Mental fatigue may lead to increased hostility and aggression, according to a new study from Italian researchers. Scientists at the IMT School for Advanced Studies Lucca found that making several difficult decisions in succession can wear down brain areas responsible for self-control, potentially resulting in more aggressive or impulsive behavior.
The study, published Monday in the journal PNAS, provides support for the controversial "ego depletion" theory, which posits that people have limited mental energy for tasks like decision-making or resisting temptations.
Researchers had participants complete an hour-long series of mentally taxing tasks before playing games requiring varying degrees of aggression and cooperation. They measured electrical brain activity during the games and compared results to a control group.
"Our study shows that mental fatigue has a measurable effect on behavior and that, when a certain degree of fatigue sets in, people are more likely to behave in a hostile manner," said Erica Ordali, research fellow at IMT School and lead author of the paper.
The team found that just 45 minutes of executive function tasks like planning and problem-solving increased the likelihood of aggressive acts in social situations. They linked behavioral changes to sleep-like activity in frontal brain areas related to decision-making and impulse control.
Pietro Pietrini, study co-author and director of the Molecular Mind Lab at IMT School, said the findings have implications for everyday situations.
"When the brain is 'tired' we may make choices that go even opposite to our own interests," Pietrini said.
However, not all researchers accept the "ego depletion" theory. A large-scale 2020 study involving over 3,500 participants across 36 laboratories found no evidence of depletion effects after mentally taxing tasks.
The Italian study contributes new evidence to the ongoing scientific debate about mental fatigue and its impacts on behavior. Further research may help clarify the relationship between cognitive exertion and self-control.