A New Method for Inducing Mental Fatigue: A High Mental Workload Task Paradigm Based on Complex Cognitive Abilities and Time Pressure

Abstract

Objectives: With the advancement of modern society, people in cognitively demanding jobs are increasingly exposed to occupational stress. Prolonged and high-intensity cognitive activities are prone to inducing mental fatigue (MF), which adversely affects both psychological and physiological well-being, as well as task performance. Existing methods for inducing MF often demonstrate limited effectiveness due to insufficient cognitive load from overly simplistic tasks and the potential emotional disturbance caused by prolonged task duration. This study aims to explore a comprehensive cognitive task paradigm that integrates task complexity and time pressure, thereby developing a novel and effective method for inducing MF based on high mental workload (HMW) and the effects of time on task (ToT). Methods: Using convenience sampling, university students from a medical college were recruited as participants. The study was conducted in three steps. In the first step, we constructed a 1-back Stroop (BS) task paradigm by designing tasks with varying levels of complexity and incorporating time pressure through experimental manipulation. In the second step, the efficacy of the BS task paradigm was validated by comparing it with the traditional 2-back cognitive task in inducing HMW. In the third step, an MF induction protocol was established by combining the BS task paradigm with the ToT effect (i.e., a continuous 30 min task). Effectiveness was assessed using validated subjective measures (NASA Task Load Index [NASA-TLX] and Visual Analog Scale [VAS]) and objective behavioral metrics (reaction time and accuracy). Statistical analyses were performed using analysis of variance (ANOVA) and t-tests. Results: The BS task paradigm, which integrates complex cognitive abilities such as attention, working memory, inhibitory control, cognitive flexibility, and time pressure, demonstrated significantly higher NASA-TLX total scores, as well as elevated scores in mental demand, temporal demand, performance, and frustration scales, compared to the 2-back task. Additionally, the BS task paradigm resulted in longer reaction times and lower accuracy. As the BS task progressed, participants exhibited significant increases in mental fatigue (MF), mental effort (ME), mental stress (MS), and subjective feelings of fatigue, while the overall number of correct trials and accuracy showed a significant decline. Furthermore, reaction times in the psychomotor vigilance test (PVT) were significantly prolonged, and the number of lapses significantly increased between pre- and post-task assessments. Conclusions: The BS task paradigm based on complex cognitive abilities and time pressure could effectively induce an HMW state. Combined with the ToT effect, the BS paradigm demonstrated effective MF induction capabilities. This study provides a novel and reliable method for inducing HMW and MF, offering a valuable tool for future research in related fields.

Keywords: complex cognitive abilities; high mental workload; mental fatigue; time on task; time pressure.

Figure 1

Experimental flow for validating the effectiveness of the BS cognitive task paradigm in inducing high mental workload.

Figure 2

Experimental flow for validating the effectiveness of the BS cognitive task paradigm in inducing mental fatigue.

Figure 3

1-back Stroop (BS) cognitive task paradigm. Note: 红 (Chinese) = Red (English); 黄 (Chinese) = Yellow (English); 蓝 (Chinese) = Blue (English); 绿 (Chinese) = Green (English).

Figure 4

Comparison of subjective scale indicators for BS cognitive task and 2-back task. Note: Black dots represent the participant data, and the gray-white lines connect the data of the same participant across the two tasks (n = 36). In the box plots, the upper and lower lines of the box represent the upper and lower quartiles, and the middle line represents the median. (A) NASA-TLX total score. (B) Mental demand dimension. (C) Physical demand dimension. (D) Time demand dimension. (E) Performance dimension. (F) Effort dimension. (G) Frustration dimension. NASA-TLX—NASA Task Load Index. * p < 0.05, ** p < 0.01.

Figure 5

Comparison of behavioral indicators for BS cognitive task and 2-back task. Note: Black dots represent participant data, and the gray-white lines connect the data of the same participant across the two tasks (n = 36). In the box plots, the upper and lower lines of the boxes represent the upper and lower quartiles and the middle line represents the median. (A) Reaction time. (B) Accuracy. *** p < 0.001.

Figure 6

Changes in subjective scale scores over task time. Note: The error bar is the standard error. VAS—Visual Analog Scale.

Figure 7

Changes in behavioral performance in BS cognitive task over time. Note: The error bar is the standard error. (A) Correct number of trials. (B) Accuracy rate.

Figure 8

Spearman correlations between subjective and behavioral indicators within different blocks. Note: MF—mental fatigue; ME—mental effort; MS—mental stress; B—boredom; ACC—accuracy. * p < 0.05, ** p < 0.01, *** p < 0.001.

Figure 9

Differential analysis of behavioral indicators between pre- and post-test in PVT. Note: Black dots represent the participant data, and the gray-white lines connect the data of the same participant across the PVT task (n = 72). In the box plots, the upper and lower lines of the boxes represent the upper and lower quartiles and the middle line represents the median. (A) Reaction time. (B) Attention lapse count. ** p < 0.01, *** p < 0.001.