Multiple Task Environment Research Articles

How Does Technical Change Affect Worker Productivity in a Multiple-Task Environment?

How Does Technical Change Affect Worker Productivity in a Multiple-Task Environment?

Effects of social stress on performance and strain in complex multiple task environments

While stress has been an important research area in the field of ergonomics, research on social stress and on the combination of stressors is largely lacking. This study examined the effects of social stress on psychological and physiological strain and performance. As an exploratory research question we looked at the combined effects of social stress and noise. Fifty-one male student participants were tested for 2 h using a computer-based simulation of a process control environment with multiple tasks. Social stress (TSST) and noise (80 dB) were varied experimentally. During the task, we repeatedly measured primary and secondary task performance, subjective strain, and psychophysiological strain (cortisol, heart rate). We found a main effect of social stress on physiological strain, both on cortisol and heart rate, but no main effects of social stress on subjective strain and performance. These results suggest that maintaining performance under stress comes at the cost of physiological strain. Practitioner summary: Although the presence of social stress is common at work, little experimental work has been done. Our experiment provides empirical evidence for negative effects of social stress on physiological stress responses while subjective strain and performance decrements could not be detected. Abbreviations: ANOVA: analysis of variance; b/min: beats per minute; CAMS: cabin air management system; CO2: carbon dioxide; dB: decibel; Df: degrees of freedom; ECG: electrocardiography; h: hours; Hz: hertz; M: mean; min: minutes; N: sample size; nmol/l: nanomol per liter; O2: oxygen; pm: post meridiem; SD: standard deviation; SE: standard error; sec/s: seconds; TSST: trier social stress test

Strategic attention and decision control support prospective memory in a complex dual-task environment

Human performance in complex multiple-task environments depends critically on the interplay between cognitive control and cognitive capacity. In this paper we propose a tractable computational model of how cognitive control and capacity influence the speed and accuracy of decisions made in the event-based prospective memory (PM) paradigm, and in doing so test a new quantitative formulation that measures two distinct components of cognitive capacity (gain and focus) that apply generally to choices among two or more options. Consistent with prior work, individuals used proactive control (increased ongoing task thresholds under PM load) and reactive control (inhibited ongoing task accumulation rates to PM items) to support PM performance. Individuals used cognitive gain to increase the amount of resources allocated to the ongoing task under time pressure and PM load. However, when demands exceeded the capacity limit, resources were reallocated (shared) between ongoing task and PM processes. Extending previous work, individuals used cognitive focus to control the quality of processing for the ongoing and PM tasks based on the particular demand and payoff structure of the environment (e.g., higher focus for higher priority tasks; lower focus under high time pressure and with PM load). Our model provides the first detailed quantitative understanding of cognitive gain and focus as they apply to evidence accumulation models, which – along with cognitive control mechanisms – support decision-making in complex multiple-task environments.

Diversity Management in International Supply Chains: Strategies for Effectiveness

Managing diversity is the hallmark of an international business. International organizations deal with diversity in multiple task environments: culture, communication, operating, technology and supply chain. International organizations are integrated with global and host country local economies and systems. They need to continuously improve the supply chain effectiveness of their global operations to further their competitive position. The effective management of diversity will improve supply chain performance in procuring services, raw materials, components and sub-assemblies.

The Effects of Experience and Strategy on Visual Attention Allocation in an Automated Multiple-Task Environment

Operators and users interacting with computer environments often have to deal with multiple tasks at once, responding to each in series. Diagnostic automation, that is, automation that alerts users when and where to look, has been suggested to support the unique challenges of multiple task environments: activating tasks, switching between tasks, and tasks interfering with each other. Automation is not always reliable, however. Because of the common interaction with novel systems and the importance of training, the Simultaneous Task Environment Platform program—a multiple-task environment—was developed to understand the effects of experience on interaction with these automation-supported systems, as well as what strategies were developed. It was found that participants became more efficient with experience only when they interacted with higher reliability automation. Furthermore, the strategies participants developed focused on the differences between tasks and patterns across those tasks. Automated systems training should be sure to employ these findings.

Human performance in a multiple-task environment: Effects of automation reliability on visual attention allocation

Diagnostic automation has been posited to alleviate the high demands of multiple-task environments; however, mixed effects have been found pertaining to performance aid success. To better understand these effects, attention allocation must be studied directly. We developed a multiple-task environment to study the effects of automation on visual attention. Participants interacted with a system providing varying levels of automation and automation reliability and then were transferred to a system with no support. Attention allocation was measured by tracking the number of times each task was viewed. We found that participants receiving automation allocated their time according to the task frequency and that tasks that benefited most from automation were most harmed when it was removed. The results suggest that the degree to which automation affects multiple-task performance is dependent on the relative attributes of the tasks involved. Moreover, there is an inverse relationship between support and cost when automation fails.

Exploring Strategy Use in a Multiple-Task Environment: Effects of Automation Reliability and Task Properties

Automated aids are often provided to assist human operators in multitasking, high-workload situations. Introducing automation can reduce task demands and improve human performance. If the automation is not perfectly reliable, operators have to strategically operate the system along with automated aids. As a part of an experiment investigating attention allocation and automation, 60 participants’ subjective strategy reports were analyzed to understand how task properties (e.g., frequency, criticality) and automation reliability affect operators’ strategy use. Given different levels of automation reliability, participants developed both automation-dependent and automation-independent strategies to accomplish the tasks. Some strategies (i.e., following a pattern) were significantly correlated with overall task performance. Top performers expressed preferences for different strategies compared to worst performers. This study provided insights into how operators naturally develop and use strategies when interacting with automation.

Cooperative path planning and task assignment for unmanned air vehicles

This article presents a review and a novel approach to the decentralized path planning and task assignment for multiple cooperative unmanned air systems, in multiple target, and multiple task environment. The vehicles (or agents) may have complete or partial a priori information about the targets that populate the scenario. Each vehicle autonomously computes the cost for servicing each task available at each target using a path planning algorithm, taking into account obstacles, pop-up threats, and weights the total path cost including potential risk areas. Vehicles assign an initial ranking to each task, and then exchange their ranking information with the others. Each agent then updates the ranking of its tasks using a non-linear dynamic programming algorithm that is proven to be stable and to converge to an equilibrium point where each vehicle is assigned to a different task. The ranking dynamics is initially formulated as a continuous time system, and then time-discretized depending on available data, and transmission rate among the network. Stability of the network and independence of steady-state values from the data rate are evaluated analytically, and via simulation.

Effects of Alcohol-A Preliminary to Study to Detect Intoxication-

Physiological parameters were obtained before and after alcohol drinking with subjective drunkenness, mood scores and task performances from nineteen male graduate students. Blood was sampled to measure Blood Alcohol Content (BAC) every 30 minute after drinking and Breath Alcohol Content (BrAC) was also measured. Heart rate increase and HF component of heart rate variability decrease were observed as shown in the responses induced by mental stress. However, a different pattern was shown in Tissue Blood Flow comparing with the responses induced by mental stress and physical stimulus. A reaction tine in a multiple task environment increased after drinking while a simple reaction time was not affected by drinking.

Acquisition and Transfer of Attention Allocation Strategies in a Multiple-Task Work Environment

Payoff effects on strategy development and change were assessed in a synthetic work environment, SYNWORK1. Many work settings require several tasks to be performed concurrently. It is important to know how the strategies used in performing the respective tasks vary with payoffs. Sixty students performed four tasks in SYNWORK1, for which points are received for correct responses and lost for incorrect responses. Individual-task payoffs were varied between participants and were changed after 8 and 12 sessions to examine the effects of a previous strategy on development of a new strategy. Participants were sensitive to initial payoffs and modified their strategies when payoffs changed. However, residual effects of prior payoffs were evident. Payoffs for multiple-task environments need to be explicit, and practice should be provided for strategy development. When payoffs change, strategies adopted reflect current and previous payoffs. The findings can be applied to the design of payoff schedules for multiple-task environments.

Effects of Cumulative Sleep Loss and Two Nights' Recovery Sleep on Multiple-Task Performance

The present study investigated the effects of five days' cumulative sleep restriction and two nights' recovery sleep on multiple-task performance and subjective sleepiness in a controlled laboratory environment. A total of 21 volunteers participated, thirteen in the experimental group and eight in the control group. Compared to the control group, the sleepiness of the sleep-loss group gradually increased over the five days, but returned to the baseline level after an eight hour recovery sleep period. Multiple-task performance declined selectively in the memory, arithmetic and auditory subtasks, while visual monitoring results were not affected. After the eight hour recovery period, the performance of the sleep-restricted participants in the auditory subtask remained low, although the individuals themselves no longer reported sleepiness. Performance in the rest of the tasks returned to the baseline level. Thus the partial cumulative sleep loss selectively impaired cognitive performance in subtasks of a multiple-task environment, which simulated many ordinary working environments. This may be due to the slowing of the cognitive processing during sleep restriction, as well as decline in attention control.

Cognitive diversity and team performance in a complex multiple task environment

This article examines the multiple effects of cognitive diversity in teams operating complex human-machine-systems. The study employed a PC-based multiple-task environment, called the Cabin Air Management System, which models a process control task in the operational context of a spacecraft's life support system. Two types of cognitive diversity were examined: system understanding and team specialization. System understanding referred to the depth of understanding team members were given during training (low-level procedure-oriented vs. high level knowledge-oriented training). Team specialization referred to the degree to which knowledge about system fault scenarios was distributed between team members (specialized vs. non-specialized). A total of 72 participants took part in the study. After having received 4.5 h of training on an individual basis, participants completed a 1-h experimental session, in which they worked in two-person teams on a series of fault scenarios of varying difficulty. Measures were taken of primary and secondary task performance, system intervention and information sampling strategies, system knowledge, subjective operator state, communication patterns and conflict. The results provided evidence for the benefits of cognitive diversity with regard to system understanding. This manifested itself in better primary task performance and more efficient manual system control. No advantages were found for cognitive diversity with regard to specialization. There was no effect of cognitive diversity on intra-team conflict, with conflict levels generally being very low. The article concludes with a discussion of the implications of the findings for the engineering of cognitive diversity in teams operating complex human-machine-systems.

Selective and Nonselective Transfer: Positive and Negative Priming in a Multiple-Task Environment.

Processing of a probe stimulus can be affected either positively or negatively by presenting a related stimulus immediately before it. According to structural accounts, such effects occur because processing of the prime activates or inhibits the mental representation of the probe before it is presented. In contrast, transfer-appropriate processing accounts suggest that success in processing a probe depends on resources made available by earlier experiences of related stimuli. The authors manipulated the similarity between the prime and probe on color, lexical status, and orthographic structure, requiring either lexical decision or color identification on each. The authors observed a complex pattern of positive and negative transfer that cannot easily be explained through activation-inhibition of mental structures. Instead, that pattern provides evidence in favor of transfer-appropriate processing.

Performance in a complex multiple-task environment during a laboratory-based simulation of occasional night work.

A study was carried out to examine the impact of occasional night work on simulated process control using a complex task environment. The 21 student participants were tested during 2 6-hr simulated shifts (daytime and night). In addition to the primary system management task, the simulation allowed measurement of fault diagnosis behavior, monitoring and control actions, and two secondary tasks--alarm reaction time and system status checks (prospective memory)--as well as subjective state. Consistent with predictions from compensatory control theory, night work did not impair system performance, although monitoring and control were reduced (supported by subjective reports of increased use of risky "corner-cutting" strategies). Secondary tasks showed an increase in alarm reaction time during night work, but there was no effect on prospective memory and no clear pattern of change in subjective state. Actual or potential applications of this research include the design of complex systems for nighttime operation.

CAMS as a tool for human factors research in spaceflight

The paper reviews a number of research studies that were carried out with a PC-based task environment called Cabin Air Management System (CAMS) simulating the operation of a spacecraft's life support system. As CAMS was a multiple task environment, it allowed the measurement of performance at different levels. Four task components of different priority were embedded in the task environment: diagnosis and repair of system faults, maintaining atmospheric parameters in a safe state, acknowledgement of system alarms (reaction time), and keeping a record of critical system resources (prospective memory). Furthermore, the task environment permitted the examination of different task management strategies and changes in crew member state (fatigue, anxiety, mental effort). A major goal of the research programme was to examine how crew members adapted to various forms of sub-optimal working conditions, such as isolation and confinement, sleep deprivation and noise. None of the studies provided evidence for decrements in primary task performance. However, the results showed a number of adaptive responses of crew members to adjust to the different sub-optimal working conditions. There was evidence for adjustments in information sampling strategies (usually reductions in sampling frequency) as a result of unfavourable working conditions. The results also showed selected decrements in secondary task performance. Prospective memory seemed to be somewhat more vulnerable to sub-optimal working conditions than performance on the reaction time task. Finally, suggestions are made for future research with the CAMS environment.

Effects of training on short- and long-term skill retention in a complex multiple-task environment

The paper reports the results of an experiment on the performance and retention of a complex task. This was a computer-based simulation of the essential elements of a spacecraft's life support system. It allowed the authors to take a range of measures, including primary and secondary task performance, system intervention and information sampling strategies, mental model structure, and subjective operator state. The study compared the effectiveness of two methods of training, based on low level (procedure-based) and high level (system-based) understanding. Twenty-five participants were trained extensively on the task, then given a 1-h testing session. A second testing session was carried out 8 months after the first (with no intervening practice) with 17 of the original participants. While training had little effect on control performance, there were considerable effects on system management strategies, as well as in structure of operator's mental model. In the second testing session, the anticipated general performance decrement did not occur, though for complex faults there was an increase in selectivity towards the primary control task. The relevance of the findings for training and skill retention in real work environments is discussed in the context of a model of compensatory control.

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.

Electrophysiological, behavioral, and subjective indexes of workload when performing multiple tasks: manipulations of task difficulty and training

This study examined whether alpha event-related desynchronization (ERD) and theta event-related synchronization (ERS) could successfully measure changes in cognitive workload and training while an operator was engaged in a continuous, interactive, control task(s). Alpha 1 (8–10 Hz) ERD, alpha 2 (10–12 Hz) ERD, and theta (3–7 Hz) ERS were determined for a communications event that occurred during multiple task workload conditions or as a single task. Other measures (alpha and theta EEG power, heart rate, respiration, eye blinks, behavioral performance, and subjective workload ratings) were also evaluated. Results showed that alpha 2 EEG, heart rate, behavioral, and subjective measures were sensitive to changes in workload in the multiple tasks. In addition, eye blink rate and behavioral measures were sensitive to training. Alpha ERD and theta ERS were not sensitive to workload and training in our interactive, multiple task environment. However, they were effective indexes of cognitive/behavioral demands within an interactive single task.

Multiple-task performance on a computer-simulated life support system during a space mission simulation

This paper presents an experiment which examined the effects of isolation and confinement during a simulation of a short-term space mission. During the 7-day spaceflight simulation, four Canadian astronauts were tested daily on a 30-min performance task. The task, CAMS (Cabin Air Management System), represents a computer-based simulation of a generic life support system. As a multiple-task environment, it allows the measurement of a wide range of task management variables such as primary and secondary task performance, and system control activities. Measures of subjective state variables were also taken. The results did not show any evidence of serious performance decrements for any crew member. The analysis revealed different adjustment patterns with which crew members responded as a function of mission duration and variations in workload. Among the secondary tasks employed, prospective memory was found to be more sensitive than reaction time to increases in workload. The paper concludes with a discussion of the utility of spaceflight simulations and computer-based simulations of space work.

167 Psychophysiological measures of mental workload in laboratory and flight

This study examined whether alpha event-related desynchronization (ERD) and theta event-related synchronization (ERS) could successfully measure changes in cognitive workload and training while an operator was engaged in a continuous, interactive, control task(s). Alpha 1 (8–10 Hz) ERD, alpha 2 (10–12 Hz) ERD, and theta (3–7 Hz) ERS were determined for a communications event that occurred during multiple task workload conditions or as a single task. Other measures (alpha and theta EEG power, heart rate, respiration, eye blinks, behavioral performance, and subjective workload ratings) were also evaluated. Results showed that alpha 2 EEG, heart rate, behavioral, and subjective measures were sensitive to changes in workload in the multiple tasks. In addition, eye blink rate and behavioral measures were sensitive to training. Alpha ERD and theta ERS were not sensitive to workload and training in our interactive, multiple task environment. However, they were effective indexes of cognitive/behavioral demands within an interactive single task.