Measures Of Mental Workload Research Articles

Investigating the Use of Two Low Cost Eye Tracking Systems for Detecting Pupillary Response to Changes in Mental Workload

Eye tracking technologies are being utilized at increasing rates within industry and research due to the very recent availability of low cost systems. This paper presents results from a study assessing two eye tracking systems, Gazepoint GP3 and Eye Tribe, both of which are available for under $500 and provide streaming gaze and pupil size data. The emphasis of this research was in evaluating the ability of these eye trackers to identify changes in pupil size which occur as a function of variations in lighting conditions as well as those associated with workload. Ten volunteers participated in an experiment in which a digit span task was employed to manipulate workload as user’s fixated on a monitor which varied in background luminance (black, gray and white). Results revealed that both systems were able to significantly differentiate pupil size differences in high and low workload trials and changes due to the monitor’s luminance. These findings are exceedingly promising for human factors researchers, as they open up the opportunity to augment studies with non-obtrusive, streaming measures of mental workload with technologies available for as little as $100.

Determination of nurses' mental workloads using subjective methods

To adapt the National Aeronautics and Space Administration Task Load Index scale into Turkish, to determine the nurses' mental workload using subjective methods and to identify the factors affecting the mental workloads of nurses. As the concept of safety gains prominence in healthcare services, the determination of employees' mental workloads using subjective methods is considered important in preventing errors caused by employees. Methodological and descriptive design. The population of the study consisted of a total of 1900 nurses working at three hospitals and a dentistry faculty hospital affiliated with a public university in Istanbul. The sample of the study consisted of 1266 nurses who agreed to participate in the study (the rate of return was 66·6%). Language and content validity and reliability measurements were performed to adapt the National Aeronautics and Space Administration Task Load Index into Turkish, which was used as the data collection tool. It was found that the mean total mental workload score of the nurses was 80·48 (SD 11·76), and the weighted score of mental workload was 83·7. While the highest mean score was obtained on the subscale of mental demand (88·08, SD 16·12), the lowest mean score was obtained on the subscale of frustration (54·52, SD 29·96). The mean total mental workload score of the nurses showed a significant difference according to the units in which the nurses worked. The mean mental workload scores of nurses working at hospitals within the scope of the study were higher than the results of other studies. It is recommended that nurse managers perform mental workload measurements of nurses and compare the results with the quality indicators observed in units to determine and employ a labour force that is qualified for the profession and that may benefit more effectively from human resources.

Research on the application of the improved genetic algorithm in the electroencephalogram-based mental workload evaluation for miners

Electroencephalogram is the electrical phenomena in the cerebral cortex or the scalp surface due to the electrophysiological activity of brain cells. Electroencephalogram has great theoretical and practical significance in measuring mental workload of people. More precise electroencephalographic is a precondition to study mental workload of miners. In this article, based on the actual situation of the electroencephalographic measurement of miners, the particle swarm optimization is introduced to improve the standard genetic algorithm, and put forward a combined method integrating the genetic algorithm with particle swarm optimization for achieving electroencephalogram-based measures of miners' mental workload. Moreover, the MATLAB simulation platform is used for simulation testing. Testing results prove the effectiveness of the combined method.

A Simple(r) Tool For Examining Fixations

This short paper describes an update of A Simple Tool For Examining Fixations (ASTEF) developed for facilitating the examination of eye-tracking data and for computing a spatial statistics algorithm that has been validated as a measure of mental workload (namely, the Nearest Neighbor Index: NNI). The code is based on Matlab® 2013a and is currently distributed on the web as an open-source project. This implementation of ASTEF got rid of many functionalities included in the previous version that are not needed anymore considering the large availability of commercial and open-source software solutions for eye-tracking. That makes it very easy to compute the NNI on eye-tracking data without the hassle of learning complicated tools. The software also features an export function for creating the time series of the NNI values computed on each minute of the recording. This feature is crucial given that the spatial distribution of fixations must be used to test hypotheses about the time course of mental load.

A Simple(r) Tool For Examining Fixations

This short paper describes an update of A Simple Tool For Examining Fixations (ASTEF) developed for facilitating the examination of eye-tracking data and for computing a spatial statistics algorithm that has been validated as a measure of mental workload (namely, the Nearest Neighbor Index: NNI). The code is based on Matlab® 2013a and is currently distributed on the web as an open-source project. This implementation of ASTEF got rid of many functionalities included in the previous version that are not needed anymore considering the large availability of commercial and open-source software solutions for eye-tracking. That makes it very easy to compute the NNI on eye-tracking data without the hassle of learning complicated tools. The software also features an export function for creating the time series of the NNI values computed on each minute of the recording. This feature is crucial given that the spatial distribution of fixations must be used to test hypotheses about the time course of mental load.

Comparing Different Measures of Overall Workload in a Multimodal Postural/Auditory Dual-Task Environment

OCCUPATIONAL APPLICATIONS This study investigated the effects of a multimodal dual-task paradigm (balance and cognitive tasks) on overall mental workload. The balance task did not affect the performance of the cognitive task, and the presence of the cognitive task led to better balance performance with unstable seating. Simultaneously, measures of overall mental workload showed a general increase when the cognitive task was added and, in some cases, when the balancing task became harder (more unstable). These results generate two important implications. First, the performance levels of two multimodal tasks being done concurrently are insufficient to explain the overall workload in the system. Even if performance is not negatively (or even positively) affected initially, workload increases and may approach or reach overload. Second, any single measure of performance or workload taken in situ might very well be insufficient to explain effectively the way an individual is interacting with their multitasking environment.TECHNICAL ABSTRACT Background: Audition and balance are important aspects of many multitasking environments; auditory signals are used for myriad different alerts and alarms, and balance is pivotal in the realms of factory and construction to avoid falling and risking injury or death. Furthermore, the demands of multiple tasks at once can interact, creating complex environments for which measures of overall workload would be beneficial. Purpose: The goal of this research was to quantify the effects of a cognitive/postural dual-task environment on overall workload. Methods: We utilized a dual-task protocol pairing an auditory discrimination task with a seated balancing task. We then measured performance on both tasks and overall workload using subjective (NASA Task Load Index) and physiological (heart rate variability) measures. Results: Cognitive task performance did not change across different balance conditions, while the presence of the cognitive task decreased postural sway when the participants were unstable. The results regarding workload measures were varied; however, most indicated an increase in workload with the cognitive task. Conclusions: These two results might seem contradictory, with performance in the postural task increasing as the overall workload increases. Taken together, though, they suggest two important conclusions: the need to use more than one method of workload measurement and the importance of understanding the arousal level created by the environment and task difficulty. Designs of auditory alerts in situations involving physical demands should consider arousal levels and possible overload and avoid overvaluing single metrics.

Fighter pilots’ heart rate, heart rate variation and performance during instrument approaches

Fighter pilots’ heart rate (HR), heart rate variation (HRV) and performance during instrument approaches were examined. The subjects were required to fly instrument approaches in a high-fidelity simulator under various levels of task demand. The task demand was manipulated by increasing the load on the subjects by reducing the range at which they commenced the approach. HR and the time domain components of HRV were used as measures of pilot mental workload (PMWL). The findings of this study indicate that HR and HRV are sensitive to varying task demands. HR and HRV were able to distinguish the level of PMWL after which the subjects were no longer able to cope with the increasing task demands and their instrument landing system performance fell to a sub-standard level. The major finding was the HR/HRV’s ability to differentiate the sub-standard performance approaches from the high-performance approaches.Practitioner Summary:This paper examined if HR and HRV were sensitive to varying task demands in a fighter aviation environment and if these measures were related to variations in pilot’s performance.

Average heart rate for driver monitoring systems

With semi-autonomous vehicles being pushed onto the market, driver monitoring systems play a relevant role in determining the user's level of engagement whenever an automated-to-manual transition of control is scheduled to occur. As current monitoring systems heavily rely on steering behaviour and ocular parameters as inputs for their algorithms, this study aims to investigate whether average heart rate represents a sensitive measure of driver mental workload. Participants from three different age groups (21-34, 35-53, 54-70 years old) were considered and the combined effects of mental workload (induced by interacting with the in-vehicle infotainment system via voice) and aging on average heart rate were investigated. Average heart rate was recorded using a portable heart rate monitor for commercial use. Results showed that average heart rate increased as the secondary task became more demanding. Furthermore, a significant task × age interaction suggested that as the secondary task became more demanding, younger drivers showed an increased heart rate compared to older drivers. These results are of the primary importance for the design of adaptive workload monitoring systems.

Average heart rate for driver monitoring systems

With semi-autonomous vehicles being pushed onto the market, driver monitoring systems play a relevant role in determining the user's level of engagement whenever an automated-to-manual transition of control is scheduled to occur. As current monitoring systems heavily rely on steering behaviour and ocular parameters as inputs for their algorithms, this study aims to investigate whether average heart rate represents a sensitive measure of driver mental workload. Participants from three different age groups (21-34, 35-53, 54-70 years old) were considered and the combined effects of mental workload (induced by interacting with the in-vehicle infotainment system via voice) and aging on average heart rate were investigated. Average heart rate was recorded using a portable heart rate monitor for commercial use. Results showed that average heart rate increased as the secondary task became more demanding. Furthermore, a significant task × age interaction suggested that as the secondary task became more demanding, younger drivers showed an increased heart rate compared to older drivers. These results are of the primary importance for the design of adaptive workload monitoring systems.

Exploring the Relationship between Mental Workload, Variation in Performance and Physiological Parameters

Abstract: Real time non-intrusive mental workload level estimation may lead to significant improvements in the design and operation of future flight decks, reducing the cognitive demand on pilots. This study explores the relationship between mental workload, variation of performance and objective physiological measures. The study presented was performed in laboratory conditions and required participants to perform a custom-designed tracking task with elements of mental arithmetic that imposed varying levels of mental workload. The data collected consisted of: physiological measurements (heart inter-beat intervals, breathing rate, facial thermography); subjective ratings of workload from the participants (ISA and NASA-TLX); and the performance measured within the task. Initial results suggest facial thermography as a good candidate for non-intrusive mental workload measurements as temperature variations on some areas, for example the nose, appear to relate well to the changes in mental workload level as measured by subjective ratings as well as performance measures on performing the task.

Assessment of mental workload: A new electrophysiological method based on intra-block averaging of ERP amplitudes

The present study contributes to the current debate about electrophysiological measurements of mental workload. Specifically, the allocation of attentional resources during different complexity levels of tasks and its changes over time are of great interest. Therefore, we investigated mental workload using tasks varying in difficulty during an auditory oddball target paradigm. For data analysis, we applied a novel method to compute event-related potentials (ERPs) by intra-block epoch averaging of P2, P3a and P3b amplitude components for the infrequent target stimuli. We obtained eight consecutive blocks of 5 epochs each, which allowed us to develop an electrophysiological parameter to measure mental workload. In both the easy and the more constraining tasks, the amplitude of P2 decreased beginning with the second block of the sequence. In contrast, the amplitudes of P3a and P3b components linearly decreased following the repetition of the target in the more constraining task, but not in the easy task. Statistical analysis revealed intra-block differences on amplitudes of ERPs of interest between the easy and the more constraining tasks, confirming this method as a measure to assess mental workload. Since a subject is his own control, the present method represents an electrophysiological parameter for individual measurement of mental workload and may therefore be applicable in clinical routine.

Heart rate variability and cognitive processing: The autonomic response to task demands

This study investigated variations in heart rate variability (HRV) as a function of cognitive demands. Participants completed an execution condition including the psychomotor vigilance task, a working memory task and a duration discrimination task. The control condition consisted of oddball versions (participants had to detect the rare event) of the tasks from the execution condition, designed to control for the effect of the task parameters (stimulus duration and stimulus rate) on HRV. The NASA-TLX questionnaire was used as a subjective measure of cognitive workload across tasks and conditions. Three major findings emerged from this study. First, HRV varied as a function of task demands (with the lowest values in the working memory task). Second, and crucially, we found similar HRV values when comparing each of the tasks with its oddball control equivalent, and a significant decrement in HRV as a function of time-on-task. Finally, the NASA-TLX results showed larger cognitive workload in the execution condition than in the oddball control condition, and scores variations as a function of task. Taken together, our results suggest that HRV is highly sensitive to overall demands of sustained attention over and above the influence of other cognitive processes suggested by previous literature. In addition, our study highlights a potential dissociation between objective and subjective measures of mental workload, with important implications in applied settings.

Towards an effective cross-task mental workload recognition model using electroencephalography based on feature selection and support vector machine regression

Electroencephalographic (EEG) has been believed to be a potential psychophysiological measure of mental workload. There however remain a number of challenges in building a generalized mental workload recognition model, one of which includes the inability of an EEG-based workload classifier trained on a specific task to handle other tasks. The primary goal of the present study was to examine the possibility of addressing this challenge using feature selection and regression model. Support vector machine classifier and regression models were examined under within-task conditions (trained and tested on the same task) and cross-task conditions (trained on one task and tested on another task) for well-trained verbal and spatial n-back tasks. A specifically designed cross-task recursive feature elimination (RFE) based feature selection was used to handle the possible causes responsible for the deterioration of the performance of cross-task regression model. The within-task classification and regression performed fairly well. Cross-task classification and regression performance, however, deteriorated to unacceptable levels (around chance level). Trained and tested with the most robust feature subset selected by cross-task RFE, the performance of cross-task regression was significantly improved, and there were no significant changes in the performance of within-task regression. It can be inferred that workload-related features can be picked out from those which have been contaminated using RFE, and regression models rather than classifiers may be a wiser choice for cross-task conditions. These encouraging results suggest that the cross-task workload recognition model built in this study is much more generalizable across task when compared to the model built in traditional way.

Measurement of Mental Workload Changes during Laparoscopy with a Visual-Spatial Task

A visual-spatial secondary task was used as a measure of mental workload during the performance of a simulated laparoscopic surgical task. Task demands were manipulated by an increase in the degree of camera angle. NASA-TLX scores were used to corroborate changes in task demands. Results indicated that performance on the visual-spatial secondary task decreased with the increase in task demands associated with the increase in camera angle. NASA-TLX scores were consistent with the performance measures revealing that participants felt the laparoscopic task was more demanding when camera angle increased. The use of similar workload assessment methods may allow for more accurate estimates of the mental demands imposed by laparoscopy. These results show that the spatial secondary task used in this study can provide an objective index of mental workload that can complement traditional measures.

Considerations For Using Subjective Mental Workload Measures In Populations With Cognitive Deficits

Mental workload measurement has been a traditional and well-used method in human factors for over 50 years and continues to be highly relevant today. It has been applied to a variety of fields, including healthcare, though subjects have been clinicians rather than patients. Subjective mental workload measures are based on the assumptions that subjects can report self-functioning (i.e. persons with complete cognitive functioning). Thus, if subjective mental workload is applied to a population of persons with limited and / or dynamically changing cognitive functioning, then the basic assumptions of subjective mental workload are violated. This paper explores the considerations for incorporating subjective mental workload measurement tools into rehabilitative practices for cognitive deficits, such as traumatic brain injury and stroke patients.

EFFECTIVE INDICES FOR MONITORING MENTAL WORKLOAD WHILE PERFORMING MULTIPLE TASKS.

This study identified several physiological indices that can accurately monitor mental workload while participants performed multiple tasks with the strategy of maintaining stable performance and maximizing accuracy. Thirty male participants completed three 10-min. simulated multitasks: MATB (Multi-Attribute Task Battery) with three workload levels. Twenty-five commonly used mental workload measures were collected, including heart rate, 12 HRV (heart rate variability), 10 EEG (electroencephalography) indices (α, β, θ, α/θ, θ/β from O1-O2 and F4-C4), and two subjective measures. Analyses of index sensitivity showed that two EEG indices, θ and α/θ (F4-C4), one time-domain HRV-SDNN (standard deviation of inter-beat intervals), and four frequency-domain HRV: VLF (very low frequency), LF (low frequency), %HF (percentage of high frequency), and LF/HF were sensitive to differentiate high workload. EEG α/θ (F4-C4) and LF/HF were most effective for monitoring high mental workload. LF/HF showed the highest correlations with other physiological indices. EEG α/θ (F4-C4) showed strong correlations with subjective measures across different mental workload levels. Operation strategy would affect the sensitivity of EEG α (F4-C4) and HF.

Avionic technology testing by using a cognitive neurometric index: A study with professional helicopter pilots.

In this study, we investigated the possibility to evaluate the impact of different avionic technologies on the mental workload of helicopter's pilots by measuring their brain activity with the EEG during a series of simulated missions carried out at AgustaWestland facilities in Yeovil (UK). The tested avionic technologies were: i) Head-Up Display (HUD); ii) Head-Mounted Display (HMD); iii) Full Conformal symbology (FC); iv) Flight Guidance (FG) symbology; v) Synthetic Vision System (SVS); and vi) Radar Obstacles (RO) detection system. It has been already demonstrated that in cognitive tasks, when the cerebral workload increases the EEG power spectral density (PSD) in theta band over frontal areas increases, and the EEG PSD in alpha band decreases over parietal areas. A mental workload index (MWL) has been here defined as the ratio between the frontal theta and parietal alpha EEG PSD values. Such index has been used for testing and comparing the different avionic technologies. Results suggested that the HUD provided a significant (p<;.05) workload reduction across all the flight scenarios with respect to the other technologies. In addition, the simultaneous use of FC and FG technologies (FC+FG) produced a significant decrement of the workload (p<;.01) with respect to the use of only the FC. Moreover, the use of the SVS technology provided on Head Down Display (HDD) with the simultaneous use of FC+FG and the RO seemed to produce a lower cerebral workload when compared with the use of only the FC. Interestingly, the workload estimation by means of subjective measures, provided by pilots through a NASA-TLX questionnaire, did not provide any significant differences among the different flight scenarios. These results suggested that the proposed MWL cognitive neurometrics could be used as a reliable measure of the user's mental workload, being a valid indicator for the comparison and the test of different avionic technologies.

The Quantification of Surgeon Opinion

Subjective operator evaluation remains a key method of assessing the interactions between operator-device performance and total workload. Rating scales serve as a valuable method for measures of physical and mental workload in other industries. To address this need, we looked for inspiration in the aviation community where requirements for flight tests have resulted in the development of tools to quantify pilot opinion. The rating scale maps subjective ratings to specific design criteria and will help engineers understand where in the device design problems are occurring.

P300 event-related potential as an indicator of inattentional deafness?

An analysis of airplane accidents reveals that pilots sometimes purely fail to react to critical auditory alerts. This inability of an auditory stimulus to reach consciousness has been coined under the term of inattentional deafness. Recent data from literature tends to show that tasks involving high cognitive load consume most of the attentional capacities, leaving little or none remaining for processing any unexpected information. In addition, there is a growing body of evidence for a shared attentional capacity between vision and hearing. In this context, the abundant information in modern cockpits is likely to produce inattentional deafness. We investigated this hypothesis by combining electroencephalographic (EEG) measurements with an ecological aviation task performed under contextual variation of the cognitive load (high or low), including an alarm detection task. Two different audio tones were played: standard tones and deviant tones. Participants were instructed to ignore standard tones and to report deviant tones using a response pad. More than 31% of the deviant tones were not detected in the high load condition. Analysis of the EEG measurements showed a drastic diminution of the auditory P300 amplitude concomitant with this behavioral effect, whereas the N100 component was not affected. We suggest that these behavioral and electrophysiological results provide new insights on explaining the trend of pilots’ failure to react to critical auditory information. Relevant applications concern prevention of alarms omission, mental workload measurements and enhanced warning designs.

Frequency of Application of Mental Workload Measuring Instruments in Recent Publications in Brazil

Mental workload is crucial factor when analysing cognitive and physical aspects of the job. Thus, instruments that allow the measurement of mental workload become possible a better ergonomic work analysis. This research aims to identify the use of instruments to measure mental workload in articles recently published in Brazilian journals. It's an article of literature review, focusing the national production of articles in the last five years that deal with mental workload and its measurement. Research carried out at CAPES portal of periodic, using as search term mental workload, stating in the subject. Were considered only articles of the past 5 years, published in national journals, which have had some type of mental workload scale, by analysing the abstracts. Twenty-five references were found, only two of these articles using NASA-TLX as a tool for measuring mental workload. There‘s a predominance of use of instruments that detect mental distress (e.g., the diagnosis of burnout); instruments that assess quality of life, or the scale of psychosocial risk factors at work. Thus, it comes to diagnoses work-related psychopathology or sizing risk of illness at work. The production of knowledge tends to focus on the consequences generated by an inefficient practice or organization of work. However, the practice of ergonomic analysis of work comprising the measurement of mental workload is rarely seen in recent national publications.