Memory overload or expectancy effect? 'Hysteresis' revisited

Transitions Between Low and High Levels of Mental Workload can Improve Multitasking Performance

OCCUPATIONAL APPLICATIONS Complex and dynamic environments including military operations, healthcare, aviation, and driving require operators to transition seamlessly between levels of mental workload. However, little is known about how the rate of an increase in workload impacts multitasking performance, especially in the context of real-world tasks. We evaluated both gradual and sudden workload increases in the dynamic multitasking environment of an Unmanned Aerial Vehicle (UAV) command and control testbed and compared them to constant workload. Workload transitions were found to improve response time and accuracy compared to when workload was held constant at low or high. These results suggest that workload transitions may allow operators to better regulate mental resources. These findings can also inform the design of operations and technology to assist operators' management of cognitive resources, which include negating the adverse effects of vigilance decrements during low workload periods and data overload during high workload periods.

Cognitive Workload and Workload Transitions Elicit Curvilinear Hemodynamics During Spatial Working Memory

Adaptive training and workload management have the potential to drastically change safety and productivity in high-risk fields-including, air-traffic control, missile defense, and nuclear power-plant operations. Quantifying and classifying cognitive load is important for optimal performance. Brain-based metrics have previously been associated with mental workload. Specifically, attenuation of prefrontal activity has been linked to cognitive overload, a cognitive load state associated with degraded task performance. We hypothesized that a similar nonlinearity would be observed for cognitive underload. When underload and overload effects are combined, they should form a cubic function in lateral prefrontal cortex as a function of working memory load. The first of two studies assessed the relationships between spatial working memory load with subjective, behavioral and hemodynamic measures. A cubic function was observed in left dorsolateral prefrontal cortex (LDLPFC; Brodmann's Area 46) relating working memory load to changes in oxygenated hemoglobin (HbO). The second, two-part study tested the effects of workload transitions to different cognitive load states. Part-one replicated the effects observed in study one and identified transition points for individual performers. Part-two assessed the effects of transitioning to different cognitive load states. Cognitive load state transitions caused a deviation between behavioral measures and induced a significant change in the cubic function relating LDLPFC HbO and working memory load. From these observations, we present a hypothesis associating workload transitions with the disruption of cognitive process integration.

Examining Functional Spatial Perception in 10-Year-Olds and Adults

This study examined a specific type of spatial perception, functional spatial perception, in 10-year-old children and adults. Functional spatial perception involves anticipating actions made with objects to fulfill a function, or, in this case, fitting objects through openings. We examined accuracy, sensitivity, and consistency in participants' abilities to adjust a window to the smallest opening through which a small wooden cube would fit. Success at this task requires accounting for the dimensions of both the object and the opening. In life circumstances, poor decisions at similar tasks may result in injury, frustration, or property damage. As much previous work in this area included very young children and adults, we sought to determine whether older children (10-year-olds) would show adult-like skills. Ten-year-old participants were as equally accurate and sensitive as adults, and both groups left a safety margin in performing this task; but we found that adults made more consistent judgments than 10-year-olds. There are developmental implications for these findings, given daily real-life needs to accurately gauge functional spatial relations and navigate objects in real life.

Hysteresis in Mental Workload and Task Performance: The Influence of Demand Transitions and Task Prioritization

OBJECTIVE

We examine how transitions in task demand are manifested in mental workload and performance in a dual-task setting.

BACKGROUND

Hysteresis has been defined as the ongoing influence of demand levels prior to a demand transition. Authors of previous studies predominantly examined hysteretic effects in terms of performance. However, little is known about the temporal development of hysteresis in mental workload.

METHOD

A simulated driving task was combined with an auditory memory task. Participants were instructed to prioritize driving or to prioritize both tasks equally. Three experimental conditions with low, high, and low task demands were constructed by manipulating the frequency of lane changing. Multiple measures of subjective mental workload were taken during experimental conditions.

RESULTS

Contrary to our prediction, no hysteretic effects were found after the high- to low-demand transition. However, a hysteretic effect in mental workload was found within the high-demand condition, which degraded toward the end of the high condition. Priority instructions were not reflected in performance.

CONCLUSION

Online assessment of both performance and mental workload demonstrates the transient nature of hysteretic effects. An explanation for the observed hysteretic effect in mental workload is offered in terms of effort regulation.

APPLICATION

An informed arrival at the scene is important in safety operations, but peaks in mental workload should be avoided to prevent buildup of fatigue. Therefore, communication technologies should incorporate the historical profile of task demand.

A multilevel approach to relating subjective workload to performance after shifts in task demand

OBJECTIVE

The aim of this laboratory experiment was to demonstrate how taking a longitudinal, multilevel approach can be used to examine the dynamic relationship between subjective workload and performance over a given period of activity involving shifts in task demand.

BACKGROUND

Subjective workload and conditions of the performance environment are oftentimes examined via cross-sectional designs without distinguishing within-from between-person effects. Given the dynamic nature of performance phenomena, multilevel designs coupled with manipulations of task demand shifts are needed to better model the dynamic relationships between state and trait components of subjective workload and performance.

METHOD

With a sample of 75 college students and a computer game representing a complex decision-making environment, increases and decreases in task demand were counterbalanced and subjective workload and performance were measured concurrently in regular intervals within performance episodes. Data were analyzed using hierarchical linear modeling.

RESULTS

Both between- and especially within-person effects were dynamic. Nevertheless, at both levels of analysis, higher subjective workload reflected performance problems, especially more downstream from increases in task demand.

CONCLUSION

As a function of cognitive-energetic processes, shifts in task demand are associated with changes in how subjective workload is related to performance over a given period of activity. Multilevel, longitudinal approaches are useful for distinguishing and examining the dynamic relationships between state and trait components of subjective workload and performance.

APPLICATION

The findings of this research help to improve the understanding of how a sequence of demands can exceed a performer's capability to respond to further demands.

The Impact of Sudden Events and Spatial Configuration on the Benefits of Prior Information to Situation Awareness and Performance

Having task-relevant information prior to performing the task can improve performance and situation awareness. This study examined the impact of spatial complexity (apartment vs. office buildings) and the presence of sudden events on the benefits of having information prior to fighting fire in a burning building. Performance of an urban firefighting team (finding victims) and situation awareness (SA) were measured in a lab simulation study. Findings show that having complete prior information did improve SA, performance was better in the office building, and performance deteriorated after a sudden event. However, an in-depth examination of the findings suggests that characteristics of the spatial configuration and the presence of sudden events influence the benefits of having prior information.

The effect of prior task loading on mental workload: an example of hysteresis in driving

OBJECTIVE

This study examined how transitions in task demand during a driving and navigation task manifested themselves as delayed adaptation in driver mental workload.

BACKGROUND

A delayed reaction to changes in demand levels, termed hysteresis, has been identified in a number of settings. However, little research has specifically examined the driving task for hysteresis effects.

METHOD

A total of 32 drivers completed drives while using a navigation system that would fail within the drive. Subjective mental workload was recorded prior to and following system failure as well as at the conclusion of the drive.

RESULTS

Results indicated that a gradual reduction in overall mental workload across trials and a lagged recovery to reduction in task demand was present within trials. Analysis of the mental workload subscales within trials indicated that this effect was produced by the mental effort component of workload.

CONCLUSION

A moderate hysteresis effect is present in mental workload transitions within the driving task. Although subjective mental workload decreases across trials, the magnitude of the lagged recovery within trials remains unchanged.

APPLICATION

Scaling of in-vehicle information is beneficial with respect to driver mental workload. Display and communication technologies designers should consider not only the immediate task demand but also the driver's task demand history when determining what and how to provide information.

Effect of workload history on task performance

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.