A study published in the April 2013 journal Archives of Sexual Behavior examined the perception of 'to' and 'bottom' roles in gay couples:
In intercourse between men, one of the partners typically assumes the role of an insertive partner (top) while the other assumes a receptive role (bottom). Although some research suggests that the perceptions of potential partners' sexual roles in gay men's relationships can affect whether a man will adopt the role of top or bottom during sexual intercourse, it remains unclear whether sexual roles could be perceived accurately by naïve observers.
In Study 1, we found that naïve observers were able to discern men's sexual roles from photos of their faces with accuracy that was significantly greater than chance guessing.
Moreover, in Study 2, we determined that the relationship between men's perceived and actual sexual roles was mediated by perceived masculinity. Together, these results suggest that people rely on perceptions of characteristics relevant to stereotypical male-female gender roles and heterosexual relationships to accurately infer sexual roles in same-sex relationships. Thus, same-sex relationships and sexual behavior may be perceptually framed, understood, and possibly structured in ways similar to stereotypes about opposite-sex relationships, suggesting that people may rely on these inferences to form accurate perceptions.
