Different Levels Of Workload Research Articles

Attention Orienting in Augmented Reality Environments: Effects of Multimodal Cues

The accuracy and efficiency of visual, auditory, and tactile cues to orient attention were tested under different levels of workload. Nineteen participants took part in an experiment in which they performed a visual, auditory, or tactile cueing task under both low and high workload conditions. Results showed that under high workload, both visual cues alone and tactile cues alone improved target detection accuracy. In the low workload condition, perceived workload estimates were lower when tactile cues were present than when absent. These results indicate the benefits of both visual and tactile cues in target detection tasks. These findings have implications for training, systems design, and human performance assessment.

Measuring Distraction: Task Duration and the Lane-Change Test (LCT)

Considerable research activity (e.g., HASTE, CAMP, ADAM projects) is currently focused on producing protocols for assessing the distraction potential of in-vehicle tasks and devices. The Lane Change Test (LCT) is a relatively simple and low cost standardized test scenario designed for measuring driver distraction. The purpose of the present study was to evaluate the LCT's ability to discriminate between different secondary tasks with different levels of workload. The LCT was used to assess the driving performance of twenty-one drivers while they performed typical navigation tasks, Point of Interest (POI) Entry and Destination Entry, each with a low and high workload version. The experimental set up included a steering wheel, foot pedals, monitor, computer and navigation system, all off the shelf. The results indicated that the LCT is a sensitive measure of driver distraction. The participants showed greater mean deviation in lane change path when driving while performing a secondary task (i.e., calibration and navigation tasks) than when driving without performing a secondary task (i.e., baseline). When driving while performing secondary tasks, drivers showed differences in lane change path deviations as a function task type and task complexity. These differences were also reflected in participants mean task time to complete the secondary tasks. The present research provides evidence that the LCT metric of lane change path deviations discriminates between different types and complexity levels of secondary tasks, and that these differences are a function of time taken to complete the secondary tasks.

Workload variation, intrinsic risk and utility in a simulated air traffic control task: Evidence for compensatory effects

Air traffic control operations provide a potential example of risk homeostasis theory (RHT) in a non-transportational domain. This paper addresses the issue of whether reductions in intrinsic risk can be negated by behavioural adjustments of operators. Following variations in mental workload, previous studies have suggested that air traffic controllers appear to adapt to changing demands through more active or more effective strategic control of performance. This effortful compensatory control of performance has the consequence of eliminating what would otherwise be concomitant variations in accident loss. However, most of the empirical support for this proposition is taken from observational studies in which the relative occurrence of different levels of workload is not controlled. Using a simulated air traffic control task, a study is reported here in which conditions of low, moderate and high levels of mental workload are presented in equal duration to participants. The findings indicate that number of errors differed significantly across these conditions of mental workload which is contrary to what RHT would predict. Evidence is found for a general adaptation (or strategy switching) in response to different levels of workload. This supports earlier work in indicating that behavioural adjustments may not be of sufficient magnitude to restore previously existing levels of safety. However, on a notional measure of extrinsic compensation, participants did respond differently according to workload, thus lending limited support to RHT's prediction that utility and intrinsic risk should act in a multiplicative way to form a statistical interaction.

Comparison of Four Subjective Workload Rating Scales

Four subjective workload scales were compared along four dimensions: sensitivity, operator acceptance, resource requirements, and special procedures. The scales were the Modified Cooper-Harper scale, the National Aeronautics and Space Administration Task Load Index (TLX), the Overall Workload (OW) scale, and the Subjective Workload Assessment Technique. Three U.S. Army systems were studied for potential workload concerns. Data from five different studies on the three systems were compared along the aforementioned four dimensions. Results indicate that all four scales are acceptable tools and are sensitive to different levels of workload. However, TLX and OW are consistently superior when considering sensitivity, as measured by factor validity, and operator acceptance. This research is an example of a systematic approach for examining human factors measurement tools.

Planning and Scheduling in Flight Workload Management

A closed loop adaptive model for workload has been proposed by Hart and Wickens (1990) in which planning and scheduling activities contribute to the increase or diminution of workload the operator may experience. Of relevance to this model is people's ability to estimate how much time they need to complete a task, their ability to prioritize the tasks to be performed, and their ability to schedule those tasks on time. Thirty pilots flew three ILS approaches under different levels of workload. The data indicates that the increase in workload affected flight performance as well as the planning and scheduling of tasks with different levels of prioritization. This level of prioritization closely approximated the flight instructor's and the subjects' subjective ratings of the degree of importance of each task. It is also suggested that overconfidence in time estimation may depend on the task involved. Finally, the data is discussed in terms of its implication to a closed loop adaptive model of workload.

Diagnosis of vasospastic angina by analysis of heart rate response to exercise: effects of different levels of work load.

To examine alterations in control functions of the heart, which may account for the pathophysiologic conditions precipitating coronary arterial spasm, heart rate response to exercise in vasospastic angina was evaluated by using our previously developed method of frequency analysis. We also examined the effects of three different levels of work load on the heart rate response to treadmill exercise in 9 patients with vasospastic angina and 7 normal controls: stage 1 (2.5 Km/h, 10%), stage 3 (4.5 Km/h, 10%), and stage 5 (5.5 Km/h, 14%). The transfer function of heart rate control in vasospastic angina was characteristically different from that in normal controls: lower gain and more delayed phase angle of the system. Although this abnormality was observed in every test at 3 different levels of work load, the abnormality was more striking in tests at lower levels of work load: stage 1 or 3. The moderately light exercise test at stage 3 is most suitable as a test for detecting abnormal heart rate response to exercise in vasospastic angina because the exercise test at stage 1 had a poor S/N ratio.