If you've ever felt physically wiped out after a long day sitting at your desk, scientists may have discovered why. 

Thinking hard often triggers feelings of intense frustration, stress and even pain, according to a major new study.

As a result, the Dutch experts behind the research insist that employers should do more to 'reward and support' staff for giving them difficult work.

European workers were more prone to discomfort, compared to those from Asian countries, and 'really dislike mental effort', they added.

The greater the effort, the greater the unpleasantness people experience, said Erik Bijleveld, PhD, of Radboud University in the Netherlands, who led the study. 'When people are required to exert substantial mental effort, you need to make sure to support or reward them for their effort.'

The study, published in the journal Psychological Bulletin, involved meta-analysis of 170 studies, published between 2019 and 2020 and comprising 4,670 participants, to examine how people generally experience mental effort.

They looked at whether mental effort is associated with unpleasant feelings and if those feelings are dependent on the task or the population involved.

A variety of participants were used in the study including health care employees, military employees, amateur athletes and college students from 29 countries.

More than 350 cognitive tasks were involved in the study, such as learning a new technology, finding one’s way around an unfamiliar environment, practicing golf swings and playing a virtual reality game.

In all the studies analysed participants reported the level of effort they exerted as well as the extent to which they experienced unpleasant feelings such as frustration, irritation, stress or annoyance. 

Dr Bijleveld said: 'Managers often encourage employees, and teachers often encourage students, to exert mental effort. 

'On the surface, this seems to work well — employees and students do often opt for mentally challenging activities.

'Although this may lead you to conclude employees and students enjoy thinking hard, the results suggest in general, most people really dislike mental effort.'

The greater the effort, the greater the unpleasantness people experience. 

'It's important for professionals, such as engineers and educators, to keep this in mind when designing tasks, tools, interfaces, apps, materials or instructions.'

The association between mental effort and adverse feelings was less pronounced in studies conducted in Asian countries compared with those in Europe or North America.

Dr Bijleveld suggests this fits the idea that how you respond to mental effort might depend on people’s learning history.

High school students in Asian countries tend to spend more time on schoolwork than their European or North American counterparts and may therefore learn to withstand higher levels of mental exertion early on in their lives, he said.

Despite some tasks being mentally challenging people still voluntarily engage with them, and it could be beneficial for employers to consider this, added Dr Bijleveld. 

'For example, why do millions of people play chess? People may learn that exerting mental effort in some specific activities is likely to lead to reward. 

'If the benefits of chess outweigh the costs, people may choose to play chess, and even self-report that they enjoy chess. 

'Yet, when people choose to pursue mentally effortful activities, this should not be taken as an indication that they enjoy mental effort per se. Perhaps people choose mentally effortful activities despite the effort, not because of it.'