Humans are innately social creatures that can never be truly understood without considering their interpersonal relationships. Thus, the Interpersonal Research Lab’s (IRL) research focuses on how behavioral tendencies develop and are expressed within social relationships. The behavioral tendencies that the IRL has examined range from fairly mundane interpersonal behaviors (e.g., acting warmly during an interaction) to behaviors of real life importance (e.g., unhealthy dieting, civic behavior, personality judgment, interpersonal aggression after playing violent video games, etc.). In order to examine how these behavioral tendencies develop and are expressed in social contexts, we have examined a multitude of social relationships (e.g., parent-child relations, peer relationships, romantic relationships, internet interactions, etc.) at different stages of life.