal gyrus and right parietal regions (BA 40 and BA 7). Left inferior frontal regions of interest (ROIs) showed a significant conjunction between all tasks except the flanker task. The present study could not pinpoint the specific function of each common region, but the parietal region identified here has previously been consistently related to working memory storage and the right inferior frontal gyrus has been associated with inhibition in both lesion and imaging studies. These results support the notion that inhibitory and working memory tasks involve common neural components, which may provide a neural basis for the interrelationship between the two systems.

Age and redintegration in immediate memory and their relationship to task difficulty

It is commonly assumed that as short-term memory tasks become more difficult, a transient phonological trace that supports recall loses its fidelity. Recall can still be achieved through a process called redintegration, where long-term phonological or lexical knowledge is used to reconstruct the memory trace. In the present research, we explored age-related differences in the redintegration process by having older and younger participants study lists under different levels of task difficulty. As a means of examining the redintegration process, in Experiment 1, semantic similarity was manipulated, and in Experiment 2, phonological similarity was varied. The results show that similarity effects can be accurately predicted from knowledge of task difficulty with item scoring, but not with order scoring. The results support the redintegration perspective and indicate that although there may be differences in the absolute level of recall across age groups, the redintegration process is identical for younger and older participants.

Working memory, strategy execution, and strategy selection in mental arithmetic

A total of 72 participants estimated products of complex multiplications of two-digit operands (e.g., 63 x 78), using two strategies that differed in complexity. The simple strategy involved rounding both operands down to the closest decades (e.g., 60 x 70), whereas the complex strategy required rounding both operands up to the closest decades (e.g., 70 x 80). Participants accomplished this estimation task in two conditions: a no-load condition and a working-memory load condition in which executive components of working memory were taxed. The choice/no-choice method was used to obtain unbiased strategy execution and strategy selection data. Results showed that loading working-memory resources led participants to poorer strategy execution. Additionally, participants selected the simple strategy more often under working-memory load. We discuss the implications of the results to further our understanding of variations in strategy selection and execution, as well as our understanding of the impact of working-memory load on arithmetic performance and other cognitive domains.

The integration of familiarity and recollection information in short-term recognition: modeling speed-accuracy trade-off functions

Dual process models postulate familiarity and recollection as the basis of the recognition process. We investigated the time-course of integration of the two information sources to one recognition judgment in a working memory task. We tested 24 subjects with a response signal variant of the modified Sternberg recognition task (Oberauer, 2001) to isolate the time course of three different probe types indicating different combinations of familiarity and source information. We compared two mathematical models implementing different ways of integrating familiarity and recollection. Within each model, we tested three assumptions about the nature of the familiarity signal, with familiarity having (a) only positive values, indicating similarity of the probe with the memory list, (b) only negative values, indicating novelty, or (c) both positive and negative values. Both models provided good fits to the data. A model combining the outputs of both processes additively (Integration Model) gave an overall better fit to the data than a model based on a continuous familiarity signal and a probabilistic all-or-none recollection process (Dominance Model).

Developmental relations between working memory and inhibitory control

Working memory (WM) and inhibitory control (IC) are general-purpose resources that guide cognition and behavior. In this study, the developmental relations between WM and IC were investigated in 96 typically developing children aged 6 to 17 years in an experimental task paradigm using an efficiency metric that combined speed and accuracy performance. The ability to activate and process information in WM showed protracted age-related growth. Performance involving WM and IC together was empirically distinguishable from that involving WM alone. The results indicate that developmental improvements in WM are attributable to increased processing efficiency in activation, suppression, and strategic resource deployment, and that WM and IC are best studied in novel, complex situations that elicit competition among those resources.

Backward inhibition in a task of switching attention within verbal working memory

Three experiments were conducted to examine the backward inhibition effect in attention switching within verbal working memory. Experiment one showed significant backward inhibition effect in a "tri-count task". Experiment two suggested that the effect was not due to a perceptual inhibition on the previously presented figure. Experiment three excluded the sequential expectancy explanation for this inhibition effect. Our results suggest that attention switching between working memory items is accompanied by inhibition of the previously attended working memory item. The findings are discussed in respect to the account of the executive function.

Comparison of basic assumptions embedded in learning models for experience-based decision making

The present study examined basic assumptions embedded in learning models for predicting behavior in decisions based on experience. In such decisions, the probabilities and payoffs are initially unknown and are learned from repeated choice with payoff feedback. We examined combinations of two rules for updating past experience with new payoff feedback and of two choice rule assumptions for mapping experience onto choices. The combination of these assumptions produced four classes of models that were systematically compared. Two methods were employed to evaluate the success of learning models for approximating players' choices: One was based on estimating parameters from each person's data to maximize the prediction of choices one step ahead, conditioned by the observed past history of feedback. The second was based on making a priori predictions for the entire sequence of choices using parameters estimated from a separate experiment. The results indicated the advantage of a class of models incorporating decay of previous experience, whereas the ranking of choice rules depended on the evaluation method used.

Binding and inhibition in working memory: individual and age differences in short-term recognition

Two studies investigated the relationship between working memory capacity (WMC), adult age, and the resolution of conflict between familiarity and recollection in short-term recognition tasks. Experiment 1 showed a specific deficit of young adults with low WMC in rejecting intrusion probes (i.e., highly familiar probes) in a modified Sternberg task, which was similar to the deficit found in old adults in a parallel experiment (K. Oberauer, 2001). Experiment 2 generalized these results to 3 recognition paradigms (modified Sternberg, local recognition, and n back tasks). Old adults showed disproportional performance deficits on intrusion probes only in terms of reaction times, whereas young adults with low WMC showed them only in terms of errors. The generality of the effect across paradigms is more compatible with a deficit in content-context bindings subserving recollection than with a deficit in inhibition of irrelevant information in working memory. Structural equation models showed that WMC is related to the efficiency of recollection but not of familiarity.

Control of the contents of working memory--a comparison of two paradigms and two age groups

Two experiments investigated whether young and old adults can temporarily remove information from a capacity-limited central component of working memory (WM) into another component, the activated part of long-term memory (LTM). Experiment 1 used a modified Sternberg recognition task (S. Sternberg, 1969); Experiment 2 used an arithmetic memory-updating task. In both paradigms, participants memorized 2 lists, one of which was cued as temporarily irrelevant. Removal of the irrelevant list from capacity-limited WM was indexed by the disappearance of list-length effects of that list on latencies for concurrent processing tasks. Young adults could outsource the irrelevant list within 2-3 s and retrieve it back into the central part of WM later. Old adults showed the same flexibility in the arithmetic updating task but seemed somewhat less able or inclined to temporarily move information into the activated part of LTM in the modified Sternberg task.

Working memory and intelligence--their correlation and their relation: comment on Ackerman, Beier, and Boyle (2005)

On the basis of a meta-analysis of pairwise correlations between working memory tasks and cognitive ability measures, P. L. Ackerman, M. E. Beier, and M. O. Boyle (2005; see record 2004-22408-002) claimed that working memory capacity (WMC) shares less than 25% of its variance with general intelligence (g) and with reasoning ability. In this comment, the authors argue that this is an underestimation because of several methodological shortcomings and biases. A reanalysis of the data reported in Ackerman et al. using the correct statistical procedures demonstrates that g and WMC are very highly correlated. On a conceptual level, the authors point out that WMC should be regarded as an explanatory construct for intellectual abilities. Theories of working memory do not claim that WMC is isomorphic with intelligence factors but that it is a very strong predictor of reasoning ability and also predicts general fluid intelligence and g.

Mapping the Developmental Constraints on Working Memory Span Performance

This study investigated the constraints underlying developmental improvements in complex working memory span performance among 120 children of between 6 and 10 years of age. Independent measures of processing efficiency, storage capacity, rehearsal speed, and basic speed of processing were assessed to determine their contribution to age-related variance in complex span. Results showed that developmental improvements in complex span were driven by 2 age-related but separable factors: 1 associated with general speed of processing and 1 associated with storage ability. In addition, there was an age-related contribution shared between working memory, processing speed, and storage ability that was important for higher level cognition. These results pose a challenge for models of complex span performance that emphasize the importance of processing speed alone.

Effects of Subclinical Depression and Aging on Generative Reasoning About Linear Orders: Same or Different Processing Limitations?

The performance of older adults and depressed people on linear order reasoning is hypothesized to be best explained by different theoretical models. Whereas depressed younger adults are found to be impaired in generative inference making, older adults are well capable of making such inferences but exhibit problems with working memory (Experiments 1 and 2). Restriction of the available study time impairs reasoning by nondepressed control participants and. as such, proves to be a good model of older adults' but not depressed participants' limitations (Experiment 3). These results are replicated comparing depressed and older participants with a control group in the same study, providing increased power and linking the results to additional control measures of processing speed and working memory (Experiment 4).