Motivation depends on how the brain processes fatigue: Researchers

How do we determine whether or not a labor-intensive activity is ‘worth the effort’? The willingness to work is not static, according to researchers from the University of Birmingham and the University of Oxford. It is dependent on the fluctuating rhythms of fatigue.

Fatigue, or the feeling of being exhausted after performing strenuous tasks, is something we all experience on a daily basis. It demotivates us and makes us want to take a break. Although scientists have a good understanding of the mechanisms that the brain uses to determine whether a task is worth the effort, the impact of fatigue on this process is still unknown.

A study was carried out by the research team to see how fatigue affects a person’s decision to exert effort.
They discovered that people who were tired were less likely to work and exert effort, even if it was for a reward.
The findings were published in the journal Nature Communications.

‘We found that people’s willingness to exert effort fluctuated moment by moment, but gradually declined as they repeated a task over time,’ says Tanja Mu?ller, first author of the study, based at the University of Oxford. ‘Such changes in the motivation to work seem to be related to fatigue—and sometimes make us decide not to persist.’

The researchers put 36 young, healthy people through a computer-based task in which they were asked to exert physical effort in exchange for varying amounts of money. The participants completed over 200 trials, during which they were asked whether they would prefer to ‘work’ – which involved squeezing a grip force device – and receive higher rewards, or rest and receive a smaller reward.

The researchers devised a mathematical model to predict how much fatigue a person would experience at any given time during the experiment, as well as how much fatigue would influence their decision to work or rest.

The participants underwent an MRI scan while performing the task, allowing the researchers to look for activity in the brain that matched the model’s predictions.

‘This work provides new ways of studying and understanding fatigue, its effects on the brain, and on why it can change some people’s motivation more than others’ says Dr. Matthew Apps, senior author of the study, based at the University of Birmingham’s Centre for Human Brain Health. ‘This helps begin to get to grips with something that affects many patients’ lives, as well as people while at work, school, and even elite athletes’.