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An interdisciplinary team of researchers at Texas A&M University is taking a new approach to measuring mental fatigue to overcome its subjective nature. | Image: Courtesy of Getty Images

Despite more than a century of studies, the origin and effects of mental fatigue are still under debate in the research community. Mental fatigue is associated with reduced effort on demanding tasks, causing performance and efficiency to decline. Researchers in the Wm Michael Barnes ’64 Department of Industrial and Systems Engineering at Texas A&M University, in collaboration with the Department of Psychological and Brain Sciences and the Department of Engineering Technology and Industrial Distribution, are working to develop a mathematical way to investigate the impact of mental fatigue on effort exertion and decision-making.

Industrial and systems professor Dr. Alfredo Garcia directs this research and works with doctoral student Zhide Wang. Wang said one obstacle in researching mental fatigue is its subjectivity — its effects and symptoms can vary widely across different people. He said a better understanding of mental fatigue’s influence could have both academic and economic impacts as a building block of psychological research.

“Insights about mental fatigue may help explain why people sometimes get bored or distracted in a short time, but in other cases, people can maintain a state of high efficiency without feeling tired,” Wang said. “On the economic side, understanding the mechanism of mental fatigue may help improve the overall efficiency of a system.”

Wang’s model is unique from existing ones because it adopts a framework that relates mental fatigue to the value of decision-making — the perceived value of deciding to complete a task. The researchers hypothesized that mental fatigue discounts the value of a task, making that task not as attractive, which explains why people tend to quit when tired. 

“We proposed a method to determine the value of the task from the subjects’ behaviors and decisions,” Wang said. “Our model embraced the nature of mental fatigue, treating objective measurements as an indicator of subjective fatigue rather than treating the measurement as mental fatigue itself.”

One unexpected observation during the research was a phenomenon Wang called a “learning effect.” When subjects faced a difficult task, their ability to master it through multiple rounds of practice gradually helped increase the task performance regardless of the subject’s mental fatigue over time. These observations urged Wang’s team to revise and refresh their approach for a better and more comprehensive understanding of mental fatigue.

“We can peek into the difficulties faced by mental fatigue researchers,” Wang said. “In addition to mental fatigue, many hidden, unobservable factors may be responsible for human decision-making, and those factors may be highly heterogeneous among people and hard to control.”

The team published their findings recently in the American Psychological Association’s journal Psychological Review. Wang said the next goal is to apply the theory and methods by conducting a series of experiments to examine the validity of the proposed model.

“This work results from a close collaboration between engineering experts and psychologists,” Wang said. “I appreciate my team members for being open to new ideas from different domains and contributing in their own unique ways. The willingness of different communities to talk to each other pushed the project forward and made courageous exploration in the study of mental fatigue.”