Cardiovascular and eye activity measures as indices for momentary changes in mental effort during simulated flight

This study examines effects of momentary changes in mental effort on cardiovascular and eye activity measures. A total of 19 male pilots performed an instrument flight task. Task load was manipulated by having the pilots perform flight manoeuvres of varying complexity. Multilevel analyses demonstrated clear effects of momentary changes in mental effort on both the cardiovascular and the eye activity measures. An increase in task load resulted in an increase of heart rate and a decrease in heart rate variability, mean dwell time and fixation duration. Heart rate differentiated between resting period and task execution. Heart rate variability from short data segments provided more insight in intermediate levels of mental effort. The eye activity measures were sensitive to intermediate levels of mental effort as well. Attitude changes resulted in an increase of mean dwell time and mean fixation duration. Task analysis is required to use eye measures as valid indices of mental effort. Having indications of the effects of changing mental demands during daily work of operators is of great importance nowadays. This paper presents an approach to estimate such effects on the basis of heart rate and eye activity measures. In particular, the use of averaged short-term heart rate variability measures is a relatively new aspect.     

Combining electrodermal responses and cardiovascular measures for probing adaptive automation during simulated flight

Adaptive automation increases the operator's workload in case of hypovigilance and takes over more responsibility if workload becomes too high. Two consecutive studies were conducted to construct a biocybernetic adaptive system for a professional flight simulator, based on autonomic measures. Workload was varied through different stages of turbulences. In a first study with 18 participants, electrodermal responses of experimental subjects oscillated very close to the individual set point, demonstrating that workload level was adjusted as a result of adaptive control, which was not the case in yoked control subjects without adaptive automation. Combining electrodermal responses with heart rate variability in a second study with 48 participants further enhanced the adaptive power which was seen in even smaller set point deviations for the experimental compared to the yoked control group. We conclude that the level of arousal can be adjusted to avoid hypovigilance by combining autonomic measures in a closed loop.     

Comparison of NASA-TLX scale,modified Cooper–Harper scale and mean inter-beat interval as measures of pilot mental workload during simulated flight tasks

Abstract

The sensitivity of NASA-TLX scale, modified Cooper–Harper (MCH) scale and the mean inter-beat interval (IBI) of successive heart beats, as measures of pilot mental workload (MWL), were evaluated in a flight training device (FTD). Operational F/A-18C pilots flew instrument approaches with varying task loads. Pilots’ performance, subjective MWL ratings and IBI were measured. Based on the pilots’ performance, three performance categories were formed; high-, medium- and low-performance. Values of the subjective rating scales and IBI were compared between categories. It was found that all measures were able to differentiate most task conditions and there was a strong, positive correlation between NASA-TLX and MCH scale. An explicit link between IBI, NASA-TLX, MCH and performance was demonstrated. While NASA-TLX, MCH and IBI have all been previously used to measure MWL, this study is the first one to investigate their association in a modern FTD, using a realistic flying mission and operational pilots.

Practitioner summary: NASA-TLX scale, MCH scale and the IBI were evaluated in a flight training device. All measures were able to differentiate most task conditions and there was a positive correlation between NASA-TLX and MCH scale. An explicit link between IBI, NASA-TLX, MCH and performance was demonstrated.

Abbreviations: ANOVA: Analysis of Variance; ECG: Electrocardiograph; F/A: fighter/attack; ft: feet; FTD: flight training device; G: Gravity; km: kilometer; m: meter; m/s: meters per second; MWL: mental workload; MCH: modified cooper-harper; NASA-TLX: NASA Task Load Index; NM: Nautical Mile; NN: normal-to-normal; IBI: inter-beat interval; ILS: Instrument Landing System; RR: R-Wave to R-Wave; SD: standard deviation; TTP: tactics, techniques and procedures; WTSAT: Weapon Tactics and Situation Awareness Trainer     

Cardiovascular state changes during performance of a simulated ambulance dispatchers' task: Potential use for adaptive support

Adaptive support has the potential to keep the operator optimally motivated, involved, and able to perform a task. In order to use such support, the operator's state has to be determined from physiological parameters and task performance measures. In an environment where the task of an ambulance dispatcher was simulated, two studies have been carried out to evaluate the feasibility of using cardiovascular measures for adaptive support. During performance of this 2–3 h lasting planning task, a pattern of results is found that can be characterized by an initial increase of blood pressure and heart rate and a decrease of heart rate variability (defense reaction pattern) followed by an ongoing increase of blood pressure counteracted by a decrease in heart rate. This pattern can be explained by an augmented short-term blood pressure control (baroreflex), which is reflected in an increase of baroreflex sensitivity. Additionally, in this latter phase heart rate variability (HRV) increases as a function of time, while blood pressure variability decreases. In the two studies performed, the baroreflex pattern was consistent for all the relevant variables.In both studies there were periods with high and low workload. Effects of task load are mainly reflected in the variability measures, while in the second study, additionally, blood pressure level was higher during periods with high task demands.The conclusion of the studies is that consistent cardiovascular response patterns can be recognized during this semi-realistic planning task, where variability measures are most sensitive to task demand changes, while blood pressure and baroreflex sensitivity are most informative with respect to cardiovascular state changes. These findings can be seen as a great potential benefit for future use in adaptive support applications.     

Using consumer-grade wearables and novel measures of sleep and activity to analyze changes in behavioral health during an 8-month simulated Mars mission

For analyzing changes in an individual's health over time, this research has developed objective measures for comparing behavioral patterns, including sleep quality and activity scores. These novel measures of behavioral health have provided insight about how sleep debt accumulates after long, extended days, how sleep disruption and recovery from wakefulness occur during the night, and when cross-correlations exist between measures. This data-driven approach to quantifying behavioral patterns is informed by minute-by-minute data from consumer-grade, wrist-worn wearables. In this 8-month longitudinal study, Jawbone UP wristbands and the Jawbone UP API were utilized to collect minute-by-minute data about the behavior of crewmembers participating in a simulated Mars mission. To study the challenges of living and working on the planet Mars, for eight months, these crewmembers were confined to a Mars-like habitat, living in close quarters, isolated from the rest of humanity at a high elevation on Mauna Loa volcano in Hawaii, wearing mock spacesuits while exploring the volcanic terrain, consuming shelf-stable foods, restricted in water usage, relying on solar energy, and delayed in communications with 20-min lag-times for delivering messages to and from the crew. Analyzing the behavior of these astronaut-like individuals has led to the development of objective measures for quantifying sleep patterns, that have potential for contributing to the development of next-generation, smart wearables.     

Heart period variability as mental effort monitor in Human Computer Interaction

Elementary steps of H uman Computer Interaction (HCI), like users' mental actions followed by a series of keystrokes and mouse-clicks, are the basic components of using information technological systems. This is why examination methods capable of assessing users' actual mental effort corresponding to these elementary steps during HCI in a scientifically sound way have great importance. It is known that under certain circumstances, Heart Period Variability (HPV) could be a measure of actual mental effort. This paper gives a short overview of applications of HPV in ergonomics in general and, based on empirical evidence intends to prove that this methodology, after a careful adaptation, could be powerful technique for monitoring mental effort in HCI. The paper outlines the main components of the INTERFACE testing workstation and the related methodology for investigatingamong others-users mental effort. A detailed application example is also provided.     

Heart period variability as mental effort monitor in Human Computer Interaction

Elementary steps of H uman Computer Interaction (HCI), like users' mental actions followed by a series of keystrokes and mouse-clicks, are the basic components of using information technological systems. This is why examination methods capable of assessing users' actual mental effort corresponding to these elementary steps during HCI in a scientifically sound way have great importance. It is known that under certain circumstances, Heart Period Variability (HPV) could be a measure of actual mental effort. This paper gives a short overview of applications of HPV in ergonomics in general and, based on empirical evidence intends to prove that this methodology, after a careful adaptation, could be powerful technique for monitoring mental effort in HCI. The paper outlines the main components of the INTERFACE testing workstation and the related methodology for investigatingamong others-users mental effort. A detailed application example is also provided.     

Pilots’ gaze strategies and manual control performance using occlusion as a measurement technique during a simulated manual flight task

The aim of this study was to analyze pilots’ visual scanning under conditions visually restricted by the occlusion paradigm. During manual flight, pilots experienced interruptions in their panel scan due to concurring tasks and monitoring of distant displays. Eleven volunteer airline pilots performed several manual instrument landing system approaches in a fixed-base flight simulator. Some of these approaches were performed using the paradigm of occlusion with shutter glasses. Under occlusion, the gaze pattern analysis revealed that pilots demonstrated reduced mean glance durations, but did not reduce their attention to lesser information displays. The results also indicated that the attitude indicator (artificial horizon) as a preview instrument was less affected by occlusion compared to other areas of interest. A subsequent scanpath analysis revealed that vertical tracking was the predominant information acquisition strategy and corresponded to larger deviations on the glideslope. These results imply the need to optimize information even for short glances, and to be very cautious with adaptive layouts of free programmable or dynamic displays, and not to overburden the pilot flying with parallel tasks.     

Peripheral arterial tone as an on-line measure of load in a simulated flight task

Variations in continuous and discrete flight demands were investigated in a simulated flight mission measuring peripheral arterial tone (PAT) from the tip of the finger. A total of 12 participants performed a computer-simulated agricultural flight task. They were required to fly over a specific lane of a simulated corn field (continuous task) and change lanes in response to flags, which appeared at varying intervals (discrete task). The difficulty of the flight task was manipulated by varying the airplane control (single- vs. dual-axis control), while the difficulty of the discrete task was manipulated by varying the amount of lateral change signalled by the flag. PAT amplitude was lower in the difficult level of the continuous task and was further attenuated following the appearance of the flag only when a change in the flight position was required. These results suggest the potential utility of PAT as an on-line measure of the joint continuous and discrete demands of a flight mission.     

Peripheral arterial tone as an on-line measure of load in a simulated flight task

Variations in continuous and discrete flight demands were investigated in a simulated flight mission measuring peripheral arterial tone (PAT) from the tip of the finger. A total of 12 participants performed a computer-simulated agricultural flight task. They were required to fly over a specific lane of a simulated corn field (continuous task) and change lanes in response to flags, which appeared at varying intervals (discrete task). The difficulty of the flight task was manipulated by varying the airplane control (single- vs. dual-axis control), while the difficulty of the discrete task was manipulated by varying the amount of lateral change signalled by the flag. PAT amplitude was lower in the difficult level of the continuous task and was further attenuated following the appearance of the flag only when a change in the flight position was required. These results suggest the potential utility of PAT as an on-line measure of the joint continuous and discrete demands of a flight mission.     

Cardiac measures of driver workload during simulated driving with and without visual occlusion

Cardiac (heart rate, pre-ejection period, and respiratory sinus arrhythmia), performance, and visual demand measures of driver workload were obtained from 15 male university students who drove a simulated course multiple times at a fixed speed of 72.4 km/h. The course contained curves of 3 different radii (582, 291, and 194 m) and was driven with and without visual occlusion of the road scene to manipulate driver workload. Visual occlusion of the road scene significantly reduced driving performance but did not affect the cardiac measures. Driving performance significantly deteriorated and visual demand significantly increased as curve radius decreased. The cardiac measures were differentially affected by curve radius, indicating different modes of autonomic control for the 291-m curve as compared with the 582- and 194-m curves. The patterns of dissociation across the cardiac, performance, and visual demand measures were interpreted as being capable of isolating the perceptual demands of driving from the central and motor processing demands. A potential application of this research is that the combination of psychophysiological and visual occlusion methodologies are a powerful research tool to assess performance and processing resource cost trade-offs associated with using advanced in-vehicle technologies.     

Eye movement and pupillary response indices of mental workload during visual search of symbolic displays

Eye movement and pupillary response measures (in addition to search time and accuracy) were collected as indices of visual workload during two experiments designed to evaluate the addition of colour coding to a symbolic tactical display. Displays also varied with regard to symbol density and the type of information participants were required to abstract from the display. These variables were factorially manipulated to examine the effects of colour coding in conditions of varying difficulty. In Experiment 1 (n = 8), search time and the number of eye fixations were affected by all variables and in a similar manner; fixation dwell time and the pupillary response dissociated from the other measures. Compared to monochrome displays, colour coding facilitated search (reduced search time, but not accuracy) during exhaustive search, but had no effect during self-terminating search. Experiment 2 (n = 8) was a replication of Experiment 1 with a pseudo-search control condition added to examine further the pupillary response measures: in particular, to assess the effects of the physical parameters of the displays, and to verify the findings of Experiment 1. Pupillary response measures were sensitive to the information processing demands of the search task, not merely to the physical parameters of the display. Further, the search time, accuracy, and eye movement results from the active search condition generally replicated Experiment 1, but the fixation dwell time data did not. These between-study differences were interpreted as indicating the importance of participant search strategy.     

Hyperspectral indices for detecting changes in canopy reflectance as a result of underground natural gas leakage

Natural gas leakage from underground pipelines is known to affect vegetation adversely, probably by displacement of the soil oxygen needed for respiration. This causes changes in plant and canopy reflectance, which may serve as indicators of gas leakage. In this study, a covariance analysis was performed between reflectance indices of maize (Zea mays) and wheat (Triticum aestivum) canopies and oxygen concentrations in a simulated natural gas leak. Twenty‐nine days after oxygen shortage occurred, the reflectance indices had the highest correlation with oxygen concentrations in the soil, for both species. The effect was consistent within species but the absolute values varied between the species. Normalization by adding a constant value to the control index of one species resulted in significant linear regression models for several indices. The indices with the highest regression coefficients were used to predict the oxygen concentration in the soil. This showed that the gas leakage caused reflectance changes up to 0.5 m from the source. As it could not be proven that oxygen shortage was the cause of the reflectance changes, further work is needed to study the side‐effects of gas leakage, such as bacterial oxygen depletion, on plant growth and reflectance.     

Passive stiffness changes in the lumbar spine and effect of gender during prolonged simulated driving

Gender differences in lumbar and pelvic posture have been reported previously in prolonged sitting, both in an office chair and automobile seat. To date, it is not known whether these postural exposures during prolonged driving affect the passive lumbar spine flexion stiffness. The purpose of this study was to examine time-varying responses of passive lumbar spine stiffness, lumbar spine and pelvic postures during a 2 h simulated driving trial. Secondary goals investigated the influence of gender on lumbar spine stiffness, discomfort scores and seat pressure profiles. Twenty (10 males, 10 females) subjects were recruited to complete a 2 h simulated driving task. Passive lumbar range of motion was measured on a customized frictionless jig before, halfway through and at the end of 2 h. During driving there was a time-varying difference in the lumbar flexion angles adopted by the gender groups. A significant interaction (p = 0.0458) was found for gender and time with women being found to sit significantly different than males in the second hour of driving exhibiting greater maximum lumbar flexion (60.0% ROM (±1.27) than men 50.0% ROM (±1.5). Both men and women demonstrated similar passive stiffness changes characterized by an initial increase in transitional zone stiffness after 1 h (+0.1 Nm/degree for males and +0.3 Nm/degree for females, p = 0.2372). Over 2 h of driving there was a non-significant trend of genders to respond differently to the seated exposure. Specifically transitional zone stiffness was found to increase in males (0.86 (SD 0.31) to 0.92 (SD 0.31) Nm/degree) and decrease in females (0.81 (SD0.88) to 0.73 (SD 0.52) Nm/degree) (p = 0.1178). Differences in lumbar posture and passive stiffness over 2 h of simulated driving were demonstrated between genders in this study.Relevance to industryGender specific ergonomic interventions should be investigated for the automobile seat. Additionally, the changes in passive stiffness induced by prolonged seated exposures could introduce altered low back kinematics in activities performed after a long car ride. Lifting scenarios such as luggage unloading or parcel delivery are common activities immediately after driving. The altered stiffness of the lumbar spine in these activities could have potential ergonomics and injury related implications for both the general population and professional drivers.     

Electronic outlining as a writing strategy: Effects on students' writing products,mental effort and writing process

This study addresses to what extent and how electronic outlining enhances students' writing performance. To this end, the focus of this study is not only on students' final writing products but also on the organisation of the writing process (i.e., planning, translating, and reviewing) and perceived mental effort during writing. In addition, effects of repeated electronic outlining were examined. A combined within and between subjects design was implemented in which 93 10th-grade students wrote two argumentative texts with or without using electronic outlining. Analyses showed that using electronic outlining for planning and writing significantly improved the presentation of the argumentative structure. However, effects were less clear for correctly and completely establishing a text structure and no effects were found on the elaboration of students' argumentation. Process data showed that electronic outlining increased total process time, but no effect was found on students' overall planning and revision activities. Finally, self-reports showed no effect of electronic outlining on students' perceived mental effort. Nevertheless, repeated use of the same writing strategy enhanced writing fluency.     

Effectiveness of rest pauses and cooling in alleviation of heat stress during simulated fire-fighting activity

This study examined whether cooling a fire-fighter with a high velocity fan, during 10 min rest pauses between, and following, 10 min work periods, decreases heat stress during repetitive fire-fighting activity. Twelve professional fire-fighters (mean age 31.8 +/- 6.7 years) completed two, 40 min work/recovery trials in an environmental chamber at 40 degrees C and 70% relative humidity (RH). One trial was termed an enhanced recovery (ER) trial and the other was termed a normal recovery (NR) trial. In both conditions subjects wore full protective clothing and breathing apparatus during the work. In the ER trial a subject removed his protective coat and sat in front of a fan during each recovery period. In the NR trial a subject merely unbuckled his coat and was not cooled by a fan during either recovery period. The group mean metabolic cost (VO2), and the exercise and recovery heart rates were significantly lower (p < or = 0.05) during the ER trial than in the NR condition. Group mean rectal temperature increased by 1.5 degrees C in the NR trial but by only 0.8 degree C during the ER trial. The latter group's more effective cooling indicates the potential of fan cooling to reduce physiological strain and decrease the risk of heat exhaustion during repetitive fire-fighting activity. The results suggest that a fire-fighter's short 10 min exposure to heavy work in a hot environment of 40 degrees C and 70% RH produces minimal heat stress in a healthy fire-fighter. However, a period of fire-fighting exposure greater than 10 min without adequate rest and cooling may lead to a significant accumulation of heat stress and fatigue during further fire-fighting activity, irrespective of physical prowess.     

Self-assessed changes in mental health and employment status as a result of unemployment training

The main question addressed in this article is: What factors in an unemployment programme serve both the individual and society? Our research focuses on background variables and process variables and how these can be assumed to affect certain dependent variables in unemployment training. The current focus is on the dependent variable "subjective assessment of the effect of the training on mental health", together with the more objective dependent variable of "employment status after training". Self-confidence, well-being, faith in the future, level of initiative and personal development have been used as indicators of self-assessed "mental health". Data were collected from an unemployment training programme in Sweden and the variables combined to create a hypothetical model. The model was statistically tested and then modified with the aid of LISREL statistics, which helps to adjust the model to statistical acceptance. The findings show that the salient factors directly related to the subjective assessment of the effect of training on mental health are gender, attitude to skills development, perceived training requirements and formal educational background. The latter relationship was negative. Of indirect importance are the level of commitment of the teacher, the satisfaction of the trainee with the process, and the level of control. The duration of previous unemployment was the only independent variable, which directly affected the employment status after the training, and this was in the negative direction. Of indirect importance for this dependent variable were training requirement, satisfaction with the process, own level of control and attitude to skills development.     

Dynamic problem selection in air traffic control training: a comparison between performance,mental effort and mental efficiency

The differential effects on training and training outcome of four methods of problem selection were investigated in a computer-based training for air traffic control. In one method, training problems were given to the participants in a fixed predetermined sequence, from simple to complex. In the other methods, problems were selected dynamically, based on three different learner variables. These were mental effort, performance and mental efficiency, which is a variable that combines mental effort and performance measures to determine problem efficiency. After the training, transfer was measured. The hypothesis that dynamic problem selection would lead to more efficient training than non-dynamic problem selection was confirmed. The second hypothesis, that dynamic problem selection based on mental efficiency would lead to more efficient training and better transfer than dynamic problem selection based on performance or mental effort alone was not supported. However, the efficiency measures of the three variables were distorted by the differential effects of these variables on the acquisition phase. A possible explanation for the results is that selection based on performance stimulates rule automation, whereas selection based on mental effort or mental efficiency leads to schema acquisition.