A group of researchers from neuroscience and economics at the IMT School of Advanced Studies Lucca has shown, for the first time, in a new multidisciplinary study published in the PNAS magazine, that the debated concept of ‘ego depletion’, that is the diminished willpower, is associated with physical changes in the areas of the brain that rule the executive functions.
In the awake brain, the fatigue seemed to correspond to a rise in the EEG waves typical of sleep in the frontal cortex zone, where the region responsible for decision-making. Theories of this ego depletion first appeared in the scientific literature in the early 2000s. The main focus of the study is that self-control is a limited cognitive resource. The more we use it, the more we exhaust it.
For example, behavioral economics literature has used several types of cognitive manipulations typically in economic games to demonstrate the impact of ego depletion on a bearing including less empathy for others, less tendency to act altruistically, or higher willingness to aggression.
The findings dovetail with a neuroscientific problem that has been considered the classic problem. Sleep research has identified a phenomenon called “local sleep”: this occurs when some brain areas in an awake individual start displaying their recorded EEG typical neural activity during sleep, that is delta waves. Specifically, it was found that this happens most in instances of mental fatigue.
“The brain would be neural evidence of the psychological phenomenon of ego depletion known to psychology,” says Erica Ordali, research fellow at the IMT School and first author of the paper. We next had individuals play games of economically enforced aggression and cooperation including the so-called Hawk and Dove game. There are limited resources to be shared in a hostile environment situation that people can choose to use in either collaborative or overbearing behavior which may lead to loss of resources for both parties in this game.
In a sense, those who had undergone cognitive fatigue were significantly more uncooperative and hostile, compared to a control group not subjected to cognitive fatigue. In particular, the rate of peaceful cooperation decreased from 86% in the “No Fatigue” group to 41% in the “Fatigue” group (p>0.001, for a total of 447 subjects).
Ninety-four participants had electrodes implanted in their heads, that took part in a study involving economic games and underwent electroencephalograms while playing the games. This fits well with the study hypothesis, as fatigued individuals exhibited the emergence of frontal cortical areas with typical sleep waves in some areas but not in others.
“This confirms popular wisdom in the form of the principle of sleeping on it—shown that metabolic exhaustion in some parts of the brain does indeed influence how we come to a decision,” says Pietro Pietrini, who is also Director of the Molecular Mind Lab at the IMT School where the study was devised.
The total number of participants in this study was 447, divided into two studies. Study 1 included 44 participants aged between 22 to 48 years from which 22 were female. Study 2 included 403 participants who are aged between 18 to 34 years, with 251 female participants. Conditions like psychosis which could influence cognitive behavior that were excluded from the study. Pre-screening assessments were evaluated by the participants with prior medical, neurological conditions, and included an online questionnaire.
It suggests hypotheses regarding extraverted self/regulation resource depletion and its consequences for prosocial actions, contributing to the literature findings regarding variation in ego depletion research.
“These findings have crucial implications for many other contexts of daily life, ranging from economic transactions to legal agreements, testing that when our brains are ‘tired,’ we may make choices aligning even with our own worst interests.” More or less the same goes on in most criminal acts as people themselves do concludes Pietrini. The work was led by researchers from the University of Florence and IMT School for Advanced Studies Lucca.
Reference: Ordali E, Marcos-Prieto P, Avvenuti G, et al. Prolonged exertion of self-control causes increased sleep-like frontal brain activity and changes in aggressivity and punishment. Proceedings of the National Academy of Sciences. 2024;121(47). doi: https://doi.org/10.1073/pnas.2404213121Â
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