Constraints on using the dual-task methodology to specify the degree of central executive involvement in cognitive tasks

The dual-task paradigm has been used to examine the role of the central executive in various cognitive tasks. In these studies, performance decrements in primary cognitive tasks performed concurrently with secondary executive tasks have been interpreted as evidence for the involvement of the central executive in those primary tasks. In the present study, we examined the effects of different secondary tasks on performance of three psychometric visuospatial tasks. The decrement in performance of these tasks when they were paired with secondary executive tasks was smallest for the psychometric task considered to most heavily involve the central executive and largest for the task considered least demanding of executive mechanisms. We propose that, when applied to the assessment of central executive involvement, the prevalent simple dual-task logic does not always apply. Special conditions that limit the application of the dual-task methodology include two inherently related factors--a response selection bottleneck and a strategic tradeoff between primary and secondary tasks.     

Do attentional capacities and processing speed mediate the effect of age on executive functioning?

The executive processes are well known to decline with age, and similar data also exists for attentional capacities and processing speed. Therefore, we investigated whether these two last nonexecutive variables would mediate the effect of age on executive functions (inhibition, shifting, updating, and dual-task coordination). We administered a large battery of executive, attentional and processing speed tasks to 104 young and 71 older people, and we performed mediation analyses with variables showing a significant age effect. All executive and processing speed measures showed age-related effects while only the visual scanning task performance (selective attention) was explained by age when controlled for gender and educational level. Regarding mediation analyses, visual scanning partially mediated the age effect on updating while processing speed partially mediated the age effect on shifting, updating and dual-task coordination. In a more exploratory way, inhibition was also found to partially mediate the effect of age on the three other executive functions. Attention did not greatly influence executive functioning in aging while, in agreement with the literature, processing speed seems to be a major mediator of the age effect on these processes. Interestingly, the global pattern of results seems also to indicate an influence of inhibition but further studies are needed to confirm the role of that variable as a mediator and its relative importance by comparison with processing speed.     

Les modifications du fonctionnement exécutif dans le vieillissement normal

We provide here an overview of the current state of research in the domain of executive functioning in normal aging. Normal aging has generally been associated with executive control deficits. Although impaired performance is effectively observed for the executive functions of updating, shifting, inhibition and dual-task coordination, preserved performance is also sometimes observed. We interpreted the presence of preserved performance as reflecting the integrity of some executive sub-processes or the existence of distinct functions within an executive function previously considered as unitary. Moreover, these difficulties appear also influenced by the efficiency of attentional processes (i.e., processing speed), working memory capacity and some individual genetic characteristics. Changes in the neural networks associated to executive processes were also reported. These changes consist in increased or decreased activity in task-related networks, or the recruitment of supplementary brain areas. They are considered to reflect compensatory processes or inefficient use of brain networks, when they are respectively associated to preserved or impaired task-performance.     

The role of control functions in mentalizing: dual-task studies of theory of mind and executive function

Conflicting evidence has arisen from correlational studies regarding the role of executive control functions in Theory of Mind. The current study used dual-task manipulations of executive functions (inhibition, updating and switching) to investigate the role of these control functions in mental state and non-mental state tasks. The 'Eyes' pictorial test of Theory of Mind showed specific dual-task costs when concurrently performed with an inhibitory secondary task. In contrast, interference effects on a verbal 'Stories' task were general, occurring on both mental state and non-mental state tasks, and across all types of executive function. These findings from healthy functioning adults should help to guide decisions about appropriate methods of assessing ToM in clinical populations, and interpreting deficits in performance in such tasks in the context of more general cognitive dysfunction.     

The role of semantic memory in short-term recall: effect of strategic retrieval ability in an elderly population

The present paper examines the relationship between two classic phenomena: semantic effects in short-term recall (STR) tasks, which are interpreted as indicating the involvement of long-term memory (LTM) in the functioning of short-term memory, on the one hand, and the existence of individual differences amongst elderly people in strategic retrieval ability (i.e., the ability to activate representations in LTM in a controlled way) on the other hand. Forty elderly participants completed a STR task under four different conditions which were thought to differentially involve LTM representations. Several executive functions, among which the strategic retrieval ability, were evaluated. The results showed that the participants who obtained the best performances in terms of strategic retrieval ability, and only in this executive ability, also exhibited better performances in the STR task, in particular when this task was performed under conditions which favored the use of LTM.     

Practice-related optimization and transfer of executive functions: a general review and a specific realization of their mechanisms in dual tasks

Improvements in performing demanding and complex task situations are typically related to the optimization of executive functions and efficient behavioral control. The present study systematizes and reviews the optimization of different executive function types: Shifting, Inhibition, Updating, and Dual tasking. In particular, we focus on optimisations of these functions with training and on transfer effects of related training skills to non-trained situations. The aim of the study’s empirical part (see also Appendix) was to investigate the specific mechanisms of executive functions in the context of Dual tasking, leading to improved dual-task performance after practice. More specifically, we tested the Efficient Task Instantiation (ETI) model that includes specific assumptions regarding practice-related improvements of executive task coordination skills: Dual-task performance is improved with practice because of an efficient and conjoint instantiation of sets of relevant task information in working memory at the onset of a dual task. According to our knowledge, the ETI model is one of the first that allows illustrating the contribution of cognitive mechanisms underlying practice-related improvements in performing dual tasks and the impact of task coordination skills on this performance.     

Strategic encoding and retrieval processes in verbal recall among middle-aged and older adults

The authors used an analysis of individual differences to examine the role of executive control in strategic encoding and retrieval in verbal recall. Participants enrolled in the Louisiana Healthy Aging Study completed measures of working memory (WM), cognitive status, vocabulary, and free recall of words. Indices of clustering in free recall were calculated to permit inferences on strategic encoding and retrieval processes. We hypothesized that WM would be more strongly associated with strategic encoding and retrieval metrics than vocabulary based on the assumption that successful remembering requires executive control in WM. Regression analyses, together with a variance portioning procedure, confirmed that WM had comparable levels of unique and shared variance with the strategic encoding and retrieval metrics, and both exceeded vocabulary. Theoretical and clinical implications of these data are considered, with the suggestion of future research in lifespan samples as opposed to exclusively young adult or older adult samples.     

Rehabilitation of executive deficits in closed head injury and anterior communicating artery aneurysm patients

This paper reports a study that was aimed to rehabilitate executive functions in closed head injury (CHI) and anterior communicating artery (ACoA) aneurysm patients. The groups tested comprised 10 CHI patients, 9 ACoA aneurysm patients and 19 controls. We employed a dual-task paradigm that is known to tap the ability to co-ordinate two actions. The treatment consisted of five experimental sessions, in which the dual-task paradigm was used. In the CHI study, the dual-task cost was measured before the treatment (assessment), immediately after the treatment (retest), and 3 months after the treatment (follow-up). In the ACoA aneurysm study, the dual-task cost was also assessed 12 months after the treatment. A significant reduction of the dual-task cost from assessment to retest was found. This reduction remained stable in the follow-up sessions. The results are discussed with reference to the absence of spontaneous recovery of this specific executive function and to the possibility that the beneficial effect of the treatment generalises to other executive functions and/or daily living activities. Received: 31 March 1999 / Accepted: 23 July 1999     

Aging and strategic retrieval in a cued-recall test: the role of executive functions and fluid intelligence

Cued-recall in episodic memory was investigated in relation to low and high cognitive support at retrieval, executive function level and fluid intelligence level in 81 healthy adults divided first into two age groups (young and elderly adults). The first analyses showed that age-related differences were greater when a low cognitive support was provided to recall the words. An individual index of loss of performance when the number of cues was decreased was then calculated. Hierarchical regression analysis revealed that the executive functions measure (perseverative errors on the Wisconsin Card Sorting Test) was a better candidate than the fluid intelligence measure (Cattell's culture fair test) to account for the age-related variance of the size of performance loss. These findings suggest that age differences in implementing strategic retrieval may be mainly due to a decline in executive functions.     

Differential contributions of set-shifting and monitoring to dual-task interference

It is commonly argued that complex behaviour is regulated by a number of "executive functions", which work to coordinate the operation of disparate cognitive systems in the service of an overall goal. However, the identity, roles, and interactions of specific putative executive functions remain contentious, even within widely accepted tests of executive function. The authors present two experiments that use dual-task interference to provide further support for multiple distinct executive functions and to establish the differential contributions of those functions in two relatively complex executive tasks-random generation and the Wisconsin Card Sorting Test. Results are interpreted in terms of process models of the complex executive tasks.     

Differential contributions of set-shifting and monitoring to dual-task interference

It is commonly argued that complex behaviour is regulated by a number of “executive functions”, which work to coordinate the operation of disparate cognitive systems in the service of an overall goal. However, the identity, roles, and interactions of specific putative executive functions remain contentious, even within widely accepted tests of executive function. The authors present two experiments that use dual-task interference to provide further support for multiple distinct executive functions and to establish the differential contributions of those functions in two relatively complex executive tasks—random generation and the Wisconsin Card Sorting Test. Results are interpreted in terms of process models of the complex executive tasks.     

Visual search does not remain efficient when executive working memory is working

Working memory (WM) has been thought to include not only short-term memory stores but also executive processes that operate on the contents of memory. The present study examined the involvement of WM in search using a dual-task paradigm in which participants performed visual search while manipulating or simply maintaining information held in WM. Experiments 1a and 2a involved executive WM tasks that required counting backward from a target digit and sorting a string of letters alphabetically, respectively. In both experiments, the search slopes in the dual-task condition were significantly steeper than those in a search-alone condition, indicating that performing the WM manipulation tasks influenced the efficiency of visual search. In contrast, when information was simply maintained in WM (Experiments 1b and 2b), search slopes did not differ between the single- and dual-task conditions. These results suggest that WM resources related to executive functions may be required in visual search.     

Phonological storage and executive function deficits in children with mathematics difficulties

Children with mathematics difficulties suffer from working memory deficits. This study investigated the deficit profile of phonological storage and executive functions in working memory among children with mathematics difficulties. Based on multiple instruments and two assessment points, 68 children were screened out of 805 fifth graders. Of these 68 children, 18 were classified as children with only mathematics difficulties (MD), 20 were classified as children with mathematics and reading difficulties (MDRD), and 30 were typically developing (TD) peers matched on age and general ability. Measures for phonological storage, dual-task performance, inhibition, and updating of verbal and numerical materials were administered individually. Results showed that compared with the TD group, children with MD exhibited storage and inhibition deficits specific to numerical information and dual-task deficits of both verbal and numerical information, whereas children with MDRD showed extensive deficits on phonological storage and executive functions on both verbal and numerical tasks. Moreover, executive function deficits were not confined to phonological storage deficits. Implications of the findings for the working memory deficit profile and working memory training among children with mathematics difficulties were discussed.     

The roles of the central executive and visuospatial storage in mental arithmetic: A comparison across strategies

Previous research has demonstrated that working memory plays an important role in arithmetic. Different arithmetical strategies rely on working memory to different extents—for example, verbal working memory has been found to be more important for procedural strategies, such as counting and decomposition, than for retrieval strategies. Surprisingly, given the close connection between spatial and mathematical skills, the role of visuospatial working memory has received less attention and is poorly understood. This study used a dual-task methodology to investigate the impact of a dynamic spatial n-back task (Experiment 1) and tasks loading the visuospatial sketchpad and central executive (Experiment 2) on adults' use of counting, decomposition, and direct retrieval strategies for addition. While Experiment 1 suggested that visuospatial working memory plays an important role in arithmetic, especially when counting, the results of Experiment 2 suggested this was primarily due to the domain-general executive demands of the n-back task. Taken together, these results suggest that maintaining visuospatial information in mind is required when adults solve addition arithmetic problems by any strategy but the role of domain-general executive resources is much greater than that of the visuospatial sketchpad.     

Dual-task influences on retrieval from semantic memory and coordination dynamics

Bimanual 1:1 rhythmic coordination was performed while retrieving words from a specified category. The effects of divided attention (DA) on coordination were indexed by changes in mean relative phase and recurrence measures of shared activity between the two limbs. Effects of DA on memory were indexed by deficits in exemplars retrieved relative to the baseline. Shifts in relative phase were found, accompanied by a recall deficit for DA during the retrieval task. DA also reduced the degree of shared activity between left and right rhythmic motions. Our discussion focuses on DA-induced parameter changes in retrieval and coordination dynamics, as well as on the hypothesis that stability is the general factor mediating dual-task performance.     

Timing and executive function: Bidirectional interference between concurrent temporal production and randomization tasks

A review of interference effects in concurrent temporal/nontemporal dual-task studies suggests that prospective timing may be related to executive cognitive functions. Executive processes play a supervisory role in behavior by controlling attention, coordinating information, and scheduling actions. In the present research, a timing task was paired with an established executive task in a dual-task paradigm. The timing task required subjects t o generate a series o f 5-sec temporal productions,and the executive task was random number generation. These tasks were performed both separately and concurrently. Comparisons of single-task and dual-task conditions showed that (1) the randomization task interfered with timing by making temporal productions more variable and longer and (2) concurrent timing disrupted randomization performance by making responses less random. This pattern of bidirectional interference supports the idea that timing relies on the same attentional resources used by other executive-level tasks.     

Disentangling executive functions and memory processes in event‐based prospective remembering after brain damage: A neuropsychological study

Successful prospective remembering (PR) comprises at least two components: one retrospective component that refers to the encoding and retrieval of the content of the intention and a second prospective component that involves the retrieval of the intended action at the appropriate moment. Whereas the retrospective component is very similar to memory skills like learning and retention of new information, the prospective component is thought to rely mainly on executive function. Head injuries can disturb PR during both of these stages. To disentangle the relative impact of executive functions and retrospective memory processes on PR we embedded a PR task in a 2‐back verbal working memory paradigm. Fifty‐six neurological patients with brain damage of various aetiologies were divided pre‐experimentally into four groups on the basis of their delayed recall Index in the Wechsler Memory Scale‐Revised (WMS‐R, indicating absence or presence of deficits in retrospective memory functions) and their age‐corrected score in the Behavioural Assessment of the Dysexecutive Syndrome (BADS, indicating absence or presence of deficits in executive functions). Additionally, 19 controls matched for age and education were examined. We found that patients with deficits in executive functions detected fewer cues than any other group irrespective of their retrospective memory performance. However, eight patients with severe anterograde memory deficits could retain neither the intention nor its content. Thus, intactness of the retrospective component seems to be a necessary but not sufficient prerequisite for successful prospective remembering. For the execution of the intended action itself executive functions play a critical role.     

Retrieval-Induced Forgetting and Executive Control

ABSTRACT— Retrieving information from long-term memory can lead people to forget previously irrelevant related information. Some researchers have proposed that this retrieval-induced forgetting (RIF) effect is mediated by inhibitory executive-control mechanisms recruited to overcome interference. We assessed whether inhibition in RIF depends on executive processes. The RIF effect observed in a standard retrieval-practice condition was compared to that observed in two different conditions in which participants had to perform two concurrent updating tasks that demanded executive attention. Whereas the usual RIF effect was observed when retrieval practice was performed singly, no evidence of forgetting was found in the dual-task conditions. Results strongly suggest that inhibition involved in RIF is the result of executive-control processes.     

Field dependence-independence from a working memory perspective: a dual-task investigation of the Hidden Figures test

Field dependence-independence (FDI) is a construct intensively investigated within cognitive style research, but its cognitive underpinnings are not clearly specified. We propose that performance on FDI tasks primarily reflects the operations of the visuospatial and executive components of working memory. We tested this hypothesis in a dual-task experiment with a commonly used measure of FDI, the Hidden Figures Test. The results showed that performance on this test was impaired by concurrent performance of secondary tasks that primarily tap the visuospatial component (spatial tapping) and the executive component (2-back and random number generation), but was almost unaffected by other secondary tasks (simple tapping and articulatory suppression). Moreover, an analysis of secondary task performance ruled out the possibility of strategic trade-offs and revealed an intriguing dissociation for two different sets of "randomness" indices for the random number generation task. These results support the hypothesised mapping between FDI and working memory components and suggest that the dual-task paradigm can provide a useful way to bring underspecified constructs like FDI into closer alignment with theoretical ideas developed within cognitive psychology.     

Recognition,recollection, familiarity and executive function in medicated patients with moderate Parkinson's disease

There is conflicting evidence about whether Parkinson's disease (PD) is associated with deficiencies in recognition memory (RM) and the processes which underlie it, namely recollection (a form of recall) and familiarity (a feeling of memory in the absence of recall). The aims of the current study were to examine forced‐choice verbal RM (assessed with the Warrington Recognition memory Test), yes‐no RM, recollection, familiarity and executive functioning in 17 patients with moderate PD and 17 healthy volunteers matched for age and premorbid intelligence. We predicted that patients with moderate PD would display a significant recollection deficit on the yes‐no RM test, because their strategic memory processing that depends on executive functioning and is necessary for efficient encoding and/or retrieval, was disrupted. In contrast, familiarity memory, which is not dependent on these processes, and forced‐choice RM (which is largely dependent on familiarity) should show higher levels of preservation. We also predicted that recollection should be correlated with severity of executive dysfunction. Our findings revealed that the PD patients were as likely to accurately discriminate between targets and distractors as the healthy volunteers on both RM tests. However, the PD patients were significantly less reliant on recollection‐driven recognition decisions on the yes‐no RM test when compared with the healthy control group. The patients also displayed executive function deficits, but these were not correlated with recollection. The extent to which the PD patients' reliance on familiarity at the expense of recollection is explained by impairments in strategic memory processes/executive function and/or medial temporal lobe retrieval processes needs further exploration.