Effect of varying levels of mental workload on startle eyeblink modulation

Previous research using punctuate reaction time and counting tasks has found that the startle eyeblink reflex is sensitive to attentional demands. The present experiment explored whether startle eyeblink is also modulated during a complex continuous task and is sensitive to different levels of mental workload. Participants (N = 14) performed a visual horizontal tracking task either alone (single-task condition) or in combination with a visual gauge monitoring task (multiple-task condition) for three minutes. On some task trials, the startle eyeblink reflex was elicited by a noise burst. Results showed that startle eyeblink was attenuated during both tasks and that the attenuation was greater during the multiple-task condition than during the single-task condition. Subjective ratings, endogenous eyeblink rate, heart period, and heart period variability provided convergent validity of the workload manipulations. The findings suggest that the startle eyeblink is sensitive to the workload demands associated with a continuous visual task. The application of startle eyeblink modulation as a workload metric and the possibility that it may be diagnostic of workload demands in different stimulus modalities is discussed.     

Heart period variability and respiratory changes associated with physical and mental load: non-linear analysis

In the investigation of heart rate and heart rate variability, the discrimination between mental workload, physical activity and respiration is known to be methodologically difficult. At most, heart rate variability measures are more likely to be coarse-grained measures with variability confounded by heart rate. Moreover, the spectral analysis of heart rate variability shows broad-band frequency characteristics, pointing towards non-stationarity or non-linearity. From this it is suggested to focus on non-linear dynamic analyses that are variance-insensitive. The experimental section of the paper focuses on the estimation of two non-linear measures for both heartbeat dynamics and respiration, the correlation dimension indicating complexity and the Lyapunov exponents indicating predictability. The results indicate that the complexity of heart dynamics is related to the type of task and that the predictability of heart dynamics is related to the amount of load.     

The influence of aircraft proximity data on the subjective mental workload of controllers in the air traffic control task

This paper outlines an investigation of the impact of aircraft proximity and relationship data on the subjective mental workload of air traffic controllers. Aircraft relationships were categorized into one of 81 different categories, and these relationships were then used to predict subjective mental workload values (as reported by the participants). The results indicated that this methodology could predict subjective mental workload to an accuracy of 73%, with post-hoc analysis improving this prediction rate to 93%. These results are discussed with respect to their contribution to an understanding of the drivers of mental workload in Air Traffic Control.     

A complete task analysis to measure the workload associated with operating an agricultural sprayer equipped with a navigation device

The objective of this study was to perform a complete task analysis to measure the workload associated with operating an agricultural sprayer equipped with a navigation device. The task analysis included a written questionnaire and subsequent observation of sprayer operators. The questionnaire revealed that the lightbar was the most important source of guidance information (as opposed to relying on guidance information from external field cues). Observation consisted of recording eye-glance behaviour and heart rate variability while operators were spraying in a field setting. The eye-glance data suggest that external cues are more important than the lightbar for providing the necessary navigation information. Thus, the questionnaire and observation data contradict each other. Based on heart rate variability, operators who used a lightbar navigation device experienced more mental workload than operators who used an auto-steer navigation device.     

an annotated bibliography

The modern office worker potentially faces a wide range of problems which may affect his or her health. The sources of many of these problems originate in the rapid proliferation of micro-computers in most organizations over the past few years. The present bibliography aims to guide the reader selectively into the literature on the problems of office work which may adversely affect employees' health arising from. the technology used or the environment at work. The bibliography does not cover more generic problem areas which currently may be of interest, such as the problems of stress, except where these have been studied in relation to technology or environment. It covers the period 1980-1986, although earlier work is cited where this is seen as important. The literature covered is not exhaustive, but sufficient for the reader to appreciate the main issues. The selection and interpretation of material inevitably reflects the interest and idiosyncracies of the author, but it is hoped that this will not detract from its usefulness.     

Muscle activity and cardiovascular response during computer-mouse work with and without memory demands

Computer-mouse work is characterized by repetitive movements combined with mental demands. The present purpose was to study how the body responded to simulated Computer Aided Design (CAD) work without memory demand and when a high short-term memory demand was introduced. Nine female subjects repetitively performed a task which involved 15 s of elevation of the right index and middle fingers followed by 6 s of rest. Every second time the fingers rested, the left index finger was required to type a six-figure number, either ‘123456’ (without memory demand) or a random number shown half a minute before (with memory demand). After 7 min of performing the task without memory demand, the memory demand was introduced and continued for 1 h. Introduction of memory demand resulted in increased heart rate (77 ← 84 beats/min), blood pressure (systolic 129 ← 140 mmHg; diastolic 72 ← 79 mmHg) and forearm extensor muscle activity (wrist, 2.7 ← 4.5% EMGmax; finger, 5.6 ← 7.5% EMGmax) and finger flexor muscle activity (0.7 1.2% EMGmax) indicating increased co-contraction. Hereafter, muscle activity and cardiovascular response tended to decrease. Self-reported stress and rating of perceived exertion (RPE) for the right shoulder increased throughout the period. Two additional sub-studies were inlcuded, which focused on adaptation to the physical load, showing a decrease in muscle activity and arousal, and reintroduction of the memory load, showing a lower response as compared to the initial response. The practical consequences of the findings suggest that job content should have variable mental demands.     

Micromovements and discomfort associated with flight mission with helmet operation tasks with different levels of cognitive workload

When performing stationary tasks under elevated cognitive workload, individuals must perform continual muscle contractions to maintain stability of the body, resulting in fatigue of the postural muscles. When the muscles perform these contractions in a prolonged manner, the body potentially responds through small changes in body movements—micromovements that may lead to discomfort. The study purpose was to evaluate impact of cognitive load on micromovements. The micromovements were measured during three different cognitive workloads; low, medium, and high. The NASA-TLX score was used to evaluate the perceived mental workload and discomfort was assessed by visual analog scale. In total, 60 subjects (30 males and 30 females) were recruited and performed cognitive tasks that simulated flight operations such as changing the radio frequency based on air traffic control messages, balancing the fuel levels in simulated fuel tanks, and aiming a reticle in a designated moving target using the cyclic control. Cognitive load was defined by the frequency of events. Micromovements were defined by changes in the center of pressure (COP) of the seat pan and COP standard deviation. It was found that the high cognitive workloads had the highest NASA-TLX scores including mental demands, temporal demands, and effort. The neck area had the highest overall levels of discomfort followed by upper back. The highest standard deviation for COP shift and number of micromovements occurred for medium cognitive workloads. While there were some interesting trends, few trends reached a statistical significance due to high variability among subjects for the outcome variables.     

Preliminary observations on parameters of human location

Abstract

A preliminary experimental field investigation was conducted on seventeen normal male adults to study the important observable parameters of human locomotion and the interrelationship existing among them. New generalized terms such as specific speed (statures s^?1), specific energy consumption (kJ kg^?1 min^?1), percentage increase of peak heart rate and a non-dimensionalized term, relative step length, have been introduced. Superiority of cadence and specific speed over speed and specific energy consumption over energy consumption has been observed and a single linear relationship connecting specific speed and specific energy consumption up to a speed of 6·7 m s^?1 (24 km h^?1) has been seen. Stair climbing and Baithaki exercises have been included as two other rhythmic activities for the sake of comparison with locomotion. Use of cadence as a relatively more important observable gait parameter for walking or running activity as well as for other rhythmic activities has been suggested. These findings have potential for application in the field of work study and industrial engineering.     

Effects of different stress settings on cardiovascular parameters and their relationship to daily life blood pressure in normotensives,borderline hypertensives and hypertensives

The aim of this study was to compare a traditional stress setting, consisting of two mental arithmetic tasks and two Stroop test modifications, and a stress setting of varying task demand and decision latitude according to Karasek's job strain model, with respect to their feasibility to elicit differences in cardiovascular reactivity and recovery in 20 normotensives, 20 borderline hypertensives, and 20 non-medicated hypertensives, carefully selected by means of World Health Organization criteria. In addition, the relationship between laboratory and everyday blood pressure was investigated. All subjects were tested under both stress settings in counterbalanced order. Blood pressure was recorded both intermittently from the brachial artery (Riva-Rocci) and continuously from the finger (Finapres). Heart rate and electrodermal activity were continuously measured as well. Furthermore, daily life blood pressure recorded by means of 24 h ambulatory monitoring during a normal working day served as criterion for the re-classification of the blood pressure groups by means of discriminant analysis using physiological recordings from baseline, test phases and rest phases. The groups did not show significant differences in their reactivity to the various mental stressors including the Karasek-model oriented ones but marked differences in their behaviour occurred during the 10 min of recovery following each stress setting. Both systolic and diastolic blood pressure in hypertensives failed to recover during this period. The results also showed the superiority of the Finapres method with respect to reflecting the dynamics of physiological recovery processes. None of the stress settings showed an advantage in predicting blood pressure in daily life. In general, the results question the validity of mental laboratory stressors for the prediction of cardiovascular changes in daily life but point to a possible role of recovery processes after stress in the development of essential hypertension.