Effect of Workload History on Task Performance

Abstract

Objective: This study investigated the effects of workload history (specifically, sudden shifts in workload) on performance. Background: In 1993 the National Research Council identified workload transition as an important concern for human factors researchers. The study of workload history suggests that what an individual has been doing prior to a point in time has an effect on subsequent performance. One trend emerging from workload history studies is that a general decrement in performance is most likely to occur following a decrease in task demand. Method: The 198 participants were randomly assigned to a high-to-low or low-to-high condition. Participants performed a version of the Bakan Vigilance Task while correct responses, response times, and total errors were recorded. Results: Results supported previous research suggesting a workload decrease results in a performance decrement. More importantly, this study reports that either a sudden increase or decrease could lead to a loss in accuracy and a slowing of response time in a longer time course. Conclusion: An explanation of the decrement is offered in terms of adaptation models. In addition, a follow-up study suggested that the decrement is a result of something inherent in the workload shift rather than an effect of fatigue. Application: Workload history (more specifically, a workload shift) has significant implications for many work environments. These implications are particularly salient in occupations where individuals are confronted with varying levels of workload demand, especially safety-sensitive occupations.

The Relationship Between Workload and Performance in Air Traffic Control: Exploring the Influence of Levels of Automation and Variation in Task Demand

“…Previous research has infrequently considered transitions of task demand in an applied environment. Findings are consistent with the description of workload history effects [8], and that equivalent task demand periods can elicit different experiences for a human operator depending on what precedes the time of rating. Attentional resource and arousal theories appear to support interpretation of the results.…”

“…In addition, this permitted an extension of previous studies that had focused on the comparison of workload and performance for one transition period (e.g. [8]). …”

“…These transitions can be expected by the controller, such as when traffic load changes based on the time of day or known activities in surrounding sectors, or unexpected, for example, through increased complexity resulting from an emergency situation. Transitions may also be gradual or sudden [8]. Controllers, therefore, have to remain vigilant at all times when they are 'on position' to make sure they are aware of events as they build, even if the transition is sudden.…”

“…[10]) have found that performance on vigilance tasks was influenced by a low-to-high demand transition or high-to-low demand transition (e.g. [8]). Task demand and workload transition research specific to an ATC environment is particularly underrepresented.…”

A Multilevel Approach to Relating Subjective Workload to Performance After Shifts in Task Demand

“…Consequently, a transitional state, such as overload, reflects dynamic instability, which is manifested in performance vis-à-vis (a) increases in response times and errors; (b) greater variability in performance; (c) fewer tasks completed per unit time; (d) high-risk, low-effort decision strategies; and (e) rule-based control (Hockey, 1993;Holding, 1983;Messick Huey & Wickens, 1993;Rasmussen, 1986). Alternatively, decreases in task demand or more modest periods of task demand should not adversely affect the level of resources available, such that subjective workload would not represent capabilities being exceeded (Cox-Fuenzalida, 2007). That is, individuals are not likely to transition from a comfort zone characterized by a state of dynamic stability to a state of dynamic instability (Hancock & Warm, 1989).…”