Cultural influences on the measurement of subjective mental workload

Cognitive ergonomics is well entrenched in North American and most European work environments, where systems and products are designed with the capabilities and limitations of the user in mind. A prominent technique for analysing task demands is subjective mental workload measurement. Subjective ratings of mental workload have been shown—in North American and European populations—to be reliable and sensitive to changes in mental workload. However, there is reason to think that cultural differences may affect subjective ratings. This study compared the performance and subjective mental workload ratings of Indonesian (n = 87) and Dutch (n = 88) students in the context of a hybrid memory/visual search task. Performance was comparable for the two groups, but the sensitivity of the subjective workload measures was better in the Dutch than in the Indonesian group. The results are interpreted in light of social axioms and cultural values.

Statement of Relevance: Now more than ever ergonomists must think beyond national borders in improving work processes. Globalisation requires that cultural differences be taken into account in developing and applying ergonomic techniques. This paper presents empirical work showing that cultural differences seriously impact the sensitivity of mental workload measures.     

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.     

Remote collaboration in virtual reality: asymmetrical effects of task distribution on spatial processing and mental workload

In the context of a remote collaboration task in virtual reality, this study aimed to analyze the effects of task distribution on the processing of spatial information and mental workload in spatial dialogs. Pairs of distant participants with specific roles (a guide and a manipulator) had to collaboratively move a virtual object in a plane factory mock-up. The displays allowed the participants to be immersed together in the virtual environment. We analyzed the dialogs that took place according to the frames of reference and the mental transformations required to produce the spatial statements. We also measured the associated mental workload. Results showed that when participants took a perspective, the manipulator’s point of view was preferred. Perspective-taking only yielded a moderate increase in mental rotations, which may explain a specifically high mental demand score for the guides’ NASA-TLX. Overall, this is in accordance with the least collaborative effort principle. This study reinforces the idea that, in collaboration, operators do not need the same aids as each other. Thus, it is not necessary to develop symmetrical tools, i.e., the same tools for all co-workers; instead, the needs of each operator should be taken into account, according to the task he has to perform. In our case, the guides would be helped with perspective-taking aids, while the manipulators would be helped with action-oriented tools.     

The effect of mental workload on the visual field size and shape.

Mental workload is known to reduce the area of one's visual field, but little is known about its effects on the shape of the visual field. Considering this, the visual fields of 13 subjects were measured concurrently under three levels of mental workload using a Goldmann visual perimeter. Tone counting tasks were employed to induce mental workload, avoiding interference with visual performance. Various methods of shape measurement and analysis were used to investigate the variation of the shape of the visual field as a function of mental load. As expected, the mean area of visual fields reduced to 92.2% in the medium workload condition and to 86.41% under heavy workload, compared to light load condition. This tunnelling effect was not uniform, but resulted in statistically significant shape distortion as well, as measured by the majority of the 12 shape indices used here. These results have visual performance implications in many tasks that are susceptible to changes in visual fields and peripheral vision. Knowledge of the dynamics of the visual field as a function of mental workload can offer significant advantages also in mathematical modelling of visual search.     

Taking the load off: investigations of how adaptive cruise control affects mental workload

It has been posited that Adaptive Cruise Control (ACC) represents a new generation of vehicle automation, in that it has the potential to relieve drivers of mental as well as physical workload. The results of previous research however, have raised some confusing issues about the specific effects of Adaptive Cruise Control (ACC) on driver mental workload (MWL)—some studies report reduced MWL compared to manual driving, while others find no effect. Two hypotheses are proposed in an attempt to explain these discrepancies: (a) that any potential MWL reductions due to ACC could be masked by the overriding influence of steering demand; or (b) that the tasks designed in some experiments do not exploit the adaptive nature of the ACC system, therefore precluding any potential benefits. Two related experiments were designed to test these hypotheses. It was found that the main reason for the discrepant findings was the nature of the driving task chosen—constant-speed tasks do not realise the mental workload benefits of ACC. Future researchers using ACC devices are advised to use variable-speed tasks to ensure that all aspects of device functionality are covered.     

Taking the load off: investigations of how adaptive cruise control affects mental workload

It has been posited that Adaptive Cruise Control (ACC) represents a new generation of vehicle automation, in that it has the potential to relieve drivers of mental as well as physical workload. The results of previous research however, have raised some confusing issues about the specific effects of Adaptive Cruise Control (ACC) on driver mental workload (MWL)--some studies report reduced MWL compared to manual driving, while others find no effect. Two hypotheses are proposed in an attempt to explain these discrepancies: (a) that any potential MWL reductions due to ACC could be masked by the overriding influence of steering demand; or (b) that the tasks designed in some experiments do not exploit the adaptive nature of the ACC system, therefore precluding any potential benefits. Two related experiments were designed to test these hypotheses. It was found that the main reason for the discrepant findings was the nature of the driving task chosen--constant-speed tasks do not realise the mental workload benefits of ACC. Future researchers using ACC devices are advised to use variable-speed tasks to ensure that all aspects of device functionality are covered.     

Measuring mental workload with the NASA-TLX needs to examine each dimension rather than relying on the global score: an example with driving

The distinction between several components of mental workload is often made in the ergonomics literature. However, measurements used are often established from a global score, notably with several questionnaires that originally reflect several dimensions. The present study tested the effect of driving situation complexity, experience and subjective levels of tension and alertness on each dimension of the NASA-TLX questionnaire of workload, in order to highlight the potential influence of intrinsic, extraneous and germane load factors. The results showed that, in complex situation, mental, temporal and physical demand (load dimensions) increased, and that novice drivers presented high physical demand when subjective tension was low on performance. Moreover, increase of mental and physical demand increased effort. It thus, appears essential to distinguish the different components of mental workload used in the NASA-TLX questionnaire.

Practitioner Summary: Currently, global score of NASA-TLX questionnaire is used to measure mental workload. Here, we considered independently each dimension of NASA-TLX, and results showed that mental load factors (driving situation complexity, experience, subjective tension and alertness) had a different effect on dimensions, questioning global score use to evaluate workload.     

Analysis of the mental workload of city traffic control operators while monitoring traffic density: A field study

IntroductionIt is important to evaluate when and why the mental workload of operators increases during system operation. The city traffic control center (TCC) is a complex work system, and it is important to describe MW as a condition related to this. The purpose of this study is to evaluate the mental workload of operators while monitoring traffic loads in the city TCC.MethodsElectroencephalography and electrooculography data were collected from 16 operators while performing their daily work, in four conditions: resting state, low traffic density, high traffic density, and recovery. The Simplified-Subjective Workload Assessment Technique (S-SWAT) was used to evaluate the subjective workload of operators.ResultsThe findings indicate that operators experience a larger mental workload during high traffic density than during low traffic density (p < 0.001). TCC stressors led to significant changes in EEG bands, such as theta, alpha, and eye activity. Significant differences were observed for subjective ratings of MW (p < 0.001).ConclusionAlthough the working situations of TCC operators are repeated daily, their mental fatigue and stress level gradually increase, leading to deterioration in their mental health. It may be necessary periodically to monitor their mental health and to consider their organizational behavior during traffic density monitoring.Relevance to industrycomplex work systems have increased the requirement for many operators to conduct mental tasks in real work conditions such as city traffic density monitoring. When evaluating such workplaces, it is important to identify situations requiring increased mental workload that might impose additional stress on operators, decreasing their performance. Based on the results, the traffic control center director would be aware of the MW condition of the operators.     

Employee acceptability of wearable mental workload monitoring: exploring effects of framing the goal and context in corporate communication

Cognition, Technology & Work - Development of wearable mental workload (MWL) measures thrives, especially as leveraged by Industry 4.0. When employees object to wearing such gauges; however,...     

Assessment of workload and arm position during different work sequences: a study with portable devices on construction workers

It is recognised that work related shoulder pain is overrepresented among construction workers compared to other occupations. Studies have shown that working with hands above shoulder level increases the shoulder load. Most studies have been confined to the laboratory. The present project was carried out to map the muscular engagement and postures of construction workers undertaking ceiling fitting, and to compare the results to those of the laboratory studies. Two ambulatory devices were used, one allowing recording of electromyographic (EMG) signals bilaterally from the trapezius muscle, and the other to record the position of both arms and back by means of measuring the angles between the vertical line and the back and both upper arms. These recordings were performed during 1.5–2 h work sequences. The results show that the work was mostly performed in an upright position, that both arms were used to a similar amount and that the workers for a large proportion of their working time had their upper arms at levels that are considered harmful in view of shoulder load. The EMG data showed that nearly 50% of the work was spent with trapezius activity that exceeded that of the reference contraction used (about 15% of maximal voluntary contraction) and that the time spent in muscular relaxation was 10%. It was concluded that the exposure of construction workers undertaking ceiling fitting meets the criteria formulated on the basis of laboratory experiments with respect to a high risk of acquiring chronic shoulder pain, due to rotator cuff tendinitis.     

Partition testing vs. random testing: the influence of uncertainty

This paper compares partition testing and random testing on the assumption that program failure rates are not known with certainty before testing and are, therefore, modeled by random variables. It is shown that under uncertainty, partition testing compares more favorably to random testing than suggested by prior investigations concerning the deterministic case: the restriction to failure rates that are known with certainty systematically favors random testing. In particular, we generalize a result by Weyuker and Jeng (1991) stating equal fault detection probabilities for partition testing and random testing in the case where the failure rates in the subdomains defined by the partition are equal. It turns out that for independent random failure rates with equal expectation, the case above is a boundary case (the worst case for partition testing), and the fault detection probability of partition testing can be up to k times higher than that of random testing, where k is the number of subdomains. Also in a related model for dependent failure rates, partition testing turns out to be consistently better than random testing. The dominance can also be verified for the expected (weighted) number of detected faults as an alternative comparison criterion     

Assessing the determinants of internet banking adoption intentions: A social cognitive theory perspective

Internet banking adoption is one area that has received attention from scholars. The extant studies have mainly used technology acceptance models and behavioural theories which do not account for changes in human behaviour. This study seeks to ascertain the determinants of Internet banking adoption intentions using the social cognitive theory, which accounts for changes in human behaviour. The study selected the sample from bank customers in Ghana through an intercept approach using structured questionnaires. A two stage-approach of confirmatory factor analysis and a structural equation modelling were used in analysing the data. The findings show that websites' social feature, trust, compatibility with lifestyle and online customer services have a significant effect on customers' intentions to adopt Internet banking. However, ease of use did not have a significant relationship with customers' intentions to adopt Internet banking. The significance of the study as well as recommendations for theory, practice and future studies have been discussed.     

Mobile pupillometry in manual assembly: A pilot study exploring the wearability and external validity of a renowned mental workload lab measure

Human operators in the upcoming Industry 4.0 workplace will face accelerating job demands such as elevated cognitive complexity. Unobtrusive objective measures of mental workload (MWL) are therefore in high demand as indicated by both theory and practice. This pilot study explored the wearability and external validity of pupillometry, a MWL measure robustly validated in laboratory settings and now deployable in work settings demanding operator mobility. In an ecologically valid work environment, 21 participants performed two manual assemblies - one of low and one of high complexity - while wearing eye-tracking glasses for pupil size measurement. Results revealed that the device was perceived as fairly wearable in terms of physical and mental comfort. In terms of validity, no significant differences in mean pupil size were found between the assemblies even though subjective mental workload differed significantly. Exploratory analyses on the pupil size when attending to the assembly instructions only, were inconclusive. The present work suggests that current lab-based procedures might not be adequate yet for in-the-field mobile pupillometry. From a broader perspective, these findings also invite a more nuanced view on the current validity of lab-validated physiological MWL-measures when applied in real-life settings. We therefore conclude with some key insights for future development of mobile pupillometry.     

Efficient mining of sequential patterns with time constraints: Reducing the combinations

In this paper we consider the problem of discovering sequential patterns by handling time constraints as defined in the Gsp algorithm. While sequential patterns could be seen as temporal relationships between facts embedded in the database where considered facts are merely characteristics of individuals or observations of individual behavior, generalized sequential patterns aim to provide the end user with a more flexible handling of the transactions embedded in the database. We thus propose a new efficient algorithm, called Gtc (Graph for Time Constraints) for mining such patterns in very large databases. It is based on the idea that handling time constraints in the earlier stage of the data mining process can be highly beneficial. One of the most significant new feature of our approach is that handling of time constraints can be easily taken into account in traditional levelwise approaches since it is carried out prior to and separately from the counting step of a data sequence. Our test shows that the proposed algorithm performs significantly faster than a state-of-the-art sequence mining algorithm.     

Malleable attentional resources theory: a new explanation for the effects of mental underload on performance

This paper proposes a new theory to account for the effects of underload on performance. Malleable attentional resources theory posits that attentional capacity can change size in response to changes in task demands. As such, the performance decrements associated with mental underload can be explained by a lack of appropriate attentional resources. These proposals were explored in a driving simulator experiment. Vehicle automation was manipulated at 4 levels, and mental workload was assessed with a secondary task. Eye movements were also recorded to determine whether attentional capacity varied with mental workload. The results showed a clear decrease in mental workload associated with some levels of automation. Most striking, though, were the results derived from the eye movement recordings, which demonstrated that attentional capacity varies directly with level of mental workload. These data fully supported the predictions of the new theory. Malleable attentional resources theory suggests that future vehicle designers should employ their technology in driver support systems rather than in automation to replace the driver. The implications of this theory are discussed with regard to capacity models of attention as well as to the design of future vehicle systems.     

Indistinguishability operators in measurement theory,Part I: Conversions of indistinguishability operators with respect to scales

For two given ordinal scales in a measurement process, the present paper investigates how an indistinguishability operator evaluated according to one of these ordinal scales can be converted to another indistinguishability operator w.r.t. the other ordinal scale, and establishes the mathematical base of these conversions under the framework of measurement theory [Krantz, D.H., Luce, R.D., Suppes, P., Tversky, A. (1971) Foundations of Measurement, Vol. 1 (Academic Press, San Diego)]. Additionally, this work exposes the rudimentary facts behind the studies in [“Fuzzy Numbers and Equality Relations”, Proc. FUZZ'IEEE 93 (1993) 1298–1301; “Fuzzy Sets and Vague Environments”, Fuzzy Sets and Systems 66 (1994) 207–221; “Fuzzy Control on the Basis of Equality Relations-with an Example from Idle Speed Control”, IEEE Transactions on Fuzzy Systems 3 (1995) 336–350; and “T-partitions of the Real Line Generated by Idempotent Shapes”, Fuzzy Sets and Systems 91 (1997) 177–184], and points out the measurement theoretic derivations of the results in these studies.