Cortisol and testosterone associations with social network dynamics

• We examined associations between hormones and social network dynamics.
• Mixed-gender human friendship network was studied.
• Cortisol was positively associated with turn-over of friendships.
• Testosterone was positively related to stability of friendships.
• Individual differences in hormones were related to maintaining and creating friendships.

This study integrates behavioral endocrinology and network science to explore links between hormones and social network dynamics. Specifically, we examine how cortisol (C) and testosterone (T) are associated with creation of new friendships and maintenance of existing friendships. A collegiate marching band was used as a model system of a mixed-sex social organization. Participants (n = 193; 53% female; M age = 19.4 years, 62.1% European-American) provided friendship nominations at time 1 and two months later at time 2. At time 1, participants donated saliva before and after rehearsal (later assayed for C and T). Stochastic actor-based models revealed that individuals with higher C levels were less likely to maintain their social relationships and more likely to create new friendships. In contrast, individuals with higher T levels were more likely to maintain friendships and less likely to create new relationships. Findings suggest that individual differences in C and T are associated with the initiation and maintenance of friendships and have several noteworthy theoretical implications.