A new study published in the Proceedings of the National Academy of Sciences reveals that prolonged mental fatigue is linked to decreased self-control and increased aggression.

The research introduces the concept of 'local sleep', where specific brain areas display sleep-like wave patterns during wakefulness, particularly under conditions of mental fatigue.

Findings indicate that mental fatigue corresponds to increased EEG waves typical of sleep in the frontal cortex, an area crucial for decision-making.

The implications of this study extend to everyday situations, suggesting that tired brains may lead to decisions that contradict personal interests, especially in economic transactions and legal agreements.

These results support the common advice to 'sleep on it' before making important choices, as mental fatigue can adversely affect decision-making.

Researchers conducted fatigue tasks lasting one hour, significantly longer than the typical fifteen minutes used in previous studies, to enhance observable effects of ego depletion.

After the fatigue tasks, participants engaged in economic games that tested aggression and cooperation, revealing that those experiencing mental fatigue were significantly more hostile.

The cooperation rate dropped dramatically from 86% in the non-fatigued group to 41% in the fatigued group, with this finding being statistically significant across 447 subjects.

The study builds on previous theories of ego depletion, which emerged in the early 2000s, proposing that self-control is a limited cognitive resource that diminishes with use.

However, recent critiques have highlighted challenges in replicating ego depletion effects, prompting further investigation into its neurological underpinnings.

Earlier studies in behavioral economics have explored the effects of ego depletion on empathy, altruism, and aggression, but faced difficulties in consistent replication.

This research was a collaboration with the University of Florence, led by Erica Ordali and co-authored by Pietro Pietrini.