A new review of past research backs up a feeling many of us will have had when trying to figure out a math problem, weigh up the pros and cons of a decision, or work out what's happened in a complicated time travel movie.
It really does hurt to think.
Researchers from Radboud University in The Netherlands say their meta-study's results provide strong evidence that even when we choose to do something that's mentally taxing, it's probably not because we find the effort itself enjoyable.
"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," says psychologist Erik Bijleveld.
"From this, you may be tempted to conclude that employees and students tend to enjoy thinking hard. Our results suggest that this conclusion would be false: in general, people really dislike mental effort."
The team analyzed 170 previous studies published across 2019 and 2020, covering 4,670 participants engaging in 358 different cognitive tasks. While there was plenty of variety in the studies, they all used a standard called the NASA Task Load Index (NASA-TLX) to assess mental workload.
The analysis identified a strong, consistent link between mental effort and unpleasant feelings. As per the NASA-TLX, those feelings can include insecurity, discouragement, irritation, stress, and annoyance.
This association held across different types of task, from conducting a robot-assisted surgery to navigating a virtual train station. It was also evident among different kinds of people, from college students to those in the military.
The greater the mental effort, the greater the unpleasantness. Curiously, the relationship wasn't as strong Asian countries, possibly as a result of longer school hours early in life helping students tolerate mental exertion.
"Our findings show that mental effort feels unpleasant across a wide range of populations and tasks," says Bijleveld.
"This is important for professionals, such as engineers and educators, to keep in mind when designing tasks, tools, interfaces, apps, materials or instructions."
The findings of the study fit in with earlier research, which has shown that difficult mental tasks can cause a sort of brain drain, and that intense concentration for long periods of time can even lead to toxicity in the brain.
So why do people deliberately engage in mentally challenging activities, like chess? The researchers think that it may be because some kind of reward is involved – winning a game, socializing with others, or earning money, for example.
"When people choose to pursue mentally effortful activities, this should not be taken as an indication that they enjoy mental effort per se," says Bijleveld.
"Perhaps people choose mentally effortful activities despite the effort, not because of it."
The research has been published in Psychological Bulletin.