The effects of workload history on dual task performance

The purpose of this study was to examine the effects of workload history (specifically sudden workload shifts) on performance. A sample of 204 undergraduates was randomly assigned to either a sudden decrease or increase in workload condition. Participants simultaneously performed a memory search task (i.e., primary task) and an auditory vigilance task (i.e., distracter task), while percent correct was recorded. Separate Repeated Measures ANOVA’s revealed a significant treatment effect for the Medium to Low (F(l, 110) = 274.6, p < .01) and Low to Medium (F(l,92) = 148.3, p < .01) conditions. Results supported previous research suggesting that either a sudden decrease (Medium to Low) or increase (Low to Medium) in workload could be detrimental to performance (Cox-Fuenzalida, 2000). More importantly, this study extends the detrimental effects of workload history to a dual task environment. The authors express their gratitude to the research team from the Personality and Human Performance Lab at the University of Oklahoma for their invaluable assistance in data planning and collection.     

The effects of age and task domain on dual task performance: A meta-analysis

Recent research has provided mixed findings as to whether older adults find dual tasking problematic. Here, we examined whether methodological variations across studies can account for the discrepancies in the literature. Meta-analyses conducted on the results of 34 studies conducted between 1981 and 2003 found a strong overall effect size (d = .68), which indicated a clear age-related dual tasking impairment. However, this effect size was not representative of all the individual studies reported. Subsequent analyses, using an analysis of variance analogue (Hedges & Olkin, 1985), investigated potential moderators responsible for the variability in the effect sizes across studies. These secondary analyses included a comparison of dependent measure used, whether baseline differences in performance had been controlled for, and task domain. Task domain was found to be the critical moderator variable. Notably, tasks with a substantial controlled processing, or motor component showed greater dual task impairment than tasks that were relatively simple or relied on automatic processing.     

Extraversion and task performance: A fresh look through the workload history lens

This study manipulated workload levels and used a technique examining workload history to test Eysenck’s (1967) theory of extraversion. Participants consisted of 71 undergraduates who had been selected from a larger pool that had completed the Eysenck Personality Inventory. Participants performed an auditory vigilance task while percent correct data were recorded. A repeated measures ANOVA was conducted and results indicated that extraverts and introverts respond differently to a sudden decrease in workload level. Specifically, a sudden decrease in workload level resulted in an immediate significant decrement in correct responses for extraverts while the decrement for introverts was minimal. Limitations were discussed and implications for future research were addressed.     

Influence of task demand characteristics on workload and performance

Two experiments are reported that examined the influence of variation in task demand on performance and workload. The first experiment considered how the manipulation of prior level of task demand affected subsequent workload and performance. The second experiment examined the effects on performance and workload of increments in the level of task demand. Results from the first study indicated that prior level of imposed task difficulty did affect response in a manner consistent with a scaling of workload in relation to previous task conditions. The second study demonstrated the primacy of absolute demand level over increments in that demand as influencing operator response. Overall, our results indicate that workload and performance are sensitive to multiple characteristics of the task and not instantaneous demand level alone. These findings are important in explaining why association and dissociation occur between task demand, operator efficiency, and perceived workload in differing performance contexts. The importance of these findings for the aviation psychologist in assessing pilot and operator workload is articulated.     

Involuntary strategy-dependent dual task performance

Previous studies showed that some dual tasks can be performed simultaneously without costs. Yet, a variable SOA between the inputs to such tasks leads to strategic, often involuntary, prioritization of one of the two tasks. Here we explore the boundary conditions for this involuntary or exogenous strategy. In Experiment 1, subjects were initially trained on dual task performance where the input to the two tasks is presented simultaneously (0 SOA). We used two tasks that under such conditions can be performed without costs and indeed subjects displayed perfect sharing of the tasks. Subjects then performed the same two tasks but with a variable SOA (0, 50, 150, 800?ms). This manipulation led to a serial-like performance of the two tasks even in trials with 0 SOA. In Experiment 2, subjects participated in eight sessions. Within each session, they performed in alternation blocks with a fixed 0 SOA and blocks with a variable SOA. Subjects displayed perfect sharing in the pure 0 SOA blocks but performed the two tasks serially in the mixed SOA blocks despite receiving identical instructions. These findings demonstrate that task context is a powerful factor in dual task performance and may lead subjects to involuntarily exhibit dual task costs even in conditions where they can perform the tasks without any costs. Moreover, these findings strongly suggest that costs observed in PRP studies reflect the use of such exogenous strategies rather than a general structural dual task limitation.     

Task-hemispheric integrity in dual task performance

A condition of task hemispheric integrity is predicted to result in a dual task situation when the central processing and response components of each task are associated exclusively with a given cerebral hemisphere. The prediction that this condition will generate more efficient time-sharing is tested in a series of four experiments. In experiment 1 the prediction is confirmed when a spatial (tracking) and verbal (letter memory search) task are time-shared, and the hand assignment to task responses is manipulated. In experiment 2 a spatial variant of the memory search is used instead of the verbal letter search, and hand assignment effects are not obtained, since when two spatial tasks are time-shared an integrity assignment is impossible. Experiment 3 validates the hemispheric lateralization of the two single task variants of the memory search task, while experiment 4 establishes the separate “spatial’ and “verbal” resource demands of the two variants by observing their differential interference with concurrent spatial and verbal tasks.     

The effects of age and task context on Stroop task performance

In this study, we investigated the impact of age and task context on Stroop task performance, using error scores, response latencies, and process dissociation estimates (e.g., Lindsay & Jacoby, 1994). Across three experiments, the findings showed that although older adults were able to evaluate Stroop task demands and modify their representations of task context in response to this knowledge, they were less able to maintain and update these representations on a trial-by-trial basis in tasks with high stimulus uncertainty or ambiguity. Moreover, although there was no age-related decline in the ability to modulate print color information, older adults were consistently less able to control the activation of conflicting word information. Together, these findings suggest that whereas age differences in the Stroop task may be magnified under conditions that promote transient failures to maintain task context, the primary source of these differences seems to be a more enduring decline in the efficiency of processes that are responsible for suppressing the activation of irrelevant lexical information.     

The effects of aging and dual task demands on language production

A digital pursuit rotor task was used to measure dual task costs of language production by young and older adults. After training on the pursuit rotor, participants were asked to track the moving target while providing a language sample. When simultaneously engaged, young adults experienced greater dual task costs to tracking, fluency, and grammatical complexity than older adults. Older adults were able to preserve their tracking performance by speaking more slowly. Individual differences in working memory, processing speed, and Stroop interference affected vulnerability to dual task costs. These results demonstrate the utility of using a digital pursuit rotor to study the effects of aging and dual task demands on language production and confirm prior findings that young and older adults use different strategies to accommodate to dual task demands.     

Musical expertise has minimal impact on dual task performance

Studies investigating effect of practice on dual task performance have yielded conflicting findings, thus supporting different theoretical accounts about the organisation of attentional resources when tasks are performed simultaneously. Because practice has been proven to reduce the demand of attention for the trained task, the impact of long-lasting training on one task is an ideal way to better understand the mechanisms underlying dual task decline in performance. Our study compared performance during dual task execution in expert musicians compared to controls with little if any musical experience. Participants performed a music recognition task and a visuo-spatial task separately (single task) or simultaneously (dual task). Both groups showed a significant but similar performance decline during dual tasks. In addition, the two groups showed a similar decline of dual task performance during encoding and retrieval of the musical information, mainly attributed to a decline in sensitivity. Our results suggest that attention during dual tasks is similarly distributed by expert and non-experts. These findings are in line with previous studies showing a lack of sensitivity to difficulty and lack of practice effect during dual tasks, supporting the idea that different tasks may rely on different and not-sharable attentional resources.     

Changes in spinal excitability during dual task performance

ABSTRACT The authors investigated how the nervous system responds to dual task performance. Because dual tasking is associated with greater postural challenges, it was hypothesized that spinal excitability would be reduced when simultaneously performing 2 tasks. For this experiment, participants maintained a lying or standing posture with or without performing a concurrent cognitive task (i.e., reacting to an auditory tone). Spinal excitability was assessed by eliciting the soleus Hoffmann reflex (H-reflex). Results indicated that the H-reflex was 6.4 ± 2.3% smaller (p = .011) when dual compared to single tasking. The reduced H-reflex amplitude, indicating a depressed spinal excitability, when dual tasking is suggested to reflect a neural strategy that individuals adopt to maintain postural stability when cognitive resources are divided between 2 concurrent tasks.     

The effects of music and task difficulty on performance at a visual vigilance task

Forty subjects performed a visual vigilance task in music or noise and when the task was difficult or easy. Response measures taken were: correct detections, commission errors, detection latencies and d' values. For the difficult version of the task a significant increase in detection latencies was found which music prevented. Broadly similar findings were obtained for correct detections. The results are compared with other studies of detection latency and task difficulty and are discussed in terms of arousal.     

The interactive effects of task complexity and participation on task performance: A field experiment

Goal-setting investigators have suggested that participation in the goal-setting process may be important for both motivational and cognitive reasons; however, goal-setting research has focused almost exclusively on the motivational aspect of participation, while generally ignoring the cognitive aspect. In an attempt to demonstrate the cognitive implications of participation, a field experiment was conducted with 40 computer programmers writing either a simple or a complex program. Half the participants were actively involved in discussing the project and in jointly determining the completion target, while the other half were simply assigned completion times of equivalent difficulty. It was hypothesized that, for complex programs, individuals participating in the discussion process would outperform individuals having assigned targets of similar difficulty. In contrast, for simple programs, it was expected that participation would have no effect on task performance. The data were analyzed using a 2 × 2 ANOVA procedure, and results strongly supported the hypothesized interaction. Discussion centered on the implications of the findings for future research in this area.     

The effects of mental representation on performance in a navigation task

In three experiments, we investigated the mental representations employed when instructions were followed that involved navigation in a space displayed as a grid on a computer screen. Performance was affected much more by the number of instructional units than by the number of words per unit. Performance in a three-dimensional space was independent of the number of dimensions along which participants navigated. However, memory for and accuracy in following the instructions were reduced when the task required mentally representing a three-dimensional space, as compared with representing a two-dimensional space, although the words used in the instructions were identical in the two cases. These results demonstrate the interdependence of verbal and spatial memory representations, because individuals' immediate memory for verbal navigation instructions is affected by their mental representation of the space referred to by the instructions.     

Social influence and sex effects on task performance and task perceptions

A laboratory experiment was conducted to investigate the effects of observer presence and subject sex on both performance quantity and quality, job satisfaction, and task perceptions. Multivariate analysis of covariance (MANCOVA) results demonstrated statistically significant multivariate effects on the performance measures. Significant main effects of observer presence were found for performance quality but not quantity. A significant observer presence x subject sex interaction was found for performance quantity. The results for task perceptions supported the hypothesis that the situational factors would make salient the significance of the task. Main effects of observer presence were found for task significance only. Also there was a significant observer presence x subject sex interaction on perceptions of task significance. No effects were found on job satisfaction, consistent with past research. The results are discussed relative to social facilitation research in the broader context of social influence.     

Effects of jet engine noise and performance feedback on perceived workload in a monitoring task

This study examined the effects of exposure to intermittent jet aircraft noise (70 dBA or 95 dBA maximum intensity) and knowledge of results concerning signal detections (hit-KR) on performance efficiency and perceived workload in a 40-min visual vigilance task. The noise featured a Doppler-like quality in which planes seemed to approach from the monitor's left and recede to the right. Perceptual sensitivity (d') was poorer in the context of noise than in quiet but only in the presence of hit-KR. The lack of noise-related performance differences in the absence of hit-KR most likely reflected a "floor effect" rather than some special relation between noise and feedback. When compared to subjects performing in quiet, those who operated in noise were less able to profit from hit-KR, a result that may reflect the effects of noise on information processing. In addition to its negative effects on signal detectability, noise elevated the perceived workload, as measured by the NASA-TLX. This effect was robust; it was independent of the presence of hit-KR, even though hit-KR generally lowered the overall level of perceived workload. The results provide the initial experimental demonstration that perceived workload is a sensitive measure of the effects of aircraft noise in monitoring tasks.     

A meta-analysis of the n-back task while driving and its effects on cognitive workload

This study investigates the effect of the n-back task on cognitive workload while driving. Results of 20 studies with over 800 participants in total show a moderate to high mean effect size. That means the n-back task varies cognitive load while driving in a substantial matter. Further analysis reveals several moderator variables: experiments conducted in a driving simulator showed larger effect sizes than on-road studies. This effect decreases with increasing driving simulator fidelity. Furthermore, the specific driving task assignment moderates the effect: lane change task scenarios result in higher effects than other situations. Regarding the different measurement methods of cognitive workload, subjective questionnaires seem to have very high sensitivity. In contrast, n-back performance measures, detection response task measures, and physiological measurements result in moderate effect sizes, and driving performance measures show reduced sensitivity. Regarding different implementations of the n-back task itself, surprisingly, no moderators are found. Overall, the findings highlight the suitability of the n-back task as a method of inducing cognitive load in transportation research. The moderator analysis gives an overview of different methodological designs and how these designs will affect effect sizes.     

The effects of dialogue-based task allocation on system performance in a computer-aided air traffic control task

The present study investigated dialogue-based human-computer task allocation. Five levels of allocation mode, four command strategies and a control condition, were examined in a high-task-load situation using a Latin square design. Five male participants acted as controllers in a simplified representation of an air traffic control system, sharing their task with a computer controller. Performance measures were metered on-line, and subjective ratings were recorded between trials. There were significant differences among the groups in the percentage of planes landed by the human-computer system, the total number of commands executed, and the number of allocation commands used. Other variables suggested for further study include comparisons of input mode, dialogue-initiation style, and degraded performance levels of the computer controller.     

Time-pressure effects on performance in a base-rate task

Researchers assume that time pressure impairs performance in decision tasks by invoking heuristic processes. In the present study, the authors inquired (a) whether it was possible in some cases for time pressure to improve performance or to alter it without impairing it, and (b) whether the heuristic invoked by base-rate neglect under direct experience can be identified. They used a probability-learning design in 2 experiments, and they measured the choice proportions after each of 2 possible cues in each experiment. In 1 comparison, time pressure increased predictions of the more likely outcome, which improved performance. In 2 comparisons, time pressure changed the choice proportions without affecting performance. In a 4th comparison, time pressure hindered performance. The choice proportions were consistent with heuristic processing that is based on cue matching rather than on cue accuracy, base rates, or posterior probabilities.     

The effects of sex differences and evaluation on task performance and aspiration

An investigation was conducted of how evaluation differentially affects the performance and aspiration for future performance of 118 high school boys and girls. Subjects were selected to fit into either a superior or average intelligence group. In the high evaluation condition, subjects were instructed that their intelligence was being evaluated in anagram and visual-motor tasks they performed, while those in the low evaluation condition were instructed that the two tasks were being correlated. It was hypothesized that on a highly evaluated task, girls, when compared to boys, would show greater performance debilitation and would have lower aspirations for future performance. Although sex differences were found in performance debilitation and aspiration for future performance, they were not all in the predicted directions. Girls were equally debilitated in anagram performance under both evaluation conditions, while boys were debilitated in anagram performance only under high evaluation. When both boys and girls demonstrated a performance debilitation on the anagram task, their performance declined approximately 10%. No sex differences in performance were found on the visual-motor task. On both tasks, girls' aspirations were significantly affected by evaluation condition. The girls averaged 89% choosing the more difficult task in the low evaluation condition. Evaluation condition had no significant effect on aspiration for boys on either task. Intelligence showed no significant relationships.