Due to the ever-present allure of potentially more appealing or attractive partners, people in mutually committed relationships face a commitment problem (i.e., uncertainty about partner fidelity). This problem exists for both friendship and romantic relationships. In an exploratory pilot study, participants described real-life commitment-confirming incidents in either friendship or romantic relationships. The results revealed that the same types of pro-relationship acts (e.g., throwing a surprise party) were used to communicate commitment to one's partner in both types of relationship. Using signaling theory, we predicted that costly commitment signals would be more effective than non-costly commitment signals (Hypothesis 1). Also, we predicted that failure to engage in such behaviors would communicate non-commitment, and that such failures would have a more detrimental effect on romantic relationships than friendship (Hypothesis 2). Two scenario experiments (study 1 in Japan and study 2 in the U.S.) were conducted to test these hypotheses. The results showed that costly commitment signals were more effective than non-costly commitment signals in both Japan and the U.S. In addition, the absence of situationally appropriate commitment signals (e.g., forgetting a special occasion) was substantially more damaging to romantic relationships than to friendship.
Friendship and romantic relationships (i.e., two types of close non-kin relationships) are associated with a catalog of benefits ranging from increases in self-reported well-being and happiness to improvements in the immune system functioning, lower rates of cardiovascular disease, and reduced mortality (Argyle, 1987, Cacioppo and Patrick, 2008, Holt-Lunstad et al., 2010, House et al., 1988, Jaremka et al., 2014 and Myers and Diener, 1995). Despite these beneficial effects, the effective maintenance of friendship and romantic relationships poses a difficult adaptive problem, the so-called commitment problem ( Frank, 1988, Nesse, 2001 and Schelling, 1960). Suppose that Jessie and Jordan are in a close relationship (gender neutral names are used to emphasize similarities between friendship and romantic relationships). When Jessie encounters a more appealing or attractive relationship partner, Jessie might desert Jordan. The same holds for Jordan. Problematically, the presence of this doubt may deter Jessie and Jordan from deepening their existing relationship. Therefore, in order to maintain a close relationship and to reap benefits from it, both parties must be able to (1) effectively commit themselves to their current partner and (2) credibly communicate this commitment.
Frank (1988) pointed out that certain emotions can help solve the first half of the commitment problem (i.e., the problem of steadfastly committing to one's partner). Love, for example, functions as a commitment device that promotes long-term commitment and, at times, what appears to be irrational devotion (Campbell & Ellis, 2005). Those who are in love tend to devalue attractive potential partners by, for example, paying less attention to them and/or perceiving them as less attractive than they actually are (Gonzaga et al., 2008, Johnson and Rusbult, 1989, Lydon et al., 1999, Maner et al., 2009, Miller, 1997 and Simpson et al., 1990). Other emotions, such as gratitude and guilt, may also serve as a commitment device (Frank, 1988 and Trivers, 1971).
Solving the second half of the commitment problem (i.e., genuinely communicating one's commitment) is more difficult than it might first appear. This is because talk is cheap (Farrell, 1987): Jessie's swearing “best friends forever” or “till death do us part” does not warrant that Jessie will stay in the relationship with Jordan when another more appealing person becomes interested in Jessie. Frank (1988) maintained that the key to solve this second problem lays in emotional expressions that are “hard-to-fake.” Romantic love, for example, is associated with an array of hard-to-fake expressions, such as the Duchenne smile and unconscious gesticulation (Gonzaga et al., 2001 and Gonzaga et al., 2006). Nevertheless, other types of commitment signals have not been well studied. To counteract this imbalance, the present study investigates how commitment to one's friend or romantic partner can be credibly communicated via pro-relationship commitment signaling behaviors.
