Your best friend’s personality can shape your own
University of Zurich
Do the people around us shape our personality? According to the theory of group socialization, our personality is strongly influenced by our desire to belong to and assert ourselves in social groups, such as at university, a period rich with social interaction. However, to date, there has been no strong evidence of a causal link between peer influence and personal development. A study by Ulf Zölitz, professor of economics at the University of Zurich (UZH), and Xiaoyue Shan from the National University of Singapore has now filled this research gap. The researchers conducted a randomized field experiment with undergraduate students, confirming that our personality is malleable and influenced by our peers.
Big Five traits
The researchers’ study involved more than 1,200 students in a popular Bachelor’s degree program in Switzerland. Prior to the study, the students’ personalities were assessed and categorized according to the Big Five traits, i.e. openness, conscientiousness, extraversion, agreeableness and neuroticism. A measure of competitiveness was also included. Participants were then randomly assigned to four-person study groups in which they engaged in frequent study-related interactions over one semester. To assess the long-term effects, the researchers conducted follow-up personality trait surveys for up to four years after the experiment.
More competitive, open and conscientious
The results revealed that students experienced personality “spillovers”: they became more conscientious, open or competitive when grouped with peers who already possessed those traits. However, the researchers found no significant changes in extraversion, agreeableness or neuroticism. “One explanation is that conscientious peers increased the frequency of study-related interactions, reducing stress and anxiety in their group members,” says Ulf Zölitz.
Students were especially likely to adopt traits that are beneficial in academic settings, such as conscientiousness and competitiveness. This supports the concept of motivated personality change, where individuals selectively internalize traits that help them succeed. “Our findings suggest that exposure to peers with productive personality traits can be just as influential as being surrounded by high-performing students,” says Zölitz.
Long-term implications
The long-term surveys confirmed that the spillovers in conscientiousness and competitiveness persisted for up to four years, while the effects of openness diminished over time. “At the individual level, being aware of your peers’ and friends’ personality traits is crucial for your own personal development,” says Zölitz.
At the collective level, personality spillovers have broader implications. This insight could be valuable for policymakers and educators who make decisions about group formation or class assignments, as well as for families choosing schools or neighborhoods. The results also raise important questions about whether economic and social preferences are similarly influenced by the peer environment. Future research could explore how peer groups shape these aspects of individual behavior.
Literature
Xiaoyue Shan, Ulf Zölitz. Peers Affect Personality Development. Review of Economics and Statistics. 28 January, 2025. DOI: https://doi.org/10.1162/rest_a_01557
Contact
Prof. Ulf Zölitz
Department of Economics
University of Zurich
Phone +41 44 634 06 87
E-mail: ulf.zoelitz@econ.uzh.ch
Media Relations
University of Zurich
Phone +41 44 634 44 67
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