Previous literature on friendship suggests that there are prominent differences between boys’ and girls’ networks. One study showed that, in general, girls’ same-sex dyadic friendships tend to be more exclusive than those of boys (Eder and Hallinan, 1978). There is also evidence that compared to males, females maintain stronger relationships and share higher levels of disclosure (Billy and Udry, 1985). The development of exclusive and stronger relationships among girls may make friendships between girls more conversationally intimate than friendships between boys. On the other hand, compared to girls, boys tend to have a more open network that is less intimate, more volatile, and more likely to include new friends over time (Belle, 1989). In a study of early adolescents, Phillipsen finds that girls report more support in their friendships and have less conflict than do boys (Phillipsen, 1999). A recent qualitative study reports that, although its effects are not totally oppressive, boys’ peer group culture poses obstacles in the development of close friendships because boys feel “the need to protect their vulnerability, prove their masculinity, and preserve their integrity when among their male peers” (Chu, 2005:12). The evidence does not imply that young males do not want to have intimate friendships; rather, they struggle more than girls in their efforts to achieve them.
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Having a best friend has been linked to desirable developmental outcomes (e.g. Hartup, 1993). However, does not only having a perceived friendship, but an actual reciprocated one have further consequences on the well-being of the adolescent? The answer to the question is yes, and in a consistently positive manner. Consistent with Hypothesis 7a, we found strong and consistent effects of reciprocity on feelings of school belonging. Moreover, and in support of Hypothesis 7b, we find strong evidence that adolescents with reciprocated friendships enjoy higher levels of educational outcomes than those whose friendships are not reciprocated. We find that reciprocal friendships as well as those friendships that share more activities have independent and significant effects on students’ GPA. Although a direct effect of reciprocity and grades may be spurious, this suggests that youth who are isolated from peers can suffer dire consequences not only through the lack of peer support, but also through weak ties to their school.

From a study on friendship reciprocity among adolescents and its effect on social outcomes. Click through and scroll down for the conclusions of the study.

Here's hoping Justin Bieber and Taylor Swift have at least one true reciprocated friend, if we learned anything from Entourage it was the value of an intimate posse.