Elena Barham

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A Rational Choice Theory of Friendship

  • Faculty Advisor

    Fabrizio Cariani

Published On

May 2017

Originally Published

NURJ 2016-17
Honors Thesis


This thesis blends major philosophic conceptions of friendship with the rational choice framework, seeking to answer the question: what makes friendship rational? Although this question may seem antisocial or socially skeptical, this thesis utilizes game theory and decision theory to argue that a rational interactive strategy for friendship is to be maximally altruistic from the first encounter in the pursuit of honest, deep, robust, and sustained friendships predicated on trust and mutual care. In conducting this investigation, this thesis presents two seminal philosophic conceptions of friendship, arguing for a game theory model of such friendships understood as sustained, mutually altruistic pair dynamics in a stochastic prisoner’s dilemma format. Building from this game theory model, this thesis delves into the role of friendship for the individual as a rational agent, arguing that friendship provides enables a fundamental transformation of the rational capacity of those involved.

INTRODUCTION: Can Friendship Arise from Self-interested Rational Behavior?

Friendships play a central role in our lives. We attend social functions we prefer not to attend, perform inconvenient favors, curb our more critical opinions, all on behalf of the happiness of our friends. This all seems necessary if we assume that friendship is, in some indirect way, “worth it” due to the unconscious reactions of our biological reward system. However, if we look past a biological imperative and treat humans as rational agents, where does that leave us in terms of understanding friendship? In this section, I will explore existing theories relating to the conditions and purpose of friendship and its relationship with rationality.

To evaluate the rationality of friendship, we must assess the conditions that justify sustained altruism to a friend, understanding how individual preferences function and interact within a friendship. Existing theories of friendship suggest that friendship grants both pleasure and usefulness to the friends. Telfer defines the phenomenon of “liking” a friend as a “quasi-aesthetic attitude, roughly specifiable as ‘finding a person to one’s taste.’”[3] However, Telfer acknowledges that this conception of engaging in friendship because one “likes” one’s friend is separate from the bond of friendship. One can imagine individuals that one “likes,” but is not one’s friend, and similarly have friends that (at times) one does not “like.” Moreover, the phenomenon of “liking” seems to not necessarily be rationally justifiable, as two very similar people could be “liked” or “disliked” for subtle reasons unclear even to the individual who holds the preference.

3. Telfer, E. “Friendship.” Proceedings of the Aristotelian Society 71, 1970-71.

Another existing theory highlights the ability of a friend to teach us more about ourselves, that perhaps a close friend makes certain understandings epistemologically accessible to us when they would not be otherwise. Grounded in an Aristotelian discussion of a friend as “a second self,” Cooper posits that one can view a friend objectively enough to discern faults he or she would not find in himself or herself. More concretely, Cooper states that “one recognizes the quality of one’s own character and one’s own life by seeing reflected, as in a mirror, in one’s friend.”[1] In this argument, the ways in which individuals fail to objectively assess their own character can be made accessible to them through similar behavior they analyze objectively in their friend. In this way, friendships are valuable, perhaps necessary, in that they improve our self-knowledge in ways that could arguably enhance one’s rationality. Although this seems plausible, such an intimate understanding of the shortcomings of a friend’s character would be territory of a mature friendship. Seeking to know oneself better fails to explain why one initiates a friendship, and moreover does not clearly support the more frivolous interactions that form the gateway to a deeper friendship.

1. Cooper, J.M., “Friendship and the Good in Aristotle.” Philosophical Review, 86: 1997.

A final account could be that friendship is rational through a “character-relative” or “ethocentric” model as proposed by J.E. Whiting.[4] Friendship, in this view, is based on valuing another individual’s character because they are a certain type of person, such that one considers this “type” good and seeks to emulate this “type” as well. This line of reasoning holds that friendship’s rational justification relies on an individual clearly valuing a friend for the reasons the individual loves herself but avoids the egoist critique by arguing that one does not merely value that this friend is similar to her. Rather, both an individual and this friend are like a certain ideal type of person (in terms of character and values). However, true character and deeply held values are difficult to assess accurately prior to beginning a friendship. It seems unlikely that individuals at the outset of a friendship could really understand these essential traits about their friends. Therefore, this theory provides an explanation for continuing a friendship that is consistent with a rational choice point of view but fails to justify beginning a friendship. Examining friendship in rational choice terms should illuminate the cooperative mechanisms throughout the scope of a friendship.

4. Whiting, J.E. “Impersonal Friends.” Monist 74.1, 1991.

The reasons behind friendship as a concept likewise complicate this investigation. C.S. Lewis posits that friendship relationships are the least necessary of all of our relationships. In The Four Loves, Lewis argues that friendship is free from biological necessity, unlike romantic, kinship, and charitable love.[2] Following this line of thought, rational choice theory would have to answer why we ought to pursue friendship at all. What about friendship justifies its existence, especially if this comes at the expense of time that individuals could be putting into other relationships? This paper will offer a framework to interpret these questions, assessing how our self-interest reflects in our friendships, and in turn, how our friendships manifest our values.

If we posit that friendship demands altruism and that in friendships we must be willing to subjugate our own immediate desires and prioritize those of a friend, there must be a clear individual benefit to friendship to rationally justify these choices. One possible theory of friendship that is compatible with a decision-theory framework would argue that sustained mutual altruism over time evens out or increases the overall utility of both individuals. It could be possible that there are things one friend appreciates more than they cost to the other friend to perform. Perhaps my friend giving me advice costs them a small amount of time and patience, but their advice significantly enhances my ability to navigate a situation. Through exchanging these “social goods,” each friend has a better experience than they would achieve on their own. Thus, although individual altruistic acts may penalize the individual performing them, creating a disposition that encourages the friend’s altruism becomes to one’s overall advantage.

This mutual exchange could happen in a few ways. The first would be immediate gratification—that friendship more or less amounts to a kindness exchange. In this version of friendship, each act of altruism is repaid within a reasonable timeframe; sustained relationships are cases in which two individuals are willing to meet each other’s payback expectations. The second possibility for this could be more long-term, that although friendship demands preliminary sacrifice, there could be a long-run reward to friendship, which the friendly individual thinks merits pursuit. Examples of this version could be eventually having an individual to care for one when one falls sick, or to whom one leaves their children’s custody in the case of a tragedy, who in some sense “owes it” to them to fill this role.

Another explanation for the rationality of friendship falls in line with the valuation of a friend as its own end. In this version, moral, ethical, or other personally held normative judgments compel individuals to form friendships because they feel that they should, that it is the right action to take. A concrete case of this theory would be when an individual maintains social contact with a family friend, not due to organic interest in this person but rather due to a personal belief that she should honor and maintain relationships that are important to her parents out of love for her family. Acting in this way comes with the pleasure of living aligned with one’s principles. In this way, partaking in a friendship supplies utility that makes altruistic acts rational, all things considered. Given this explanation, friendships form between individuals who feel that acting altruistically towards one another is compliant with their moral values and not overpowered by other preferences.

A final defense of the rationality of friendship would be that each individual act of altruism could be explained as constructive of the characteristic dynamics of a friendship, which over time will grow to be its own source of utility for the partaking individuals. In this view, a friend performs a favor for the friend instrumentally to demonstrate trustworthiness, kindness, competence, or some other trait that they feel is important to their friend. Altruistic acts are rational insofar as they construct expectations and mutual understanding so that friendship can develop, with the friendship being enjoyable to the friends in its own right. Over time, these interactions enable both individuals to experience greater happiness than they would without each other’s friendship. This long-term enhanced enjoyment makes it rational to partake in the friendship throughout.

As shown thus far, assuming a rational, self-interested framework for decision-making complicates any explanation for the phenomenon of friendship. This paper will take the requirements of rational choice theory as a tool for analyzing human rationality in both descriptive and action-guiding ways. Rational choice theory describes the broader field of study that comprises decision theory, game theory, and social choice theory. Applying these concepts to friendships provides an avenue to explore the rational motivations behind social behaviors, and what sort of values or beliefs this reveals about individuals who partake in friendship. Moreover, decision theory applied to these questions can serve an action-guiding purpose and allow understanding about ways in which friendships ought to be pursued.

In its full version, this paper uses decision theory to analyze individual decisions within a friendship and proposes a game theory model through which to understand friendship as a series of sustained, cooperative, mutually altruistic interactions. Game theory provides a necessary complement to decision theory as friendship involves multiple agents, and game theory provides better mechanisms to deal with choices that depend on pair dynamics. This paper contributes an understanding of how agents sustain friendship given the self-interest and rationality requirements of rational choice theory and explores what this can tell us about our relationships and our individual selves. I explore a rational choice model to evaluate the rationality of friendship, conceived as a stochastic, extended-form game, and create a stylized toy model to explore generalizable strategy equilibria. Finally, this paper argues for deep, robust friendships (based on Kantian and Aristotelian notions of such) as the most rational relationship an individual can form.

2. Lewis, C.S. The Four Loves. New York: Harcourt, Brace, 1960. Print.


Elena Barham