Italian scientists from the Technological School of Advanced Studies of Lucca have found that prolonged mental fatigue can deplete the brain regions responsible for a person's ability to self-control and cause aggressive behavior. The study was published in the scientific journal Proceedings of the National Academy of Sciences (PNAS). During the experiments, experts have identified a phenomenon called “localized sleep”. It occurs when some parts of the brain in the awake person begins to show typical for sleep neural activity in the form of delta waves. To test the hypothesis, the team subjected a test group of people to an intense mental exercise lasting one hour. Compared to a control team that performed the same tasks without overexertion, the participants became twice as aggressive toward each other. “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 engage in hostile behavior,” said the authors of the research paper. According to the scientists, the results provide a scientific basis for the famous saying “the morning is wiser in the evening,” because metabolic exhaustion in certain areas of the brain does affect the quality of decision-making and causes people to make choices that are against their own best interests.