A cross-sex friendship is a platonic relationship between two unrelated people of differing sexes or gender. There are multiple types of cross-sex friendships, all defined by whether or not each party has a romantic attraction to each other, or perceives that the other is interested. A few theories have been developed to explain the existence of such friendships. Research has been done on why men and women initiate these relationships, how they are perceived by others, implications for children with cross-sex friendships, among others. Cross-sex friendships can also create problems for those involved if either or both have or ever had any romantic feelings for the other. Background Cross-sex friendships play a large role in social relations of both men and women. They can be a cause of complications because of the potential for romance or sexual interactions. Monsour (2002) defines a cross-sex friendship as a “voluntary, non-familial, non-romantic, relationship between a female and a male in which both individuals label their association as a friendship”. However, just because these friendships are labeled as “non-romantic,” one cannot assume that there are no romantic or sexual undertones. Guerrero and Chavez (2005) suggest that there are four types of cross-sex friendships: mutual romance, strictly platonic, desires romance, and rejects romance. In a “mutual romance” cross-sex friendship, one of the participants wants a romantic relationship with the other individual and believes that the other individual wants the same. In “strictly platonic” relationships, the individual believes that the other simply wants to be just platonic friends with no thought of romance. In a "desires romance" cross-sex friendship, one individual wants the friendship to become a romantic relationship but does not believe the other individual wants a romantic relationship. In a “rejects romance” cross-sex relationship, one individual does not want the relationship to turn romantic, but believes that their friend does. Each of these friendship styles are based on the goals and viewpoint of the individual. Other theories and research discuss the causes and benefits of cross-sex friendships. Major theories Evolutionary theory Bleske-Rechek et al. (2012) theorize that cross-sex friendships are a part of humans’ evolved mating strategies. Current mating strategies unconsciously motivate individuals to enter into cross-sex friendships because it gives them more opportunities to mate. As a result, individuals within these cross-sex friendships often develop attraction to the other individual, even when that attraction is completely unintended. This evolutionary theory predicts that cross-sex