Dual-task Processing Research Articles

Parallel dual-task processing and task-shielding in older and younger adults: Behavioral and diffusion model results

ABSTRACTBackground/Study Context: The study investigated the Backward Crosstalk Effect (BCE) in dual-task situations, that is, the observation that Task 2 characteristics can even influence Task 1 processing. This observation suggests that the tasks are processed in parallel. Besides determining the existence of a BCE in a group of older adults, the size of the BCE was compared to that in a group of younger adults. Importantly, recent studies yielded unclear results.Methods: Twenty-four younger and older adults (19–27 and 58–71 years of age, respectively) performed a dual-task experiment, where Task 1 required a left/right manual response and Task 2 required a left/right foot response. The BCE manifests in shorter Task 1 RTs if both responses are given on the same side (compatible) compared to when they are given on different sides (incompatible). Data were analyzed by Analyses of Variance and diffusion modeling.Results: Both age groups clearly exhibited a BCE, and the BCEs were of the same size. Further, for both age groups, the size of the BCE was similarly modulated by the previous trial’s compatibility status. Diffusion model analyses attribute the BCE to an increased drift rate in compatible compared to incompatible trials, and also revealed no age group differences in any of the analyzed parameters.Conclusion: The results point to an aspect of cognition that seems not to show age-related deteriorations, similar to, for example, n-2 repetition costs in task-switching situations. Certain response selection-related aspects of task processing are processed in parallel to the same degree in younger and older adults, and both age groups are similarly able to shield Task 1 processing from interfering Task 2 processing in a dual-task situation.

Neural correlates of dispositional pessimism and optimism on dual-task performance

Objective: Behavioral studies found that dispositional pessimism (DP) impairs cognitive task performance (i.e. dual task) such as in dual task processing as compared to dispositional optimism (DO). However, neuroanatomical corre-lates of these performance decrements are still unknown. Therefore, the current study aims at investigating neural correlates of pessimism and optimism on dual task performance. Methods: To test for this, two hundred participants were screened to create extreme groups of DP (i.e. 10 participants) and DO (11 participants) based on Life Orien-tation Test (LOT). The participants performed auditory and visual single tasks and dual tasks while their brain activity by means of functional magnetic resonance imaging (fMRI) was recorded. Results: Behavioral results showed that the groups have similar performance on single task performance whereas DP group slowed down on dual task performance as compared to DO group. Imaging results showed that DP group showed less dual task specific activations in inferior parietal and occipital cortices particularly in posterior cingulate gyrus, extending into precuneus and cuneus. Discussion: It has been concluded that DP impairs cognitive processing on dual task performance and this impairment accompanied by reduced activation in parietal and occipital cortices as compared to DO.

Categorization difficulty modulates the mediated route for response selection in task switching.

Conflict during response selection in task switching is indicated by the response congruency effect: worse performance for incongruent targets (requiring different responses across tasks) than for congruent targets (requiring the same response). The effect can be explained by dual-task processing in a mediated route for response selection, whereby targets are categorized with respect to both tasks. In the present study, the author tested predictions for the modulation of response congruency effects by categorization difficulty derived from a relative-speed-of-processing hypothesis. Categorization difficulty was manipulated for the relevant and irrelevant task dimensions in a novel spatial task-switching paradigm that involved judging the locations of target dots in a grid, without repetition of dot configurations. Response congruency effects were observed and they varied systematically with categorization difficulty (e.g., being larger when irrelevant categorization was easy than when it was hard). These results are consistent with the relative-speed-of-processing hypothesis and suggest that task-switching models that implement variations of the mediated route for response selection need to address the time course of categorization.

Hierarchical task organization in dual tasks: evidence for higher level task representations.

To examine whether hierarchical higher level task representations comprising the task sets of Task 1 (T1) and Task 2 (T2) are activated within each trial in dual-task situations, we combined the psychological refractory period (PRP) paradigm with the task-pair switching logic (Hirsch et al. 2017). In Experiment 1, in which subjects switched between task-pairs including a varying T1 and a constant T2, we found a PRP effect (i.e., worse performance with short stimulus onset asynchrony [SOA] than with long SOA) and task-pair switch costs in T1 and T2 (impaired performance in task-pair switches compared to task-pair repetitions). However, since in Experiment 1 there were no forward and backward response-response compatibility effects that indicated interference between T1 and T2, we could not exclude that the activation of T1 persisted into the next trial despite the intervening T2, and hence, that task-pair switch costs are due to repetition-priming effects of T1 across task-pairs rather than due to persisting activation of task-pair representations. In Experiment 2, we used a modified task-pair switching logic with a constant T1 and a varying T2, and replicated task-pair switch costs under conditions that not only rule out repetition-priming effects of T1 across task-pairs as the source of task-pair switch costs but also disentangle the effects of switching task-pairs from those of switching T1. These effects were associated in previous studies using the original task-pair switching logic. Thus, the findings of the present study strongly suggest that hierarchical higher level task representations are activated during dual-task processing.

P217 Disrupting cognitive control in dual-task situations by transcranial magnetic stimulation of the lateral prefrontal cortex

Introduction Performance in dual-task situations is usually impaired compared to performance in single-task situations, which is reflected in prolonged reaction times as well as increased error rates. These dual-task costs can be explained by the requirement to recruit additional task-order control processes that are crucial for scheduling, monitoring and regulating the processing order of two temporally overlapping tasks. Recent neuroimaging studies with functional magnetic resonance imagery (fMRI) could show that the lateral prefrontal cortex (lPFC) may play an essential role for implementing these control processes. However, the association between prefrontal activity and task-order control remains only correlational due to the nature of the fMRI method. Objectives The aim of this study was to provide evidence for the causal involvement of prefrontal activity in dual-task processing by applying transcranial magnetic stimulation (TMS). Methods 16 Participants performed a dual-task consisting of two simple choice reaction tasks. Demands on task-order control processes were manipulated by introducing dual-task blocks with either fixed or random order of both tasks. We compared the effects of TMS over the lPFC to two control conditions. Results As a result, we could show that in the stimulation condition dual-task performance decreased compared to control conditions only if demands on task-order control processes where high. Conclusion This pattern of results supports the conclusion that the lPFC plays a causal role for the implementation of task-order control processes in situations with temporally overlapping tasks. More specifically, we argue that the lPFC is recruited for activating an internal order representation into working memory.

Higher-order cognitive control in dual tasks: Evidence from task-pair switching.

In the present study, we combined the psychological refractory period (PRP) paradigm with a novel task-pair switching logic which enabled us to isolate performance costs occurring at the global level of task-pairs. In Experiment 1, in which we used conceptually overlapping responses for Task 1 (T1) and Task 2 (T2), we generated 3 task-pairs by combining 1 of 3 visual tasks (T1) with an auditory task (T2). In addition to worse performance after a short SOA than a long SOA (i.e., PRP effect), we found impaired performance in n - 1 task-pair switches as compared to n - 1 task-pair repetitions (i.e., n - 1 task-pair switch costs), suggesting that task-pairs were activated during dual-task processing. In Experiment 2, we increased the interference between T1 and T2 by using physically overlapping responses and we again observed n - 1 task-pair switch costs. To investigate whether the activation of task-pairs is adjusted by inhibitory control, we looked at the n - 2 task-pair sequence and found performance to be better in n - 2 task-pair repetitions than in n - 2 task-pair switches in both experiments. This n - 2 task-pair repetition benefit was replicated in Experiment 3 in which no immediate task-pair repetitions were included. Hence, the evidence suggests enhanced activation rather than inhibition as a crucial selection mechanism at the global level of dual-task processing. (PsycINFO Database Record

Home-based interventions improve trained, but not novel, dual-task balance performance in older adults: A randomized controlled trial

The purpose of this study was to compare the efficacy of four different home-based interventions on dual-task balance performance and to determine the generalizability of the four trainings to untrained tasks. Sixty older adults, aged 65 and older, were randomly assigned to one of four home-based interventions: single-task motor training, single-task cognitive training, dual-task motor-cognitive training, and dual-task cognitive–cognitive training. Participants received 60-min individualized training sessions, 3 times a week for 4 weeks. Prior to and following the training program, participants were asked to walk under two single-task conditions (i.e. narrow walking and obstacle crossing) and two dual-task conditions (i.e. a trained narrow walking while performing verbal fluency task and an untrained obstacle crossing while counting backward by 3s task). A nine-camera motion capture system was used to collect the trajectories of 32 reflective markers placed on bony landmarks of participants. Three-dimensional kinematics of the whole body center of mass and base of support were computed. Results from the extrapolated center of mass displacement indicated that motor-cognitive training was more effective than the single-task motor training to improve dual-task balance performance (p=0.04, ES=0.11). Interestingly, balance performance under both single-task and dual-task conditions can also be improved through a non-motor, single-task cognitive training program (p=0.01, ES=0.13, and p=0.01, ES=0.11, respectively). However, improved dual-task processing skills during training were not transferred to the novel dual task (p=0.15, ES=0.09). This is the first study demonstrating that home-based dual-task training can be effectively implemented to improve balance performance during gait in older adults.

Are participants' reports of their own reaction times reliable? Re-examining introspective limitations in active and passive dual-task paradigms

There is a known introspective limitation in the Psychological Refractory Period (PRP) paradigm — people underestimate the dual-task costs on their second reaction time. The prevailing explanation for this is that conscious awareness of the second stimulus is delayed in time until the first task has been centrally processed. Here, we examined this effect in more detail, by comparing reaction time estimates after processing a PRP task, and after passively experiencing ‘replays’ of PRP trials. Even when participants had no dual-task processing demands, they did not accurately report the reaction time intervals using a visual analogue scale (the original reporting method of most introspective PRP experiments), but they did when placing markers that represent each event on a timeline. Thus, the timeline seems to better represent participants' introspective representation of the trial. Importantly, introspection limitations still existed when participants processed the PRP task and then recreated it on a timeline.

Unchanging Capacity

Complex workspaces often require operators to divide attention between information within the visual periphery and a visual central task. For an air traffic controller, for example, monitoring complex displays while also watching for potential hazards is essential for avoiding aircraft collisions. In such environments, fast and accurate detection of peripheral events may be critical for safe performance. Presenting targets redundantly offers a potential way of speeding up target detection (Little, Eidels, Fific, & Wang, 2015; Townsend & Eidels, 2011). It remains unclear, however, whether redundant-target processing remains efficient with a concurrent central task. A series of experiments examined the effects of dual-tasking on peripheral redundant-target processing, either between- (Experiments 1a & 1b) or within-participants (Experiment 4). Furthermore, Experiments 2 and 3 manipulated target-distractor discriminability and distractor presence to examine the effects of target salience on dual-task processing efficiency. One hundred and one undergraduate students ( N =20 in each of Experiments 1a to 3; N = 21 in Experiment 4) performed a redundant-target task either by itself (Experiment 1a) or whilst performing a manual tracking task (Experiments 1b-4). The tracking task required participants to maneuver a joystick using both hands to align a cursor with a moving red target. The detection task required participants to press a joystick button bimanually whenever a target appeared at a location in the peripheral visual field. Experiments 1a, 1b, and Experiment 4 employed “T” as the target item and “L” as distractor items that appeared randomly rotated in 90° steps. In Experiment 2, target salience was increased by employing “X” as the target item and “O” for the distractor items. Experiment 3 tested peripheral target processing in the absence of distractors; hence, only the target item “T” was employed. Processing efficiency in the target-detection task was calculated using measures of resiliency (Little et al., 2015) or workload capacity (Townsend & Eidels, 2011). In all five experiments, processing of redundant targets was less efficient than predicted by a standard parallel race model (Raab, 1962; Townsend & Eidels, 2011). Surprisingly, processing efficiency differed negligibly between the single and dual-task conditions. Capacity may be protected from task-load effects due to separate information-processing resource pools within the central and peripheral visual fields (Wickens, 2002). Neither increasing the discriminability between targets and distractors, nor removing distractors entirely, had any effect on redundant-target processing efficiency. Results suggest target processing in the visual periphery is capacity-limited, but that processing efficiency is robust against changes to concurrent task load or target salience.

Increased Brain Activation for Dual Tasking with 70-Days Head-Down Bed Rest.

Head-down tilt bed rest (HDBR) has been used as a spaceflight analog to simulate the effects of microgravity exposure on human physiology, sensorimotor function, and cognition on Earth. Previous studies have reported that concurrent performance of motor and cognitive tasks can be impaired during space missions. Understanding the consequences of HDBR for neural control of dual tasking may possibly provide insight into neural efficiency during spaceflight. In the current study, we evaluated how dual task performance and the underlying brain activation changed as a function of HDBR. Eighteen healthy men participated in this study. They remained continuously in the 6° head-down tilt position for 70 days. Functional MRI for bimanual finger tapping was acquired during both single task and dual task conditions, and repeated at 7 time points pre-, during- and post-HDBR. Another 12 healthy males participated as controls who did not undergo HDBR. A widely distributed network involving the frontal, parietal, cingulate, temporal, and occipital cortices exhibited increased activation for dual tasking and increased activation differences between dual and single task conditions during HDBR relative to pre- or post-HDBR. This HDBR-related brain activation increase for dual tasking implies that more neurocognitive control is needed for dual task execution during HDBR compared to pre- and post-HDBR. We observed a positive correlation between pre-to-post HDBR changes in dual-task cost of reaction time and pre-to-post HDBR change in dual-task cost of brain activation in several cerebral and cerebellar regions. These findings could be predictive of changes in dual task processing during spaceflight.

EP 124. Dual-task processing in young and older adults

Introduction A substantial body of research has indicated impairments in dual-task performance with advanced age. Aim To corroborate previously reported age effects on dual-task performance and to examine potential moderating factors. In particular, we examined associations between dual-tasking and visuomotor coordination, cognitive flexibility, divided attention and task-switching. Methods The sample consisted of 20 young (mean age: 25.7 yrs.) and 20 elderly (mean age: 57.4 yrs.) adults. Dual-task performance was assessed using the well-established psychological refractory period (PRP) paradigm, in which two speeded choice-reaction tasks need to be performed either simultaneously or successively. Task 1 required a discrimination of high and low tones; Task 2 required a discrimination of letters “a” and “e”. A variable stimulus onset asynchrony (SOA; 50, 100, 350 or 800 ms) separated the two tasks. In addition, several tests were conducted to assess potential influencing factors including the Trail-Making Test (TMT) for visuomotor coordination and cognitive flexibility, a cross-modal divided-attention test, and an alternating-runs task-switching paradigm producing global and local switch costs. Results We observed typical dual-task costs for response speed (i.e., a significant PRP effect on reaction time, RT) but neither found a significant main effect of age on RT, nor a significant interaction between age and dual-task costs for RT in either Task. In the letter discrimination, however, there was a significant interaction between age and dual-task costs for accuracy driven by a more steeply increasing error rate with increasing task overlap in the older (vs. young) group. Neither visuomotor coordination nor cognitive flexibility co-varied with dual-task costs in RT and accuracy, but divided-attention and task-switching performance did. Difficulties in dividing attention and larger local switch costs were associated with a larger PRP effect on RT but not on accuracy. Conclusion When two speeded reaction tasks need to be performed in parallel, healthy aging may lead to deterioration in accuracy, rather than speed, relative to serial task processing. With regard to speed, however, both the ability to efficiently divide attention across sensory modalities and the ability to shift to a given task right after performing another one significantly predict low dual-tasking costs. As to accuracy, the pattern appears to be reversed, with age, rather than divided-attention or task-switching abilities, compounding dual-tasking costs. This suggests that doing two things at once is not per se compromised in old age but may depend more strongly on the integrity of other executive functions such as attentional control and task-set activation. Also, differential speed-accuracy tradeoffs need to be considered when studying age effects on performance.

Dual-task (postural and cognitive) processing in healthy persons and traumatic brain injury patients

Dual-task (postural and cognitive) processing in healthy persons and traumatic brain injury patients

Never Too Much? The Curvilinear Relationship Between Empowering Leadership and Task Performance

Although empowering leadership is generally considered to be a desirable leadership approach, its effectiveness has been questioned and the response is mixed. Integrating the “Too-Much-of-a-Good-Thing” effect and dual task processing, this study examines the relationship between empowering leadership and task performance. Specifically, we suggest a curvilinear relationship between empowering leadership and employee task performance. Further, applying a leadership contingency perspective, we propose that the curvilinear relationship between empowering leadership and employee task performance is moderated by employee learning orientation. Using survey data from 137 supervisor–subordinate dyads, our results show that the inverted U-shaped relationship between empowering leadership and employee task performance is moderated by employee learning orientation. Theoretical and practical implications are discussed.

Neural Mechanisms Underlying the Performance Limitations in Dual-Task Situations

Simultaneous performance of two tasks often results in degradation of performance in either or both tasks. This effect is known as dual-task interference and thought to be caused by the capacity limitation of cognitive resources used for cognitive processes. There have been several questions regarding dual-tasking in cognitive neuroscience: which brain area specifically participates in dual-task processing, what are cognitive resources, where are the cognitive resources located in the brain, what neural mechanism limits the capacity of cognitive resources, and whether cognitive resources are modality-specific or modality-general. Although human neuroimaging studies revealed that the prefrontal cortex plays an essential role in the dual-task performance, these studies could not determine the brain area specific for dual-task processing; however, the results of these studies supported the overlap hypothesis, which explains the neural mechanisms for allocating cognitive resources and the interference effect between two tasks during dual-task performances. Recent neurophysiological studies using monkeys revealed that neurons exhibiting dual-task selective activity are present in the prefrontal cortex and that dual-task interference is caused by the simultaneous and overloaded recruitment of the same prefrontal neural population by the two tasks. These results provide direct neural evidence for psychological concepts of cognitive resources and its capacity limitation.

Brain activation during dual-task processing is associated with cardiorespiratory fitness and performance in older adults.

Higher cardiorespiratory fitness is associated with better cognitive performance and enhanced brain activation. Yet, the extent to which cardiorespiratory fitness-related brain activation is associated with better cognitive performance is not well understood. In this cross-sectional study, we examined whether the association between cardiorespiratory fitness and executive function was mediated by greater prefrontal cortex activation in healthy older adults. Brain activation was measured during dual-task performance with functional magnetic resonance imaging in a sample of 128 healthy older adults (59–80 years). Higher cardiorespiratory fitness was associated with greater activation during dual-task processing in several brain areas including the anterior cingulate and supplementary motor cortex (ACC/SMA), thalamus and basal ganglia, right motor/somatosensory cortex and middle frontal gyrus, and left somatosensory cortex, controlling for age, sex, education, and gray matter volume. Of these regions, greater ACC/SMA activation mediated the association between cardiorespiratory fitness and dual-task performance. We provide novel evidence that cardiorespiratory fitness may support cognitive performance by facilitating brain activation in a core region critical for executive function.

Isolating a mediated route for response congruency effects in task switching.

Response congruency effects in task switching reflect worse performance for incongruent targets associated with different responses across tasks than for congruent targets associated with the same response. In the present study, the author investigated whether the effects can be produced solely by a mediated route for response selection, whereby targets are categorized with respect to both tasks, as opposed to a nonmediated route, whereby target-response instances from past experience are retrieved directly from long-term memory. The mediated route was isolated in 3 experiments by having subjects perform semantic categorization tasks on targets that were never repeated, thereby making the nonmediated route nonfunctional. Robust response congruency effects were observed for both response time and error rate in all experiments, indicating that the mediated route is sufficient to produce such effects by itself. The results imply that subjects engaged in dual-task processing despite no requirement to do so, raising questions about the modeling of response selection in task-switching situations.

二重課題の神経生物学：二重課題干渉効果と前頭連合野の役割

二重課題の神経生物学：二重課題干渉効果と前頭連合野の役割

ERP correlates of prospective memory and cognitive control during dual-task and abrupt task switch processing.

ERP correlates of prospective memory and cognitive control during dual-task and abrupt task switch processing.

Does Initial Performance Variability Predict Dual-Task Optimization with Practice in Younger and Older Adults?

Background/Study Context: The variability associated with reaction time (RT) is sometimes considered as a proxy for inefficient neural processing, particularly in old age and complex situations relying upon executive control functions. Here, it is examined whether the amount of variability exhibited early in practice can predict the amount of improvement with later practice in dual-task performance, and whether the predictive power of variability varies between younger and older adults.Methods: To investigate the relationship between variability and practice-related improvement, RT mean and variability data are used, obtained from an experiment in which younger and older adults performed two tasks in single-task and dual-task conditions across seven practice sessions. These RT and variability data were related to the single-task and dual-task practice benefits. These benefits were computed as follows: dual-task/single-task RTs at the beginning of practice minus dual-task/single-task RTs at the end of practice.Results: In both age groups, dual-task processing was speeded up with practice and variability associated with the means was reduced. Most important, independent of mean RTs, variability allowed predicting dual-task practice benefit in both age groups under specific conditions.Conclusion: These findings suggest that the relationship between performance variability and executive control functions under some specific conditions. Implications of these results for models of practiced dual tasks are discussed.

Pickin’, singin’, and attendin’: Possible limitations on human processing at the highest level of accomplishment.

Psychologists have long investigated whether humans can carry out more than one task at once. In music, the classic example of a dual-task performance is singing while playing an instrument. That is, if a vocalist accompanies him- or herself on guitar, successful performance requires the simultaneous maintenance of pitch and rhythmic accuracy on two separate instruments. Laboratory studies investigating dual-task performance, though usually involving the tracking of visual stimuli, have found typically that performance on either task can suffer (for review see Pashler, 1998). More recent studies of musicians have shown that there are instances in which complicated tonal and rhythmic processing can be coordinated quite well (Keller & Repp, 2008), but that the coordination of two musical tasks is difficult and relevant to the cognition of human dual-task performance.To account for the difficulty in combining two tasks, theorists have postulated processing limitations of various sorts in human cognition. One such limitation is a bottleneck: a structural limit in the cognitive system. Another processing-limitation view postulates a finite pool of resources available for carrying out cognitive activities. If tasks demand more of those resources than are available, performance on one or more task will suffer. Recent studies have provided support for several different sorts of predictions emanating from the bottleneck and resources views (see Kamienkowski, Pashler, Dahaene, & Sigman, 2011; Levy & Pashler, 2001).The study of dual-task processing has not been without controversy, however. Although the processing-limitation perspective has been dominant, there has been interest in the possibility that humans can carry out multiple tasks concurrently, and without error. Allport, Antonis, and Reynolds (1972) found that music students could accurately sight-read music while shadowing verbal material (see also Shaffer, 1975). The Executive Processing Interaction and Control model of Meyer and Kieras (1997a, b), postulates no structural limitations to human processing (but see Anderson, 2007). Deficits in dual-processing can occur in three ways: (a) interference due to stimulus or response overlap, which can be eliminated by using tasks from different domains; (b) lack of practice in combining tasks, which can be eliminated by practicing tasks conjointly; and (c) participants' strategies, arising from instructions giving one task priority, which can be eliminated by placing emphasis on both tasks. Studies have demonstrated equivalent levels of performance by individuals carrying out two tasks concurrently versus separately (Hazeltine, Teague, & Ivry, 2002; Oberauer & Kliegl, 2004; Schumacher et al., 2001; but see Levy & Pashler, 2001). Hirst, Spelke, Reaves, Caharack, and Neisser (1980) showed that dual-task performance can be increased by practice in carrying out tasks conjointly, although their participants were not able to reach the point of being able to carry out two demanding tasks without error (see also Oberauer & Kliegl, 2004).Understanding multiple-task performance promises to illuminate basic aspects of human information processing, and the findings may facilitate our understanding of situations in which humans try to carry out multiple tasks, beyond musical examples. However, questions can be raised concerning recent studies that have found errorless dual-task performance. First, a number of more recent studies have produced results that can be interpreted as supporting the idea that there are limitations to human processing capacity that may be extremely difficult if not impossible to overcome (Kamienkowski, Pashler, Dahaene, & Sigman, 2011; Levy, Pashler, & Boer, 2006; Pashler, Johnston, & Ruthruff, 2001; Ruthruff, Johnston, & Van Selst, 2001; Van Selst, Ruthrauff, & Johnston, 1999). A second problem with demonstrations of errorless dual-task performance comes from the fact that that conclusion depends on acceptance of the null hypothesis-no differences are found between dual-task versus single-task conditions-which requires that we have confidence in the sensitivity of our design to detect processing limitations. …