Running head: PEERS AND PERSONALITY DEVELOPMENT How Peers Make a Difference: The Role of Peer Groups and Peer Relationships in Personality Development

Peers are a pervasive aspect of people’s lives, but their role in personality development has rarely been considered. This is surprising, given that peers are promising candidates to explain personality development over the entire lifespan. Due to the lack of clear-cut definitions of peers, we first elaborate on their defining criteria and functions in different life phases. We then discuss the role of peers in personality development across the lifespan. We advocate that an integration of social group perspectives and social relationship perspectives is essential to understand peer effects on personality development. Group socialization theory is particularly suited to explain developmental differences between groups as a result of group norms. However, it is blind towards differences in development within peer groups. In contrast, the PERSOC framework is particularly suited to explain individual differences in development within groups as a result of specific dyadic peer relationship experiences. We propose that a conjunct consideration of peer group effects and dyadic peer relationship effects can advance the general understanding of personality development. We discuss examples for a cross-fertilization of the two frameworks that suggest avenues for future research.