Evidence of conditional strategies in human friendship

Many species employ conditional strategies for reproduction or survival. In other words, each individual “chooses” one of two or more possible phenotypes to maximize survival or reproductive advantage given specific ecological niche conditions (e.g., Moran, 1992). Humans seem to employ at least one conditional reproductive strategy, choosing between a more short-term or a more long-term mating strategy (Gangestad & Simpson, 2000), and as with non-human animals, their choices relate in part to an assessment of their own traits (Belsky, 1997; Schmitt, 2005). However, the selection pressures that individuals of a species can exert on each other are not restricted to mate selection; they can arise from many forms of social interaction (West-Eberhard, 1983; Wolf, Brodie, & Moore, 1999). Evidence suggests that individuals are sensitive to characteristics of the self, friend, and environmental conditions when choosing friends (Fehr, 1996; Rose, 1985; Verbrugge, 1977), and that a person’s economic, social, and environmental circumstances influence how they form and organize their friendships (Adams & Allan, 1998; Feld & Carter, 1998). Thus, in this paper I hypothesize that humans have evolved a coherent range of conditional friendship strategies: that we vary predictably in terms of the friendships we form, based on an assessment of our own traits, others’ traits, and our own current needs. I propose a continuum of individual differences in friendship strategy, anchored on one end by those who use friendships for exploration (e.g., skill-building and networking) and on the other end by those who use friendships for intimate exchange (e.g., emotional support and intimacy). I created a measure assessing this continuum, and found that men tended to report a stronger exploration strategy than women. I also found that people with a stronger exploration strategy also had a more short-term mating strategy and were more extroverted, and that people with a stronger intimate exchange strategy reported themselves to be more kind and generous; these results remained when controlling for gender. However, friendship strategy did not relate to socioeconomic status, age, attachment avoidance, relationship status, or presence of kin relationships. There was some evidence that friendship strategy was related to the number of friends an individual reported having and how close they felt to their friends.