HSE scientists investigate third-party punishment for unfairness

HSE researchers have examined the brain's reaction to violations of social norms and calculated a behavioural index to assess an individual's sensitivity to unfairness. This index can potentially be used to develop individualised rehabilitation programmes for patients with various types of behavioural disorders. The study has been published in Neuroscience Letters.

According to contemporary theories of social structure, the principle of cooperation lies at the foundation of society. Members of a society tend to adhere to established norms and rules to uphold order within their community. Simultaneously, they also monitor other group members’ conformity to the norm. For example, when witnessing an unfair situation, many individuals are prepared to intervene and punish violators. Thus, third-party punishment stands as one of the key regulatory mechanisms in society.

Researchers from the HSE Institute of Cognitive Neuroscience conducted an experiment to examine the underlying neuronal mechanisms involved in third-party punishment. The researchers recruited 20 volunteers and asked them to participate in a 'dictator' game, a popular interactive tool used in social psychology and economics to study social norms in terms of individuals’ perception of fairness.

The participants observed the game as a third party by watching two players on the screen allocate points between them. One of the players—the 'dictator'—allocated the points at their discretion and either distributed them equally or took most for themselves. The study participants had the ability to intervene and punish the ‘dictator’ by spending their own tokens given to them at the beginning of the game. If they chose to punish the 'dictator', their overall winnings would decrease, but fairness would be restored.

The researchers modified the original set-up of the game and introduced a variety of unfair distributions, ranging from extremely unfair (30:10, 35:5, 40:0) to moderately unfair (25:15). There were respective options for the degree of punishment which the 'third-party arbitrator' could apply. During the experiment, EEG recordings were conducted to measure the participants' brain signals in response to unfairness.

"Our results reveal a fascinating picture. On one hand, we have reproduced the findings from earlier studies, showing that a norm violation triggers a signal called MFN (medial frontal negativity). The signal becomes stronger with more blatant observed violations, and the chosen degree of punishment is directly proportional to the signal's strength. However, the picture was not as straightforward in the case of a moderately unfair allocation", says Oksana Zinchenko, co-author of the study and Senior Research Fellow at the HSE Institute of Cognitive Neuroscience.

When the 'dictator' allocated the points at a ratio of 25:15, only 30% of the study participants chose to punish them. The researchers suggest that individuals may exhibit varying sensitivities to social norm violations. People who are more sensitive tend to invest in fairness and to allocate a proportional number of their own tokens based on the severity of the observed violation. In contrast, individuals who are less sensitive do not consistently exhibit a pro-social attitude and are reluctant to consider the extent to which a violator deserves punishment.

"We tested this by calculating the individual behavioural index, ie normalising the number of points that the subjects invested in response to highly unfair allocations (40:0, 35:5) compared to moderately unfair ones (25:15). We found that in more sensitive individuals, the behavioural index was close to 1, while in those less sensitive, it tended towards 0. Next, we computed the correlation between the behavioural index and the amplitude of the EEG signals, demonstrating that the intensity of punishment is linked to individual sensitivity to injustice", explains Zinchenko. 

These findings can be applied in clinical settings to create personalised therapy plans. For instance, in patients with autism spectrum disorders, the degree and depth of their condition may vary, and accordingly, they may require more intensive training in social skills. The researchers suggest that by using the behavioural index, an individualised rehabilitation programme can be constructed for each patient.