The Secret to Understanding Others' Personalities?... It's in This Part of the Brain

UNIST Professor Jeong Dong-il's Team Analyzes the Impact of Others' Presence on Decision-Making

Increased Connectivity Between Brain TPJ and mPFC Regions Reflects Others' Tendencies Well... Published in eLife

It has been revealed that people who better reflect others' tendencies in their own decision-making have higher connectivity between specific brain regions.

A research team led by Professor Dongil Jeong from the Department of Biomedical Engineering at UNIST (President Jongrae Park) published their neuroscientific analysis of how the presence of others influences individual decision-making in the international life sciences journal eLife.

Researcher Sun Hee-Young and Professor Jeong Dong-Il (right). Photo by UNIST

According to the study, people adjust their decisions based on whether an observer is risk-averse or risk-seeking. This overturns the prevailing academic consensus that the presence of others simply reinforces risk-seeking choices.

Furthermore, individuals who better incorporate others' tendencies into their own decisions showed higher functional connectivity between the Temporoparietal junction (TPJ) and the Medial prefrontal cortex (mPFC). Functional connectivity refers to the cooperative relationship where different brain regions are simultaneously activated during specific tasks.

First author researcher Heeyoung Seon explained, “Existing theories cannot explain why a young driver who enjoys risky speeding with friends drives ‘at a steady speed’ when accompanied by their parents. This behavioral discrepancy motivated us to start this study.”

The research team conducted a three-stage experiment with 43 participants. In the first stage, participants played a game choosing between a safe option that guaranteed a fixed amount with 100% probability and a risky option with varying probabilities (25%, 50%, 75%) where the amount could differ, measuring their risk preferences.

The second stage involved participants learning about their partners' tendencies. One partner was risk-seeking, and the other was risk-averse. Participants inferred their partners’ choices without prior information and learned through feedback.

In the final third stage, participants played the same game as in stage one under three conditions: with a risk-seeking partner, with a risk-averse partner, or alone without a partner. The experiments in stages one and three were conducted inside a functional MRI (fMRI) scanner to analyze brain activation areas.

Results showed that participants tended to choose the risky option more when the observer was risk-seeking and the safe option more when the observer was risk-averse, compared to when no observer was present. Participants’ behaviors mirrored the observers’ tendencies.

Analysis of fMRI data revealed that the medial prefrontal cortex was activated both when participants were aware of the observer’s presence and when making decisions, while the temporoparietal junction was activated during the decision-making phase.

Moreover, compared to deciding alone, participants who showed increased functional connectivity between these two regions when observed incorporated others’ tendencies more into their own decisions. Both the medial prefrontal cortex and temporoparietal junction are known as parts of the ‘social brain.’

Professor Dongil Jeong stated, “This study suggests that while a person’s inherent preferences cannot be changed, individual decision-making can be altered through social influence.”

The study was published on October 29 and was supported by the National Research Foundation of Korea and the Korea Brain Research Institute.

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