Daily decision-making is never free of some contingent physiological, psychological, or cognitive aspects. This implies that on some occasions, decisions are made which may seem out of the ordinary social behaviour, to the degree that instead of a more satisfying display of cooperation aggressive tendencies arise in the subject.
One of the cognitive mechanisms related to social behaviour that induces most conflicts is the struggle between the internal push towards action and the urge to pull back to think first before taking any cooperative or antisocial action. Research on this tendency however investigated cognitive manipulations usually together with economic games (EG).
A number of such investigations claimed that cooperation was enhanced by intuitive processes while other investigations maintained that cooperation was primarily a consequence of rational processes and that acts of selfishness whether criminal or not were more spontaneous.
A study published in PNAS, and the authors evaluated that engaging for long periods in demanding tasks requiring self-control will eventually lead to fatigue, as reflected by the appearance of physiological sleep-like activity in the prefrontal cortex area of the brain. Aggressive tendencies during the social economic games were, on the contrary, heightened while the state persisted in individuals. In particular, more aggression than usual was noted in the Hawk and Dove game, while the Public Goods Game exhibited a large extent of punishment that was indifferent and spiteful. These results suggest that people may engage less in activities that require them to be altruistic when they are under conditions of cognitive fatigue that preserve the effects of prolonged self-control.
Erica Ordali, research fellow at the IMT School and first author of the paper says, “Our initial assumption was that the phenomenon of local sleep has a basis in the psychological concept of ego depletion.”
In order to test this, the researchers employed an experimental design in which a group of individuals underwent a battery of fatigue-inducing tasks lasting one hour – as opposed to the traditional 15 minutes usually applied in this sort of research – to make the possible effect, if any, more apparent. Next, individuals participated in economic games that invoked varying levels of aggression and cooperation, including the so-called hawk and dove games. In this game, limited resources are to be contested at strife, with options of alliances or aggressiveness that can cause wastage to all involved.
Cognitive fatigue proved to have significant effects on these individuals in that they were much more hostile and uncooperative compared to a control group that was not exposed to cognitive fatigue. In particular, the rate of peaceful cooperation went down from 86% in the ‘No Fatigue’ group to 41% in the ‘Fatigue’ group (p>0.001, total number of subjects 447). All study participants in the experiment (n = 44) performed economics games while their electroencephalograms were taken. Consistent with the hypothesis of the study, areas with sleep waves appeared in some parts of the frontal lobe of sleepy people, which was not present in other parts.
Backed by data collected in this study, we conclude that mental fatigue impacts behaviours and that aggression is more likely amongst people when a certain level of fatigue is reached.
Some limitations of this study should be acknowledged. The behavioural manipulation adopted in the present work was based on previous investigations showing that specific tasks induce changes in local brain activity and behaviour consistent with self-control-related fatigue.
However, it cannot entirely rule out the potential contribution of a general (non-task-specific) mental fatigue related to cognitive demands, as we did not include a control condition requiring similar cognitive efforts but distinct cognitive functions.
To sum up, the present work spans the intricate framework of self-control exertion and social behaviour that is mediated by certain neural mechanisms. We have shown that prolonged self-control exertion can be associated with a decrease in neural firing in the frontal lobes associated with behavioural inhibition and an increase in the likelihood of aggressive behaviours in a given social context.
The result suggests the possible depletion of self-regulatory resources and its effects on the ability in question, which helps understand the ambiguity of results obtained so far in the context of ego depletion research. Indeed, the findings obtain support for the belief in ego depletion as a continuum where its strength is determined by factors such as how long or how intense the previous treatment was, as well as the type of behaviour being studied.
Reference: Ordali, Erica 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).
