Performance Of Multiple Tasks Research Articles

Balance, Attention, and Dual-Task Performance During Walking After Brain Injury

To examine the relationship between balance, attention, and dual-task performance in individuals with acquired brain injury. Cross-sectional study. Rehabilitation center and supported living program. Twenty-four individuals aged 18 to 58 years (mean = 39 years) with acquired brain injury who were able to ambulate 40 ft with (29%) or without an assistive device. Fifty-eight percent were independent community ambulators. Fifty-four percent had fallen in the past 6 months; and 42% reported feeling unsteady with standing or walking. Participants completed a battery of balance, attention, and dual-task assessments. Balance: Berg Balance Scale (BBS), Four Square Step Test (FSST), High Level Mobility Assessment Test (HiMAT); Attention: Symbol Digit Modalities Test (SDMT), Moss Attention Rating Scale (MARS), modified for a single test session; and a walking dual-task assessment, the Walking and Remembering Test. Mean scores: BBS, 48 of 56; FSST, 19.6 seconds; HiMAT, 20 of 54; SDMT, 30 correct; and MARS, 80. Dual-task costs were observed with variable patterns across subjects: 48% demonstrated primarily motor slowing, 9% had reduced cognitive accuracy without motor slowing, and 35% demonstrated decrements in both tasks. Subjects with a falls history had more impaired balance (HiMAT, BBS, and FSST, all P <.026) but were not significantly different in dual-task performance or attention measures. The test battery matched the range of motor and cognitive abilities of the sample. Balance was more strongly related to falls history than measures of attention or dual-task performance. Injury chronicity may have allowed some subjects to develop strategies to optimize dual-task performance. Alternatively, motor slowing in dual-task conditions may be an adaptive strategy, allowing performance of multiple tasks with reduced safety risk. Further investigation in this area is warranted to clarify the utility of dual-task methods in identifying falls risk after brain injury.

Forearm posture and grip effects during push and pull tasks

Direction of loading and performance of multiple tasks have been shown to elevate muscle activity in the upper extremity. The purpose of this study was to evaluate the effects of gripping on muscle activity and applied force during pushing and pulling tasks with three forearm postures. Twelve volunteers performed five hand-based tasks in supinated, neutral and pronated forearm postures with the elbow at 90° and upper arm vertical. All tasks were performed with the right (dominant) hand and included hand grip alone, push and pull with and without hand grip. Surface EMG from eight upper extremity muscles, hand grip force, tri-axial push and pull forces and wrist angles were recorded during the 10 s trials. The addition of a pull force to hand grip elevated activity in all forearm muscles (all p < 0.017). During all push with grip tasks, forearm extensor muscle activity tended to increase when compared with grip only while flexor activity tended to decrease. Forearm extensor muscle activity was higher with the forearm pronated compared with neutral and supinated postures during most isolated grip tasks and push or pull with grip tasks (all p < 0.017). When the grip dynamometer was rotated so that the push and pull forces could act to assist in creating grip force, forearm muscle activity generally decreased. These results provide strategies for reducing forearm muscle loading in the workplace. Statement of Relevance: Tools and tasks designed to take advantage of coupling grip with push or pull actions may be beneficial in reducing stress and injury in the muscles of the forearm. These factors should be considered in assessing the workplace in terms of acute and cumulative loading.

Development and evaluation of an ergonomic software package for predicting multiple-task human performance and mental workload in human–machine interface design and evaluation

Predicting human performance and mental workload in multiple task situations at an early stage of system design can save a significant amount of time and cost. However, existing modeling tools either can only predict human performance or require users of tools to learn a new programming language. Queueing Network-Model Human Processor (QN-MHP) is a new cognitive architecture for modeling both human performance and mental workload in multiple tasks. This paper describes the development of a Visual Basic Application in Excel (VBA) software package and an illustrative case study to evaluate its effectiveness. The software package has an easy-to-use user interface for QN-MHP that assists users of the modeling tool to simulate a dual task including definition of the tasks and interfaces by clicking buttons to select options and filling texts in a table, with no need to learn a simulation language. It allows the model user to intuitively observe the information processing state of the model during simulation, and conveniently compare the simulated human performance and mental workload for different designs. The illustrative case study showed that naïve users without prior simulation language programming experience can model human performance and mental workload in a complex multitask situation within 3 min; and this software package can save 71% of modeling time and reduce 30% of modeling errors. Further developments of the VBA software package of QN-MHP are also discussed on how to make it a comprehensive proactive ergonomic design and analysis tool.

Accommodating ‘Mrs. Three‐in‐One’: homemaking, home entertaining and domestic advice literature in post‐war Britain

This article analyses the effects of the ‘servant problem’, meaning the contraction of the domestic service industry in the twentieth century, as represented in domestic advice literature (etiquette, homemaking and home decoration books). Before World War II, domestic advisors assumed that readers employed staff, while by the 1970s no such assumption could be made. Managing a home unassisted, especially when entertaining guests in the role American etiquette expert Emily Post termed ‘Mrs. Three‐in‐One’ (hostess, cook and waitress at once), formed an enduring topic for British and North American domestic advice writers between 1920 and 1970. Rather than reapportioning parts of the homemaker’s labour to other family members, the solutions offered by domestic advisors revolved around reshaping domestic space and its uses in order to facilitate the simultaneous performance of multiple tasks. Multipurpose objects were promoted to act as ‘bridges’ between distinct domestic regions, while multifunctional spaces and open‐plan interiors collapsed distinctions between such regions. Thus changes in the roles of women within society and the family are shown in this analysis of domestic advice literature to affect the design and layout of the home, and domestic advice books are seen to have promoted ultimately conservative solutions.

Cognitive mechanisms, specificity and neural underpinnings of visuospatial peaks in autism

In order to explain the cognitive and cerebral mechanisms responsible for the visuospatial peak in autism, and to document its specificity to this condition, a group of eight high-functioning individuals with autism and a visuospatial peak (HFA-P) performed a modified block-design task (BDT; subtest from Wechsler scales) at various levels of perceptual cohesiveness, as well as tasks tapping visuomotor speed, global perception, visual memory, visual search and speed of visual encoding. Their performance was compared with that of 8 autistics without a visuospatial peak (HFA-NP), 10 typically developing individuals (TD) and 8 gifted comparison participants with a visuospatial peak (TD-P). Both HFA-P and HFA-NP groups presented with diminished detrimental influence of increasing perceptual coherence compared with their BDT-matched comparison groups. Neither autistic group displayed a deficit in construction of global representations. The HFA-P group showed no differences in performance level or profile in comparison with the gifted BDT-matched [i.e. higher full-scale IQ (FSIQ)] group, apart from locally oriented perception. Diminished detrimental influence of perceptual coherence on BDT performance is both sensitive and specific to autism, and superior low-level processing interacts with locally oriented bias to produce outstanding BDT performance in a subgroup of autistic individuals. Locally oriented processing, enhanced performance in multiple tasks relying on detection of simple visual material and enhanced discrimination of first-order gratings converge towards an enhanced functioning and role of the primary visual cortex (V1) in autism. In contrast, superior or typical performance of autistics in tasks requiring global processing is inconsistent with the global-deficit-driven Weak Central Coherence hypothesis and its neurobiological magnocellular deficit counterpart.

Adaptive Task Prioritization in Aging: Selective Resource Allocation to Postural Control Is Preserved in Alzheimer Disease

With age, the performance of multiple tasks decreases, a pattern exaggerated in Alzheimer disease (AD). At the same time, recent research, based on adaptive theories of healthy aging, indicates a preference of older adults to allocate resources toward tasks of higher immediate value (e.g., postural control). This study investigated whether such models also hold for pathologic cognitive aging. Using a dual-task paradigm, the authors combined a working memory with a postural control task under easy and difficult conditions in patients with AD, older adults, older adults low on performance on a cognitive marker test, and young adults (N = 40). Participants repeatedly performed a cognitive and a postural control task both simultaneously and in isolation over the course of eight sessions. Consistent with earlier studies on divided attention in age and AD, the authors found large dual-task performance decrements with age and more so in AD. When not challenged, patients with AD showed large performance decrements under dual-task conditions in both postural control and working memory. With increasing difficulty in the postural control task, however, older adults, and more so patients with AD, maintained a high level of functioning in postural control, as compared with working memory. The findings indicate that the theory of selective optimization with compensation extends to pathologic aging and have broad implications for models of dual-task performance and executive control in aging and AD.

The Multiple Tasks Test as a predictor of falls in older adults

Falls are among the most common and serious problems facing the elderly. The Berg Balance Scale (BBS) is the gold standard in measuring falls risk. With higher functioning elders, a ceiling effect is often evidenced using the BBS. The purpose of this study was to determine if the Multiple Tasks Test (MTT) when used in high functioning community dwelling elderly correlated with the BBS. Secondly, this study assessed the unidimensionality of the MTT. If a relationship existed between the performance of multiple tasks and the potential loss of balance resulting in falls, then the MTT would be more appropriate than the BBS at predicting falls in higher functioning individuals. Twenty-two independent community dwelling older adults were tested using both the MTT and the BBS on the same day at a senior center. Correlations between the BBS and the MTT ranged between -0.765 and -0.79. The results of the Guttman's scalability analysis were a plus percentage ratio of 0.75 and an index of reproducibility of 0.93. Scales with these values are regarded as having evidence of unidimensionality. All of the MTT tests correlated with the BBS. In addition, the MTT was found to be unidimensional. Although the MTT correlated with the BBS and was found to be a good cumulative measure, it would benefit from continued study to examine quantifiability, validity and reliability. With further refinement and study, the MTT may be useful at discriminating fallers from non-fallers in high functioning older adults.

Signal processing technique for non-invasive real-time estimation of cardiac output by inductance cardiography (thoracocardiography).

Inductance cardiography (thoracocardiography) non-invasively monitors changes in stroke volume by recording ventricular volume curves with an inductive plethysmographic transducer encircling the chest at the level of the heart. Clinical application of this method has been hampered, as data analysis has not been feasible in real time. Therefore a novel, real-time signal processing technique for inductance cardiography has been developed. Its essential concept consists in performance of multiple tasks by several, logically linked signal processing modules that have access to common databases. Based on these principles, a software application was designed that performs acquisition, display, filtering and ECG-triggered ensemble averaging of inductance signals and separates cardiogenic waveforms from noise related to respiration and other sources. The resulting ventricular volume curves are automatically analysed. Performance of the technique for monitoring cardiac output in real time was compared with thermodilution in four patients in an intensive care unit. The bias (mean difference) among 76 paired thoracocardiographic and thermodilution derived changes in cardiac output was 0%; limits of agreement (+/- 2 SD of the bias) were +/- 25%. It is concluded that the proposed signal processing technique for inductance cardiography holds promise for non-invasive, real-time estimation of changes in cardiac output.

Total intravenous anaesthesia: is it worth the cost?

Total intravenous anaesthesia (TIVA) has many advocates and offers potential benefits, yet the direct costs of this technique are commonly greater than those of inhalation-based alternatives. Although many advantages are claimed for TIVA, in reality all modern anaesthetics are effective and have good safety and tolerability profiles, rendering these differences of less importance now than was perhaps once the case. The majority of direct comparisons between inhaled and intravenous anaesthetics have failed to demonstrate significant differences in recovery times, yet they have consistently shown greater direct costs associated with intravenous propofol anaesthesia. It is commonly believed that indirect costs may be offset by indirect savings achieved through more rapid recovery, reduction in adverse effects and decreased staff workloads. In some cases, these differences in outcome have not been observed, while in many where they have, indirect savings are only theoretical. Reductions in recovery time and nursing workload will only result in savings if fewer nurses are required or if the existing ones can be paid for fewer hours. Salary arrangements, peak demand for patient care, performance of multiple tasks in parallel and limitations in time accounting methodology all limit the ability to achieve such savings in reality. Drug wastage also contributes to the cost of anaesthesia and is common to both intravenous and inhaled techniques. With inhaled anaesthesia, wastage can be reduced by the use of lower fresh gas flows, which has no adverse consequences and may provide potential benefits. With intravenous anaesthesia, reducing drug wastage is difficult and potentially harmful through cross-contamination of drugs between patients. Recently, the cost of propofol has been reduced with the availability of generics, making TIVA a more attractive proposition. The costs of several inhaled anaesthetics have also decreased, however, reducing any relative benefit. Nevertheless, the net result of lowered costs is that all types of anaesthetic drugs, which typically comprise <5% of a hospital pharmacy budget, represent excellent value for money. With few new products in the immediate pipeline and most established drugs already generic or about to lose their patent protection, the expense of anaesthesia is likely to decline even further. Perhaps then we will be able to stop arguing over relatively small differences in cost and choose a technique that, in our own experienced hands, provides the best and safest patient outcomes.

Methylphenidate Effects on Task-Switching Performance in Attention-Deficit/Hyperactivity Disorder

To examine the specificity of methylphenidate effects on the processes that support the ability to rapidly and accurately coordinate the performance of multiple tasks in children with attention-deficit hyperactivity disorder (ADHD). Twenty children with ADHD performed the task-switching paradigm while on and off medication. The paradigm involves switching between two different tasks, discriminating the value of a number presented on a computer screen and deciding how many numbers were present on the screen. The children also performed single-task control conditions. Analyses of variance indicated the medication selectively enhanced the children's ability to rapidly and accurately switch between tasks and to focus attention on the currently relevant response set. This study helps to elucidate the nature of methylphenidate effects on the cognitive processes which support the ability to coordinate the performance of multiple tasks. Medication appears to selectively enhance inhibitory processes which support task-switching.

Dual-task performance in depressed geriatric patients

Older patients suffering from a major depression are often impaired on tasks that require executive control processes. However, a wide variety of executive abilities exist in humans, and it is not clear that all are impaired in depression or that such impairments persist beyond remission of the depression. One executive process that plays a central role in mental operations such as working memory is the ability to co-ordinate the simultaneous performance of multiple tasks. Dual-task performance has been extensively studied in normal subjects but there is little work with depressed patients. The present study examined the performance of depressed ( M age=71.0, S.D.=7.1) and control subjects ( M age=69.3, S.D.=7.0) on two tasks (visual tracking and backward digit span), both when each task was carried out by itself and when the two tasks were carried out simultaneously. Dual-task performance was impaired in depressed patients prior to antidepressant treatment and this impairment persisted even after remission of the depression. These results suggest that, like other executive abilities, the ability to schedule and co-ordinate the conflicting processing demands present in a dual-task situation is impaired in depressed geriatric patients and that this impairment may be a trait effect.

Multiple-Task Performance: A Comparison of Younger and Older Adults

There is considerable disagreement among researchers regarding the psychological mechanisms underlying age-related acquisition and transfer of attentional control in multiple-task environments and effective training strategies. We outline a study conducted to examine the effects of extended practice on the performance of multiple tasks. In the study, five different training strategies (i.e., whole task, dual task, single task, embedded dual task, and embedded single task) were evaluated. The embedded dual- and single-task strategies required emphasis of a dual or single task within whole-task performance, respectively. The results revealed that both younger and older adults improved their multiple-task performance of a wide-ranging, complex set of tasks; however, younger adults consistently outperformed older adults. Except for single-task training, training strategy had little differential effect on younger adults' multiple-task performance. On the contrary, among older adults the most effective training strategies were the whole- and dual-task strategies, which required concurrent-task performance, self-assignment of task priorities, task coordination, and performance strategy development for two or more tasks. Single-task training, overall, was the least effective among the five training strategies. The theoretical and practical implications for these findings are disussed.

The effects of individual time urgency on group polychronicity

Recent work concerning the effects of time on group behavior suggests that individuals’ time‐oriented behaviors may act as a catalyst or pacing mechanism for subsequent group behaviors. Other work suggests that group polychronic behavior (the group’s performance of multiple tasks simultaneously) has significant effects on both individual and group outcomes. In this paper, we examine the relationship between individuals’ time‐oriented behavior and group‐level polychronic behavior. Based on results from a laboratory simulation involving 26 small groups, we conclude that the presence of time‐urgent group members increases group‐level monochronic (versus polychronic) behavior and has a positive effect on groups’ primary task activity.

Computational method for ranking task-specific exposures using multi-task time-weighted average samples

A method is presented for ranking task-specific exposures using time-weighted average samples collected during the performance of multiple tasks. The task ranking can be used for purposes such as prioritizing further assessment or control. No a priori estimates of the individual task concentration distributions are required. Sample concentrations and task-specific concentrations are assumed to be log-normally distributed, and each known sample concentration is modeled as the geometric time-weighted average of the unknown task concentrations. Since the task durations are usually not known, the task time-weights are estimated as a crude fraction of sampling period. Log transformed sample concentrations are aggregated based on the non-occurrence of each task during some samples, resulting in a set of linear equations which are solved to yield estimates of the log-transformed task median concentrations. The performance of the method was tested under a variety of conditions using simulated sample data. The method was found to yield remarkably reliable ranking of task median concentrations, especially for the high exposure tasks, provided that the number of samples was adequate and the task concentration distributions were not highly overlapped. The performance of the method can be easily modeled using simulated data over the range of plausible task concentration distributions for any number of samples and any job scenario. Even under the conservative assumption that some task concentration distributions are highly overlapped, the assigned ranking can be usefully interpreted in the light of the modeling to determine whether a task is relatively high exposure or low exposure.

Computational method for ranking task-specific exposures using multi-task time-weighted average samples

A method is presented for ranking task-specific exposures using time-weighted average samples collected during the performance of multiple tasks. The task ranking can be used for purposes such as prioritizing further assessment or control. No a priori estimates of the individual task concentration distributions are required. Sample concentrations and task-specific concentrations are assumed to be log-normally distributed, and each known sample concentration is modeled as the geometric time-weighted average of the unknown task concentrations. Since the task durations are usually not known, the task time-weights are estimated as a crude fraction of sampling period. Log transformed sample concentrations are aggregated based on the non-occurrence of each task during some samples, resulting in a set of linear equations which are solved to yield estimates of the log-transformed task median concentrations. The performance of the method was tested under a variety of conditions using simulated sample data. The method was found to yield remarkably reliable ranking of task median concentrations, especially for the high exposure tasks, provided that the number of samples was adequate and the task concentration distributions were not highly overlapped. The performance of the method can be easily modeled using simulated data over the range of plausible task concentration distributions for any number of samples and any job scenario. Even under the conservative assumption that some task concentration distributions are highly overlapped, the assigned ranking can be usefully interpreted in the light of the modeling to determine whether a task is relatively high exposure or low exposure.

P3, Positive slow wave and working memory load: a study on the functional correlates of slow wave activity

Parietal positivities of the `slow wave' type are known to emerge after the P300 whenever target detection leads to a complex subsidiary task. Although the functional correlates of these `positive slow waves' (PSW) are not known, it has been suggested that they may index (a) the selection or decision processes, (b) the preparation of the response or (c) the evaluation of its correctness. We investigated whether PSW could be dissociated from each of these putative steps of information processing by means of a paradigm devoid of motor components and needing very long reaction times. In our protocol, target stimuli acted as the triggering signal to perform silently one of 4 different tasks, namely (a) simple updating of a target count; (b) counting backward in threes; (c) simultaneous updating of two items (day of the week and ordinal of the month) and (d) updating of 3 items (the two above plus the month of the year). Reaction times to the same stimuli were obtained in 5 subjects during separate sessions. The different tasks did not modify the latencies of N2 or P3b components, but attenuated the amplitude of P3 as a mirror image of the subjective difficulty scores. A conspicuous parietal PSW appeared in conditions where two or 3 items had to be updated. This PSW developed 1–2 s earlier than the reaction times to the same experiments and could be therefore dissociated from the selection and decision processes. PSW latency was correlated with the number of items to be updated, but not with subjective difficulty. In the present paradigm PSW appeared to index the retrieval of information from working memory; however, in more general terms our results suggest that PSW is a non-specific activity that signals the completion of any synchronized operation immediately following target detection. Our data suggest a functional link between P3 and PSW, also supported by the similarity of their respective scalp topographies. The present paradigm proved to be easy to implement and suitable to study the `executive' functions governing attentional and working-memory control during the performance of multiple tasks.

Restructuring of production and workers' health: a case study

We performed a case study on a company focusing on the form of management and the shop floor workers, in order to identify the possible effects of participant work strategies on workers' health. Data on the company included its history, type of management, and organization of both production and the work process. Data on shop floor workers included age, schooling, perceptions of work, family life, recreation, and self-reported disease history. We concluded that the characteristics of the management model adopted by the company originated from ideas imported from Japan, including flexibilization of production, outsourcing, performance of multiple tasks, and participation in the work process. Workers referred to participation in the work process in an ambiguous tone. Some reported positive effects, like greater freedom and respect, with positive effects on life both inside and outside the workplace. For part of the group studied, the characteristics of the work organization model practiced in the company had negative effects on health, leading them to complain of insomnia, nervousness, work-related dreams, and headaches.

Enhancement of Performance in Multiple Learning Tasks by Corticotropin-Releasing Factor-Binding Protein Ligand Inhibitors

Heinrichs, S. C., E. A. Vale, J. Lapsansky, D. P. Behan, L. V. McClure, N. Ling, E. B. De Souza and G. Schulteis. Enhancement of performance in multiple learning tasks by corticotropin-releasing factor-binding protein ligand inhibitors. Peptides 18 (5) 711–716, 1997.—Evidence favors a role for corticotropin-releasing factor (CRF) in learning and memory processes. A binding protein (CRF-BP) with the ability to inactivate CRF provides a novel target to modulate endogenous levels of CRF. The present studies employed three measures of information processing in rats in order to examine the impact of CRF system activation resulting from administration of CRF-BP ligand inhibitors, which increase levels of “free CRF.” Acquisition of a visual discrimination paradigm and retention of a inhibitory avoidance task were dose dependently facilitated by central administration of a CRF-BP ligand inhibitor. CRF-BP ligand inhibitor treatment also improved performance in an active avoidance paradigm in aged animals. No nonspecific anorexic effects of the active dose of CRF-BP ligand inhibitor were detected in a food intake test. Moreover, the magnitude of in vivo efficacy of the CRF-BP ligand inhibitor peptide in producing a mild increase in motor activity was dissociated from that of a postsynaptic CRF receptor agonist that exerted robust and long-lasting activity increases. Thus, CRF-BP ligand inhibitors appear to elicit generalized learning enhancement effects without mimicking the robust nonspecific behavioral actions of a CRF receptor agonist.

Predictive Performance Models and Multiple Task Performance

This symposium presents five models that predict how performance of multiple tasks will interact in complex task scenarios. The models are discussed, in part, in terms of the assumptions they make about human operator divided attention. The different assumptions about attention are empirically validated in a multitask helicopter flight simulation reported in the present paper. It is concluded from this simulation that the most important assumption relates to the coding of demand level of different component tasks. The potential gains to be made multiple resource assumptions remain uncertain.

Dissociations and dependencies between speed and accuracy: Evidence for a two-component theory of divided attention in simple tasks

Previous work has amply demonstrated divided attention “costs” both in single-task multistimulus visual processing and in performance of multiple simple tasks; however, the relationship between the two has not been clarified. This article postulates two distinct causes: (1) visual processes that commence without delays and proceed simultaneously, but show lingering mutual interference dependent upon complexity, and (2) discrete queueing of the response selection stage. The first has resource-like properties, while the second has bottleneck-like properties. Either or both can generate performance costs observed in any particular situation, accounting for a variety of previous results. To test this theory, the effects of stimulus onset asynchrony (SOA) on accuracy and speed in performing dual choice tasks were examined. The first two experiments involved a choice response to a tone as a first task, and a second task requiring complex perceptual decisions (digit identification or conjunction search) with masked displays and unspeeded second responses. Reducing the SOA had negligible effects upon second-task accuracy, and performance in the two tasks was virtually independent. However, when speeded manual (Exp. 3) or vocal (Exp. 4) responses were required on the same second task, dramatic interference was observed, with strong positive dependencies between reaction times (RTs) on the two tasks. When both tasks involved complex visual displays, SOA reductions produced dramatic interference, but no dependencies between performance, whether the first task involved a speeded (Exp. 5) or unspeeded (Exp. 6) response. The results reject pure late-selection accounts and general capacity sharing models, and support the two-component theory. They also suggest that standard use of the term “attention,” suggesting a single resource or mechanism, is highly misleading.