The hormone oxytocin influences how the brain learns and recalls information about social hierarchies - who is subordinate to whom and who is on equal footing with whom. A study with this conclusion was published in the journal PNAS. Scientists from South China Normal University (China) and their colleagues from France studied how this hormone changes brain function when learning complex social structures.
The experiment involved 60 healthy young men, but two were excluded due to insufficient accuracy in completing the tasks, so 58 people were included in the final analysis. Participants were randomly divided into two groups: one received a nasal spray with oxytocin, the other a placebo, that is, a spray without an active substance. Then everyone played a computer game in which they had to learn the ranks of employees of two fictitious company departments. In one department the participant himself "worked" (a self-oriented network), in the other - a stranger (an other-oriented network).
During the learning phase, participants saw pairs of faces and guessed which of the two was higher in rank or whether they were equal. After each answer they received feedback - correct or not - and gradually uncovered the hidden structure of the hierarchy. Participants learned ranks in their own department faster than in the other one, and more easily remembered relationships between high- and low-status people than between middle-status people.
Using mathematical modeling, the researchers found that learning is best described by a hybrid model. According to it, people simultaneously track the probability that two people belong to the same rank based on feedback and assign each person a hidden "rank value" that is adjusted over time. In this way the brain builds a holistic representation of the hierarchy without seeing the entire network at once.
While performing the task, brain activity was measured using functional magnetic resonance imaging (fMRI) - it shows which brain areas consume more oxygen, that is, work more actively. When participants correctly chose rank relationships, their activity increased in the ventromedial prefrontal cortex and posterior cingulate cortex - areas associated with processing social information and reward. In those receiving oxytocin, this activity was higher than in the placebo group.
Then came the testing phase, where transitive inferences had to be made - that is, logically deducing relationships between people who were not directly compared. No feedback was given at this stage. It turned out that oxytocin improved the accuracy of inferences about the other department, but not about one's own. At the same time, during the test, participants receiving the hormone showed stronger responses in the amygdala and parahippocampal area - structures involved in processing emotions and memory - when they recalled information about the other network rather than their own.
The authors suggest that oxytocin makes social memory less egocentric, shifting the focus from oneself to others. However, the study has limitations: it involved only healthy men, so the results may not extend to women. In addition, male faces were used, and the method of administering the hormone via nasal spray does not exclude effects on the body bypassing the brain. Further work should test these mechanisms in different groups of people and in real social settings.