A comparison between the responsiveness of selected physiological and subjective mental workload indicators during real-world driving scenarios
- Authors: Schmidtke, Nadia-Jasmine
- Date: 2020
- Subjects: Automobile driving -- Physiological aspects , Automobile driving -- Psychological aspects , Automobile drivers -- Health and hygiene , Mental fatigue , Mental work -- Case studies
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/148115 , vital:38711
- Description: Sub-optimal levels of mental workload in automobile drivers is a risk factor for road accidents. However, mental workload as a construct cannot be directly measured. Common indicators of mental workload include heart rate frequency and variability, eye motion and subjective rating tools. Namely, the National Aeronautics and Space Administration Task Load Index (NASA-TLX), its modified, unweighted version called the Raw-TLX, and the Rating Scale of Mental Effort (RSME). Comparisons between the suitability and responsiveness of these mental workload indicators have been almost exclusively examined in driving simulators. However, real-world driving research is important as even high-fidelity simulators cannot capture the complexity of driving scenarios. Hence, this research aimed to compare the suitability and responsiveness of these mental workload indicators in response to real-world driving scenarios. Six participants drove along a set route for an hour while wearing a heart rate monitor and eye tracker. A dashcam was used to capture footage of the different driving scenarios encountered. The set route comprised of driving through the industrial, residential, provincial main road and Rhodes University campus areas. RSME scores were taken during brief stops after driving though each zone. The NASA-TLX questionnaire was administered on completion of the drive and analysed later as the modified Raw-TLX version. The data collected in response to the encountered driving scenarios were sorted into three meta-groupings. (1) Data was segmented according to the different areas that participants drove through. This was termed Area Events and were long duration scenarios of between five and thirty minutes. These driving scenarios were further segmented into two meta-groups with short duration driving scenarios (< 90 seconds). (2) The Common Events meta-group consisted of driving scenarios that were encountered by all participants. These were scenarios were anticipated by drivers. (3) The All Events meta-group was grouped according to all the driving scenarios that were encountered by participants. It consisted of both anticipated and unanticipated driving scenarios of short durations. Data were further analysed using a method of systematically selecting a threshold value for each mental workload indicator. Responses to driving scenarios which surpassed the threshold were considered indicative of an increase in mental workload. The total frequency of higher mental workload events was used as a determiner responsiveness (or ‘sensitivity’) for each mental workload indicator. Mental workload indicators were evaluated for their responsiveness and suitability for assessing mental workload. Results found blink frequency to be a responsive mental workload indicator for all categories of driving scenarios. Blink frequency and duration were the most responsive short duration mental workload indicators. Furthermore, the indicators were able to distinguish between higher and lower mental workload driving scenarios. However, blink parameters are also sensitive to driver fatigue and drowsiness. Further research on distinguishing mental workload from that of fatigue in response to real-world driving was recommended. Pupil diameter, fixation duration, saccade saccade duration and saccade amplitude were found to be responsive short duration mental workload indicators. However, these measures were not determined to be suitable for real-world driving applications. Pupil diameter was confounded by changing illumination levels. Fixation and saccade responses were confounded by the driving task itself as gaze could not be accounted for. For long duration driving scenarios heart rate frequency, heart rate variability: high-frequency power, blink frequency and RSME were found to be responsive and suitable MWL indicators. The Raw-TLX results could not be assessed for responsiveness as it was administered once. However, it was confirmed as a suitable cumulative mental workload indicator in the application of real-world driving. The moderate levels of workload reported by participants agreed with the experimental protocol that prevented inducing sub-optimal mental workload. Blink frequency shows promise as a responsive and suitable mental workload indicator for different types of driving scenarios. More research is needed regarding the assessment of mental workload during short durations using blink frequency and blink duration. For driving durations between five and thirty minutes long, further research into heart rate frequency, heart rate variability: high frequency power, and the RSME was recommended.
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- Authors: Schmidtke, Nadia-Jasmine
- Date: 2020
- Subjects: Automobile driving -- Physiological aspects , Automobile driving -- Psychological aspects , Automobile drivers -- Health and hygiene , Mental fatigue , Mental work -- Case studies
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/148115 , vital:38711
- Description: Sub-optimal levels of mental workload in automobile drivers is a risk factor for road accidents. However, mental workload as a construct cannot be directly measured. Common indicators of mental workload include heart rate frequency and variability, eye motion and subjective rating tools. Namely, the National Aeronautics and Space Administration Task Load Index (NASA-TLX), its modified, unweighted version called the Raw-TLX, and the Rating Scale of Mental Effort (RSME). Comparisons between the suitability and responsiveness of these mental workload indicators have been almost exclusively examined in driving simulators. However, real-world driving research is important as even high-fidelity simulators cannot capture the complexity of driving scenarios. Hence, this research aimed to compare the suitability and responsiveness of these mental workload indicators in response to real-world driving scenarios. Six participants drove along a set route for an hour while wearing a heart rate monitor and eye tracker. A dashcam was used to capture footage of the different driving scenarios encountered. The set route comprised of driving through the industrial, residential, provincial main road and Rhodes University campus areas. RSME scores were taken during brief stops after driving though each zone. The NASA-TLX questionnaire was administered on completion of the drive and analysed later as the modified Raw-TLX version. The data collected in response to the encountered driving scenarios were sorted into three meta-groupings. (1) Data was segmented according to the different areas that participants drove through. This was termed Area Events and were long duration scenarios of between five and thirty minutes. These driving scenarios were further segmented into two meta-groups with short duration driving scenarios (< 90 seconds). (2) The Common Events meta-group consisted of driving scenarios that were encountered by all participants. These were scenarios were anticipated by drivers. (3) The All Events meta-group was grouped according to all the driving scenarios that were encountered by participants. It consisted of both anticipated and unanticipated driving scenarios of short durations. Data were further analysed using a method of systematically selecting a threshold value for each mental workload indicator. Responses to driving scenarios which surpassed the threshold were considered indicative of an increase in mental workload. The total frequency of higher mental workload events was used as a determiner responsiveness (or ‘sensitivity’) for each mental workload indicator. Mental workload indicators were evaluated for their responsiveness and suitability for assessing mental workload. Results found blink frequency to be a responsive mental workload indicator for all categories of driving scenarios. Blink frequency and duration were the most responsive short duration mental workload indicators. Furthermore, the indicators were able to distinguish between higher and lower mental workload driving scenarios. However, blink parameters are also sensitive to driver fatigue and drowsiness. Further research on distinguishing mental workload from that of fatigue in response to real-world driving was recommended. Pupil diameter, fixation duration, saccade saccade duration and saccade amplitude were found to be responsive short duration mental workload indicators. However, these measures were not determined to be suitable for real-world driving applications. Pupil diameter was confounded by changing illumination levels. Fixation and saccade responses were confounded by the driving task itself as gaze could not be accounted for. For long duration driving scenarios heart rate frequency, heart rate variability: high-frequency power, blink frequency and RSME were found to be responsive and suitable MWL indicators. The Raw-TLX results could not be assessed for responsiveness as it was administered once. However, it was confirmed as a suitable cumulative mental workload indicator in the application of real-world driving. The moderate levels of workload reported by participants agreed with the experimental protocol that prevented inducing sub-optimal mental workload. Blink frequency shows promise as a responsive and suitable mental workload indicator for different types of driving scenarios. More research is needed regarding the assessment of mental workload during short durations using blink frequency and blink duration. For driving durations between five and thirty minutes long, further research into heart rate frequency, heart rate variability: high frequency power, and the RSME was recommended.
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An empirical investigation into task aversion
- Authors: Sunshine, Megan
- Date: 2013 , 2013-07-25
- Subjects: Work aversion , Mental fatigue , Labor productivity , Employees -- Workload , Industrial hygiene
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5138 , http://hdl.handle.net/10962/d1006085 , Work aversion , Mental fatigue , Labor productivity , Employees -- Workload , Industrial hygiene
- Description: Aversion is a complex phenomenon that arises over time through performance of cognitively demanding tasks and has been associated with the mechanisms of mental fatigue and compensatory control. However, little is known about this sensation to dissociate from the task at hand and the causation thereof. It is apparent that aversion is a negative state for the operator and could result in decreased performance and productivity. Through identification of factors that contribute to aversion when performing cognitively demanding tasks, recommendations to reduce design deficits may be employed to promote worker wellbeing and further advance performance and productivity. The current study examined possible factors that may influence aversion experienced through execution of cognitive tasks. A subsequent aim of this study was to assess a possible cause of aversion. The cause of aversion was hypothesized to be related to efficiency, namely the perception of efficiency when performing tasks and actual efficiency calculated through performance of tasks in relation to the expenditure of effort. Four investigations were undertaken with a non-repeated design between investigations and a repeated design within investigations. The first investigation was an analysis of the effect that stimulus cycling had on the aversion experienced. This consisted of a proof reading task with two conditions varying in the repetitiveness of the text, therefore, allowing an analysis as to how aversion is altered by the provision of a new stimulus to the participants. Investigation two investigated the effect that task difficulty imposed on aversion experienced. This comprised of two conditions with varied difficulty that were implemented through a driving simulator tracking task with difficulty altered by the width of the driving lane. The effect of performance feedback on the aversion experienced towards a task was the focus of the third investigation. The effect on aversion experienced was assessed through a driving simulator tracking task with a condition providing feedback of performance to participants and a condition with no knowledge of performance. The final experiment evaluated the effect of task alternations on aversion. This experiment was conducted through alternations between a driving simulator tracking task and a choice reaction task. The choice reaction tasks required participants to identify critical and non-critical stimulus. Four conditions were required for this experiment and were made up of two conditions where there was provision of alternation that varied in frequencies between the two tasks (medium alternation condition and fast alternation condition) and two conditions where no alternations were instated (driving simulator task condition and choice reaction task condition). Separations between all testing conditions were three or more days apart with sixty participants distributed between the investigations. Test duration of each condition was 30 minutes. Subjective data was recorded throughout investigations for all conditions in the form of aversion, subjectively perceived efficiency and rate of perceived exertion. Objective data was collected in the form of physiological responses and performance of tasks for the analysis of objective efficiency. For factors influencing aversion analysis, no differences in aversion experienced were found for the task difficulty and performance feedback investigations. Aversion was found to be less for the changes imposed through the task cycles and task alternation investigations. This concludes that aversion is aggravated through monotonous tasks and by a change of the stimulus or the structure of the cognitive tasks provided to operators; aversion can be alleviated. The results for the cause of aversion analysis found no difference in objective efficiency over time, with a subsequent decrease in perceived efficiency associated with the increasing aversion. Inference from these findings suggest that aversion cannot be attributed to objective inefficiency of task performance, however it can further be assumed that perception of actual efficiency is inaccurate. Perception of efficiency however had a large influence on the sensation of aversion. Aversion is seen to be more of a product of time on task, however whether this is mechanism of fatigue or compensatory control is still to be determined.
- Full Text:
- Authors: Sunshine, Megan
- Date: 2013 , 2013-07-25
- Subjects: Work aversion , Mental fatigue , Labor productivity , Employees -- Workload , Industrial hygiene
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5138 , http://hdl.handle.net/10962/d1006085 , Work aversion , Mental fatigue , Labor productivity , Employees -- Workload , Industrial hygiene
- Description: Aversion is a complex phenomenon that arises over time through performance of cognitively demanding tasks and has been associated with the mechanisms of mental fatigue and compensatory control. However, little is known about this sensation to dissociate from the task at hand and the causation thereof. It is apparent that aversion is a negative state for the operator and could result in decreased performance and productivity. Through identification of factors that contribute to aversion when performing cognitively demanding tasks, recommendations to reduce design deficits may be employed to promote worker wellbeing and further advance performance and productivity. The current study examined possible factors that may influence aversion experienced through execution of cognitive tasks. A subsequent aim of this study was to assess a possible cause of aversion. The cause of aversion was hypothesized to be related to efficiency, namely the perception of efficiency when performing tasks and actual efficiency calculated through performance of tasks in relation to the expenditure of effort. Four investigations were undertaken with a non-repeated design between investigations and a repeated design within investigations. The first investigation was an analysis of the effect that stimulus cycling had on the aversion experienced. This consisted of a proof reading task with two conditions varying in the repetitiveness of the text, therefore, allowing an analysis as to how aversion is altered by the provision of a new stimulus to the participants. Investigation two investigated the effect that task difficulty imposed on aversion experienced. This comprised of two conditions with varied difficulty that were implemented through a driving simulator tracking task with difficulty altered by the width of the driving lane. The effect of performance feedback on the aversion experienced towards a task was the focus of the third investigation. The effect on aversion experienced was assessed through a driving simulator tracking task with a condition providing feedback of performance to participants and a condition with no knowledge of performance. The final experiment evaluated the effect of task alternations on aversion. This experiment was conducted through alternations between a driving simulator tracking task and a choice reaction task. The choice reaction tasks required participants to identify critical and non-critical stimulus. Four conditions were required for this experiment and were made up of two conditions where there was provision of alternation that varied in frequencies between the two tasks (medium alternation condition and fast alternation condition) and two conditions where no alternations were instated (driving simulator task condition and choice reaction task condition). Separations between all testing conditions were three or more days apart with sixty participants distributed between the investigations. Test duration of each condition was 30 minutes. Subjective data was recorded throughout investigations for all conditions in the form of aversion, subjectively perceived efficiency and rate of perceived exertion. Objective data was collected in the form of physiological responses and performance of tasks for the analysis of objective efficiency. For factors influencing aversion analysis, no differences in aversion experienced were found for the task difficulty and performance feedback investigations. Aversion was found to be less for the changes imposed through the task cycles and task alternation investigations. This concludes that aversion is aggravated through monotonous tasks and by a change of the stimulus or the structure of the cognitive tasks provided to operators; aversion can be alleviated. The results for the cause of aversion analysis found no difference in objective efficiency over time, with a subsequent decrease in perceived efficiency associated with the increasing aversion. Inference from these findings suggest that aversion cannot be attributed to objective inefficiency of task performance, however it can further be assumed that perception of actual efficiency is inaccurate. Perception of efficiency however had a large influence on the sensation of aversion. Aversion is seen to be more of a product of time on task, however whether this is mechanism of fatigue or compensatory control is still to be determined.
- Full Text:
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