Subjective Workload Assessment Technique Research Articles

Machine learning-based multimodal fusion recognition of passenger ship seafarers’ workload: A case study of a real navigation experiment

Passenger ships have complex transportation systems and seafarers face high workloads, making them susceptible to serious injuries and fatalities in the event of accidents. Existing unimodal workload recognition for seafarers mainly focuses on fixed load induction in bridge simulators, whereas a multimodal approach using multi-sensor data fusion can overcome the reliability and sensitivity limitations of a single sensor. To accurately identify the workload of seafarers, we propose a machine learning-based multimodal fusion method at the feature layer and utilise the Gini index to determine the feature weight of the multimodal data. Through a real ship navigation experiment, the subjective workload assessment technique (SWAT) was employed to collect the continuous workload scores of 24 seafarers in daily tasks. Further, the Dempster–Shafer evidence theory was used to integrate these scores with the unsafe behavior probability of seafarers to obtain a calibrated workload. Electroencephalogram (EEG), electrocardiogram (ECG), and electrodermal activity (EDA) signals were collected in real time, and a high-dimensional feature matrix was extracted to construct the workload recognition model. Random forest, XGBoost, and back-propagation neural networks were used to establish multimodal fusion workload recognition models at the feature-fusion stage, and the model performances were compared. The results showed that the multimodal fusion based on EEG, ECG, and EDA had an excellent recognition accuracy. The XGBoost algorithm has better performance with an accuracy of 85.72%, which is an increment of 9.49% compared to that of the unimodal algorithm, and this improvement passed the statistical significance test. Important features suitable for multimodal fusion recognition were also analysed. The findings of this study have profound significance for enhancing risk control measures pertaining to human factors and ensuring navigation safety.

Common Subjective Mental Workload Assessment Measures: Advantages and Disadvantages

Background: The amount of mental resources required to perform simultaneously a series tasks is considered as mental workload (MWL). High and Low mental workload in the workplace is usually associated with mental fatigue, decreased performance, human error, and even harmful long-term health effects. Among the various MWL assessment techniques, the outcome measures such as questionnaires are easier and more practical in workplace settings. We aimed to compare the three current commonly advocated and used questionnaires. Material and Methods: Three common different outcome measures for evaluation of the MWL are NASA Task Load Index (NASA-TLX), Subjective Workload Assessment Technique (SWAT), and the CarMen-Q workload questionnaire. Among them the NASA-TLX is well known and more popular with six subscales that are used extensively in industrial and official workplaces. SWAT is the simplest one with three dimensions. The NASA-TLX is preferable method because of its higher sensitivity, especially in low MWL conditions. The CarMen-Q questionnaire is a new questionnaire with 29 items and 4 subscales that focuses on cognitive workload and mental fatigue. Conclusion: SWAT is the simplest and less sensitive measure than the NASA-TLX and CarMen-Q questionnaires. In contrast, the NASA-TLX is widely used and more known instrument for MWL evaluation.

Development of a Subjective Workload Assessment Technique Model as an Effort to Improve Performance Nurse in Home Inpatient Room Royal Prima Hospital

It is hoped that the performance of all medical and non-medical personnel at the Hospital will be in top condition. Nurses are expected to provide good service. This research aims to develop a subjective workload assessment technique model as an effort to improve the performance of nurses in the Inpatient Room at Royal Prima Hospital. This research is a quantitative study with a cross sectional study design which was carried out in the inpatient ward of the Royal Prima Hospital from June to July 2023. The population was 120 people. Respondents who were selected (inclusion) or excluded through the selection process were those who had more than 3 months of experience working in a care unit or related work. Data were analyzed univariate, bivariate and multivariate. The results of the research show that there is an influence of time pressure, working hour schedules, multiple roles, revetitive action on improving the performance of inpatient nursing personnel which is subjectively reasoned by inpatient nurses at Royal Prima Hospital. The variable that has the most dominant influence is the dual role variable.The suggestion of this research is that the health service should provide input in the context of continuous guidance to hospitals, especially in managing hospital management to improve better performance.

Analysis of Physical and Mental Workload on Emergency Department (ED) Nurses with Subjective Workload Assessment Technique (SWAT) and Cardiovascular Load (CVL) Methods (Case Study of Sidoarjo City Hospital)

Analysis of Physical and Mental Workload on Emergency Department (ED) Nurses with Subjective Workload Assessment Technique (SWAT) and Cardiovascular Load (CVL) Methods (Case Study of Sidoarjo City Hospital)

Analysis of the Effect of Working Hours on Mental Workload Using the Subjective Workload Assessment Technique Method

This research contains a study of the effect of working hours on mental workload using the Subjective Workload Assessment Technique (SWAT) method. Workload is a consequence of activities given to workers, worker activities can basically be distinguished between physical activities and mental activities. In practice, the workload encountered is a combination of physical workload and mental workload. This study aims to measure mental workload at 10 work stations in the production section at PT Berlian Eka Sakti Tangguh. The SWAT method is a subjective mental workload measurement method based on workers' perceptions. The dimensions are time load, mental effort load and psychological pressure load. The results of the calculation of workload based on SWAT found that the workload category of workers in the production section is at a moderate and high level. The highest workload was experienced at the palm oil storage station (5 workers) at 83.71%. The lowest workload was experienced at the stewing station (3 workers) at 27.36%.

Development and validation of a task load index for process control room operators (PCRO-TLX)

Process control room operators (PCRO) perform a range of complex cognitive safety-critical tasks. The aim of this exploratory sequential mixed methods study was to develop an occupation specific tool to measure the task load of PCRO using NASA Task Load Index (TLX) methodology. Participants were 30 human factors experts and 146 PCRO at two refinery complexes in Iran. Dimensions were developed via a cognitive task analysis, a research review, and three expert panels. Six dimensions were identified: perceptual demand, performance, mental demand, time pressure, effort, and stress. Data from 120 PCRO confirmed that the developed PCRO-TLX has acceptable psychometric properties, and a comparison with the NASA-TLX confirmed that perceptual, not physical, demand was relevant for measuring workload in PCRO. There was a positive convergence of scores of the Subjective Workload Assessment Technique and the PCRO-TLX. This reliable tool (α = 0.83) is recommended for risk assessing the task load of PCRO. Practitioner summary: There are benefits of having a specific tool to measure task load in safety critical roles. Thus, we developed and validated an easy-to-use targeted tool, the PCRO-TLX, for process control room operatives. Timely use and response will assure optimal production alongside health and safety in an organisation. Abbreviations: PCRO: process control room operator; TLX: task load index; PCRO-TLX: process control room operator task load index; NASA-TLX: National Aeronautics and Space Administration task load index; SWAT: subjective workload assessment technique; DALI: driving activity load index; SURG-TLX: surgery task load index; SIM-TLX: virtual reality simulation task load index; VACP: visual, auditory, cognitive and psychomotor; CVI: content validity index; CVR: content validity ratio; RMSEA: root mean square of error approximation; GFI: goodness of fit index; AGFI: adjusted goodness of fit index; CFI: comparative fit index; ANOVA: analysis of variance; CI: confidence interval

Analysis of the Influence of Mental Workload on Employee Performance with the Subjective Workload Assessment Technique (SWAT) Method at PT. Bumi Jasa Utama (Kalla Group)

Purpose: This study aimed to measure the mental workload experienced by employees in the finance department and to analyze the effect of mental workload on employee performance.
 Design/methodology/approach: This study used the Subjective Workload Assessment Technique (SWAT) method to measure the mental workload faced by employees who must perform various activities in their work.
 Findings: The results of this study indicate that the time load factor (T) is the dominant factor affecting employee workload because employees are required in terms of time to perform each activity included in the work process quickly, precisely, and in large quantities every day. Mental workload has a direct and significant positive effect on employee performance.
 Research limitations/implications: Data collection was only conducted on employees of the Finance Department of PT Bumi Jasa Utama.
 Practical implications: Based on the results of this study, the company is expected to increase the number of employees in the finance department to streamline time and minimize the workload of each employee in the finance department. The company is also expected to improve service and service quality by considering employee comfort and performance.
 Originality/value: The condition of employees who are given a high workload and ongoing causes stress and anxiety, so it is necessary to measure mental workload and the effect of mental workload on employee performance.

Develop a Comprehensive Method to Evaluate the Mental Workload of Ship Operators

Mental workload has become an important factor affecting the human error of ship operators. Controlling the mental workload of operators within a reasonable range can reduce human errors. The purpose of this study is to develop an evaluation method to evaluate the ship operator’s mental workload. First, the evaluation indices system was constructed according to three types of mental workload measurements. Second, the criteria importance though intercrieria correlation (CRITIC) method and analytic hierarchy process (AHP) method were used to determine the relative weight of each index. Finally, the fuzzy theory was used to calculate ship operator’s mental workload. The experiment results indicated that subjective workload assessment technique, physiological measurement (eye response), and error rate can be integrated into the comprehensive evaluation method to assess the mental workload of ship operators. Thus, this method can be used to comprehensively evaluate the mental workload level and improve the reliability of the assessment results.

Measurement of student mental workload during online learning using Continuous Subjective Workload Assessment Technique (C-SWAT)

The covid-19 pandemic have effect in Indonesia both financial and non-financial sector include education. There is new habit on education system such as online learning. Since online learning student use gadget/computer to learn. Using gadget in high frequencies may cause effect. This research to measure mental workload of student during online learning in Mechanical Engineering Education Department. Mental effort is measured use continuous subjective workload assessment technique. Continuous subjective workload assessment technique (C-SWAT) is simplify of subjective workload assessment technique. In continuous subjective workload assessment technique, participant is asked dimension that participant prefer, after that participant is asked to do simple arithmetic test. Dimensions are time load, mental effort and psychology-effort. This research use minimum weight of 0 (W0) with weight used is 1/3. Moreover, there is questionnaire to know study interest of participant during online learning. In this research mental effort load is the second highest score, the first highest score is psychology stress effort. Multiplication test is high score than other arithmetic test. During online school student have fatigue, most of them feel eyestrain and body sore. Student prefer synchronous learning type than a-synchronous learning it’s because in synchronous learning student can discus with teacher directly.

A field study of mental workload: conventional bus drivers versus bus rapid transit drivers

Road traffic accidents are increasing worldwide and cause a high number of fatalities and injuries. Mental Work Load (MWL) is a contributing factor in road safety. The primary aim of this work was to study important MWL factors and then compare conventional and BRT (Bus Rapid Transit) drivers' MWL. This study evaluated bus drivers' MWL using the Driving Activity Load Index (DALI) questionnaire conducted with 123 bus drivers in Tehran. The results revealed significant differences between conventional and BRT drivers' mental workload. Moreover, data modelling showed that some organisational and environmental factors such as bus type, working hours per day, road maze, and route traffic volume contribute to drivers' mental workload. These findings suggest some essential customised factors that may help measure and offer practical solutions for decreasing the level of bus drivers' MWL in real-world road driving. Practitioner summary Mental workload is affected by several contributing factors. Depending on the working context, some of these contributing factors have a more significant influence on the level of the experienced MWL. Therefore, the main factors influencing the MWL of BRT and conventional bus drivers were assessed in their real-life environment. Abbreviations: MWL: mental work load; BRT: bus rapid transit; CB: conventional bus; DALI: driving activity load index; NASA-TLX: NASA task load index; SWAT: subjective workload assessment technique; EEG: electroencephalography electrocardiogram; fNIRS: functional magnetic resonance imaging; ITS: intelligent transportation systems; AVL: automated vehicle location

A Framework to Assess Alarm Fatigue Indicators in Critical Care Staff.

OBJECTIVES:This article examines work-related and Personality personality factors that could influence health providers in experiencing alarm fatigue. The purpose of this study is to provide a basis to determine factors that may predict the potential of alarm fatigue in critical care staff.DESIGN:A questionnaire-based survey and an observational study were conducted to assess factors that could contribute to indicators of alarm fatigue.INTERVENTIONS:Factors included patient-to-staff ratio, criticality of the alarm, priority of different tasks, and personality traits.SETTING:The study was conducted at an eight-bed ICU in a mid-size hospital in Montana.SUBJECTS:Data were collected for six day shifts and six night shifts involving 24 critical care professionals. Within each 12-hour shift, six 15-minute intervals were randomly generated through work sampling for 6 days; a total of 1,080 observations were collected.MEASUREMENTS:Alarm fatigue was assessed with the subjective workload assessment technique and Boredom, Apathy, and Distrust Affects, which were measured through validated questionnaires. The Big Five Personality model was used to assess personality traits.MAIN RESULTS:Work factors including task prioritization, nurse-to-patient ratio, and length of shifts were associated with indicators of alarm fatigue. Personality traits of openness, conscientiousness, and neuroticism were also associated.CONCLUSIONS:We recommend assessing personality traits for critical care staff to be aware of how their individualities can affect their behavior towards alarm fatigue. We also recommend an examination of alternative strategies to reduce alarm fatigue, including examining the use of breaks, work rotation, or shift reduction.

Nurses’ Perceptions of Workload Burden in Pediatric Critical Care

Quantifying nurses' perceptions of workload burden when managing critically ill patients is essential for designing interventions to ease nurses' workday. To explore pediatric intensive care unit (PICU) nurses' perceptions of their workload when caring for critically ill patients and managing protocolized therapies. This study was embedded in a multicenter randomized clinical trial where participants were assigned to receive either lower-target or higher-target glucose control. Nurses from 35 participating PICUs completed a baseline survey containing questions about their perceptions of PICU workload in general. They completed an intervention survey after caring for a study patient. Two workload measurement instruments, the Subjective Workload Assessment Technique (SWAT) and the National Aeronautics and Space Administration-Task Load Index (NASA-TLX), were embedded in these surveys. Baseline surveys were completed by 1476 PICU nurses, predominantly female with a bachelor's degree and a median (interquartile range) of 6 (3-11) years of nursing experience and 4 (2-9) years of PICU experience. Most nurses (65%) rated time burden as the most important component of their workload, followed by cognitive (22%) or psychological stress (13%) burden. Work performance was selected most often as contributing to workload, followed by cognitive demand, time pressure, effort, and physical demand. Intervention surveys were completed by 73% of enrolled participants (505 of 693). Nurses managing the lower glucose target group reported higher levels of workload burden as measured by the SWAT (P = .002) and NASA-TLX (P < .001). This study describes the workload burden perceived by PICU nurses when managing critically ill patients in general and when managing protocolized therapies.

Comparison of SAGAT and SPAM for Seeking Effective Way to Evaluate Situation Awareness and Workload During Air Traffic Control Task

Evaluation of air traffic controller’s situation awareness (SA) is becoming important for air traffic management with the growth of air traffic. This study compared two SA evaluation methods: Situation Awareness Global Assessment Technique (SAGAT) and Situation Present Assessment Method (SPAM) to understand how these techniques affect controllers’ predictability in different traffic density settings. Twenty students undertook simple air traffic control simulations by using both techniques. We investigated how these techniques affect their workload with Subjective Workload Assessment Technique (SWAT) and NASA-TLX. SWAT scores showed that high traffic density increased participants’ workload, and extra workload was posed right after answering SA queries. NASA-TLX scores were larger when SAGAT was used than when SPAM was used throughout the simulation. We found that the workload with SAGAT interferes with main tasks more than that of SPAM. The results of query scores suggested that SPAM is more predictive to the assessment of the controller’s SA.

Enhanced cognitive workload evaluation in 3D immersive environments with TOPSIS model

Research puts forward perception-based cognitive workload evaluation methods to help VR developers and users measuring their workload when playing with a VR application. Approaches to measure workload based on biosensors have progressed significantly, while evaluation based on subjective methods still rely on standard questionnaires such as the NASA-TLX table, the Subjective Workload Assessment Technique and the Modified Cooper Harper scale. The pre-defined questions enable operators to carry out experiments and analyse the data more easily than with biofeedback. However, the subjective evaluation process can bias the results because of unperceived internal changes and unknown factors among users. It is therefore necessary to have a method to handle and analyse this uncertainty. We propose to use the Technique for Order Performance by Similarity to Ideal Solution (TOPSIS) model to analyse the NASA-TLX table for measuring the overall user workload instead of using the classical weighted sum method. To show the advantage of the TOPSIS approach, we performed a user experiment to validate the approach and its application to VR, considering factors including the VR platform and the scenario density. Three different weighting methods, including the fuzzy Analytic Hierarchy Process (AHP) from fuzzy logic, the classical weighting based on pairwise comparison and the uniform weighting method, were tested to see the applicability of the TOPSIS model. The results from TOPSIS were consistent with those from other evaluation methods; a significant reduction in the coefficient of variation (CV) was observed when using the TOPSIS model to analyse the NASA-TLX scores, indicating an enhanced precision of the workload evaluation by the TOPSIS method. Our work has a potential application for VR designers and experimenters to compare cognitive workload among conditions and to optimize the settings.

Development and validation of a behavioural video coding scheme for detecting mental workload in manual assembly

Manual assembly in the future Industry 4.0 workplace will put high demands on operators’ cognitive processing. The development of mental workload (MWL) measures therefore looms large. Physiological gauges such as electroencephalography (EEG) show promising possibilities, but still lack sufficient reliability when applied in the field. This study presents an alternative measure with a substantial ecological validity. First, we developed a behavioural video coding scheme identifying 11 assembly behaviours potentially revealing MWL being too high. Subsequently, we explored its validity by analysing videos of 24 participants performing a high and a low complexity assembly. Results showed that five of the behaviours identified, such as freezing and the amount of part rotations, significantly differed in occurrence and/or duration between the two conditions. The study hereby proposes a novel and naturalistic method that could help practitioners to map and redesign critical assembly phases, and researchers to enrich validation of MWL-measures through measurement triangulation. Practitioner summary: Current physiological mental workload (MWL) measures still lack sufficient reliability when applied in the field. Therefore, we identified several observable assembly behaviours that could reveal MWL being too high. The results propose a method to map MWL by observing specific assembly behaviours such as freezing and rotating parts. Abbreviations: MWL: mental workload; EEG: electroencephalography; fNIRS: functional near infrared spectroscopy; AOI: area of interest; SMI: SensoMotoric Instruments, ETG: Eye-Tracking Glasses; FPS: frames per second; BORIS: Behavioral Observation Research Interactive Software; IRR: inter-rater reliability; SWAT: Subjective Workload Assessment Technique; NASA-TLX: National Aeronautics and Space Administration Task Load Index; EL: emotional load; DSSQ: Dundee Stress State Questionnaire; PHL: physical load; SBO: Strategisch Basis Onderzoek

Analisis Beban Kerja Mental Pada Mekanik Menggunakan Metode SWAT dan Metode QNBM

Mental workload is the difference between the demands of a task workload with the maximum capacity of a person's mental capability in a motivated state. The purpose of this study was to determine the level of the mental burden of mechanics using the SWAT and QNBM methods. The results of the Subjective Workload Assessment Technique method for heavy service workload showed that the mechanics were 56.6% burdened. Mental workload dimensions for mechanics 1 and 3 are effort load, for mechanic 2 is time load. The category for light service is 11.11%, unburdened in the time load dimension for all mechanics. Nordic Body Map Questionnaire Method was 67%, with illness category included.

Stretching Interventions and Their Effect on Mental the Workload

Cleaning workers are jobs that require physical strength especially if the work is carried out at a height, and it is not uncommon to complain about musculoskeletal discomfort in physical areas that feel uncomfortable when working in an un ergonomic position. From the observation results If observed posture when cleaning wokers work, body position tilted and bent with angles ranging from 20°-60°, neck bent with an angle of about 20 °, cleaning is done repeatedly by shifting the left hand and right hand with the angle of the upper arm &gt; 90° raised for 10 minutes and forearm around 40°, this illustrates the condition of awkward posture cleaning wokers not ergonomic, posture that is not ergonomic will cause musculoskeletal disorder. The purpose of this research is to measure the effect of stretching on mental workload in an effort to mental recovery. To achieve these objectives, first determine the type of glass cleaning activity outside the building at a height including: preparing tools, climbing stairs, cleaning glass, moving to other areas and cleaning tools, determining stretching movements, then conducting experiments in this case divided into 3 (three) treatment, first without stretching, giving stretching in the morning at 10 am for 6 minutes and stretching during the day at 2 pm for 6 minutes. Measurement of mental workload using the Subjective Workload Assessment Technique (SWAT) method, statistical processing by carrying out the covariance homogeneity test, Multivariate test and followed by the MANOVA test. The results of this research that stretching in addition to having a positive influence on the decline in mental workload, can also be used for mental recovery. Working at a height with a work posture that is not ergonomic, will increase the level of mental workload.

MENTAL WORKLOAD ANALYSIS OF NAVAL CADET ACADEMY USING SUBJECTIVE WORKLOAD ASSESSMENT TECHNIQUE (SWAT) METHODS

There are plentiful activities conducted by the Cadets in order to hold educational process at the NavalAcademy. These activities are particularly vulnerable to physical and psychological friction, especiallyin routine and nurturing activities, where activities in this phase are thought to cause the Cadets toexperience excessive mental workloads which may result in the Cadets being unable to continue theireducation. Therefore, this research would identify one of the factors that were suspected to be thecause of the problem which was psychological factor or mental workload on the Academy of Navalusing Subjective Workload Asessesment Technique (SWAT) method. SWAT method was chosenbecause it was easier to apply and had some advantages in terms of results validity and accuracy, sothat the performance of Cadets expected by Institution were: Tanggap, Tanggon and Trengginas. Theresults of this study indicated that there was a high mental workload for some sub activities at somelevel. The highest mental workload in level I is 69,0 (RPS activity), in level II is 83,4 (senior juniordevelopment), in level III is 77,6 (senior junior development). Besides this research also showed thatthe mental workload between the four levels of Level I, II, III and IV had a significant difference inmental workload in carrying out every activity at the Academy.Keywords: Subjective Workload Assessment Technique (SWAT), Mental Workload, Cadets.

The Watershed Structures in Controlling Runoff - Case Study of Sardasht Basin in IRAN

In order to investigate the performance of constructed structures in Sardasht watershed, Soil and Water Assessment Tools model for simulation of runoff and sediment during the studied period of 1996-2012 was carried out for two cases of existence and absence of flood control structures. From 2007 onwards by performing watershed operations in these sub-basins, the average runoff rate decreased about 250 l/s for sub-basin 1 and 150 l/s for sub-basin 3. This indicates the flood was controlled in these basins. On average, the runoff volume has decreased by 0.25 and 0.15 m3 in the sub-basins 1 and 3 respectively in the presence of the structure compared to the absence of structures. A daily, Monthly simulation time stage and a continuous-time step restrict the usage of the SWAT pattern for comprehensive, occurrence-based flood simulation. The occurrence of acridities and unexpected projections in numerous sectors of IRAN, also the density on basic conveniences precious by mass growth, has owing to a broader difference in deliberation to the problematic of water straight in the alliance. Calibrating a hydrologic model of Sardasht Basin. Using SWAT. Subjective Workload Assessment Technique (SWAT) is a multidimensional scaling method designed to assess time load, mental effort load and stress load. According to the results of Mann-Kendall Test, Watershed management in the Sardasht basin for flood control and runoff can be considered acceptable. Before the watershed operation, the occurrence of runoff with the probability of 80% was zero, which after the operation, the probability of occurrence was reduced by 60%, indicating a positive effect construction of flood and sediment control structures in the Sardasht basin. The results of the hydrological regime curve show that the changes in the monthly runoff ratio to the average monthly runoff before the watershed operations had been more. Due to the limitations, current Soil and Water Assessment Tools simulations in tropical and subtropical regions face a series of problems related to relative humidity, water balance and sediment. Soil and Water Assessment Tools model is also used to estimate the maximum daily flow rate.

THE RELATIONSHIP BETWEEN MENTAL WORKLOAD AND WORK STRESS IN TEACHERS OF SCHOOLS OF DISABLED CHILDREN

A profession as a teacher of schools of disabled children (SLB) is one of the jobs that can cause work stress. Teachers at SLB need more patience, attention, and special skills than teachers in ordinary schools. The purpose of this study was to determine the relationship between mental workload and work stress on SLB teachers in Jombang. This study was an analytical observational study with a cross sectional design. The samples in this study were three out of nine SLBs in Jombang that were chosen through random sampling. The data collection was done by using a questionnaire filled by 33 respondents. The questionnaire included the Subjective Workload Assessment Technique (SWAT) questionnaire to measure mental workload, and The National Union of Teacher (NUT) Stress Survey to measure work stress on SLB teachers in Jombang. The results showed that there was a strong relationship between mental workload and work stress (p-value = 0.049 and r = 0.360). In conclusion, most SLB teachers in Jombang are female and are in the age group of young adults. The Background Education of SLB teachers mostly comes from non-Special Education (PLB) department and the majority of them were new and had been teaching for years. According to the result of this study, the mental workload of SLB teachers in Jombang was at a moderate level, and their work stress was in the low category. Mental workload is one of the factors that can cause work stress on SLB teachers in Jombang.Keywords: mental workload, SLB teachers, work stress