How can I credibly commit to others?

12 May 2018 | Francesca Bonalumi (Central European University)

Imagine that you plan to go to the gym with your friend Kate. You decide together to meet in the locker room at 6pm. Why would you expect that Kate will honour this agreement to meet you at the gym?

Now, imagine that at 5.30pm you discover that some other friends are gathering at 6pm, and you would love to join them. What restrains you from joining them, even if this is now your preferred option? Your answers to these kinds of dilemmas that are faced in everyday life will probably involve some reference to the fact that a commitment was in place between you and Kate.

The notion of a commitment is worth investigating, in part, because it applies to such a wide variety of cases: we are committed to our partners, our faith, our work, our promises, our goals, and even ourselves. Although there is an obvious similarity between all these situations, I will restrict this post to instances of interpersonal commitment, namely those commitments that are made by one individual to another individual (cfr. Clark 2006). 

According to a standard philosophical definition of interpersonal commitment, a commitment is a relation among one committed agent, one agent to whom the commitment has been made, and an action which the committed agent is obligated to perform (Searle 1969; Scanlon 1998).

The ability to make and assess interpersonal commitments is crucial in supporting our prosocial behaviour: being motivated to comply with those courses of action that we have committed to, and being able to assess whether we can rely on others’ commitments, enables us to perform a wide range of jointly coordinated and interpersonal activities that wouldn’t otherwise be feasible (Michael & Pacherie, 2015). This ability requires psychological mechanisms that induce individuals to follow rules or plans even when it is not in their short-term interests: this can sustain phenomena from the inhibition of short-term self-interested actions to the motivation for moral behaviour. 

I will focus on one key, yet underappreciated, aspect of this relation which sustains the whole act of committing: how the committed agent gives assurance to the other agent that she will perform the relevant action. That is, how she makes her commitment credible.

Making a commitment can be defined as an act that aims to influence another agent’s behaviour by changing her expectations (eg my committing to help a friend influences my friend’s behaviour, insofar as she can now rely on my help), and by this act the committer gains additional motivation for performing the action that she committed to (Nesse 2001; Schelling 1980). The key element in all of this is credibility: how do I credibly persuade someone that I will do something that I wouldn’t do otherwise? And why would I remain motivated to do something that is no longer in my interest to do? 

Indeed, a dilemma faced by recipients in any communicative interaction is determining whether they can rely on the signal of the sender (ie how to rule out the possibility that the sender is sending a fake signal) (Sperber et al., 2010). Likewise, in a cooperative context the problem for any agent is how to distinguish between a credible commitment and a fake commitment, and how to signal a credible commitment without being mistaken for a defector (Schelling, 1980).

The most persuasive way to make my commitment credible is to discard alternative options in order to change my future incentives, such that compliance with my commitments will remain in my best interests (or be my only possible choice). Odysseus instructing his crew to tie him to the mast of the vessel and to ignore his future orders is one strong example of committing to resist the Sirens’ call in this manner; avoiding coffee while trying to quit smoking (when having a cigarette after a coffee was a well-established habit) is another example.

How can we persuade others that our commitments are credible when incentives are less tangible, and alternative options cannot be completely removed? Consider a marriage, in which both partners rely on the fact that the other will remain faithful even if future incentives change.

Emotions might be one way of signalling my willingness to guarantee the execution of the commitment (Frank 1998; Hirshleifer 2001). If two individuals decide to commit to a relationship, the emotional ties that they form ensure that neither will reconsider the costs and benefits of the relationship[1].  Likewise, if, during a fight, one individual displays uncontrollable rage, she is giving her audience reason to believe that she won’t give up the fight even if continuing to fight is to her disadvantage. 

One reason that emotions are taken to be credible is because they are allegedly hard to convincingly fake: some studies suggest that humans are intuitively able to recognize the appropriate emotions when observing a face (Elfenbein & Ambady, 2002), and to some extent humans are able to effectively discriminate between genuine and fake emotional expression (Ekman, Davidson, & Friesen, 1990; Song, Over, & Carpenter, 2016).

Formalising a commitment by making promises, oaths or vows is another way of increasing the credibility of your commitment. Interestingly, with such formalised declarations people not only manifest an emotional attachment to the object of the commitment; they also signal a willingness to put their reputation at risk. This is because the more public the commitment is (and the more people are aware of the commitment), the higher the reputational stakes will be for the committed individual.

Securing a commitment by altering your incentives, by risking your reputation, or by expressing it via emotional displays are importantly similar: the original set of material payoffs for performing each action changes, because now the costs of smoking or untying yourself from the mast of a vessel are too high (if it is even still possible to pay these costs). 

But we can imagine the emotional costs paid in case of a failure (eg the disappointment from slipping back into our undesirable habit of smoking), as well as the social costs (e.g. damage to our reputation as a reliable individual), as incentives to comply with the action that was committed to (Fessler & Quintelier 2014).

Fig.1 Payoff matrix of the decision to cheat on your partner: p is the pleasure you get out of cheating, whereas m is the material costs paid in such cases (e.g. a costly divorce), r is the reputational costs and e is the emotional burden that will be paid in such cases. When p is not higher than the sum of r, m and e, and the individual accurately predict the likelihood of these outcomes, we’ll have a situation in which breaking a commitment is not worthwhile.

Consistent with the idea that commitments change your payoff matrix (see Fig.1), several studies have shown that commitments facilitate coordination and cooperation in multiple economic games. Promises were found to increase an agent’s trustworthy behaviour as well as her partner’s predictions about her behaviour in a trust game (Charness and Dufwenberg 2006), and they were found to increase one’s rates of donations in a dictator game (Sally 1995; Vanberg 2008). 

Spontaneous promises have also been found to be predictive of cooperative choices in a Prisoner’s Dilemma game (Belot, Bhaskar & Van de Ven 2010). The willingness to be bound to a specific course of action (eg as Ulysses) has also been found to be highly beneficial in Hawk-Dove and Battle-of-Sexes games, as committed players are more likely to obtain their preferred outcomes (Barclay 2017).

Interestingly, the payoff structures that an agent faces when they make a commitment is similar to the payoff structure of a threat: If you are involved in a drivers’ game of chicken, the outcome you want is the one in which you don’t swerve. But your partner prefers the outcome in which she does not swerve, and the worst outcome would be the one in which the two cars crash because neither of you swerved. The key factor is, again, whether you can credibly signal to the other driver that you won’t spin the wheel, no matter what.

Some of the same means by which credibility can be conveyed in cases commitment apply to threats as well. For instance, one efficacious way by which you can credibly persuade the other driver is by removing the steering wheel and throwing it out of the window, thereby physically preventing yourself from changing the direction of your car (Kahn 1965); another is by playing a war of nerves, conveying the idea that you are so emotionally connected to your goal that you would be willing to pay the highest cost if necessary.

Threat is an interesting phenomenon to consider when investigating the role of credibility in commitment because it might help us to understand how commitment works, and how threat and commitment might have evolved in similar fashion. What leads a non-human animal to credibly signal an intention to behave in a certain way to its audience, and what lead its audience to rely on this signal, is highly relevant for investigating commitment. 

It is still uncertain just how threat signals have stabilized evolutionarily, given that a selective pressure for faking the threat would also be evolutionarily advantageous (Adams & Mesterton-Gibbons 1995). The same selective pressure apply to human threats and commitments: if the goal is to signal future compliance to an action in order to change the audience’s behaviour (by changing her expectations), what motivates us to then comply to that signal instead of, say, simply taking advantage of the change in our audience’s behaviour?

In other words, the phenomenon of commitment is intrinsically tied to the problem of recognising (and maybe even producing) fake signals, and deceiving others, just as in the case of making a threat. That being said, it is worth keeping in mind that the phenomenon of threat differs importantly from the phenomenon of commitment, insofar as the former does not entail any motivation for prosocial behaviour. 

In this respect, the phenomena of quiet calls and natal attraction, in which animals signal potential cooperation or a disposition not to engage in a fight, are also worth investigating further for the sake of better understanding how credibility can be established in the case of commitment (Silk 2001).

Most of our social life is built upon commitments that are either implicit or explicitly expressed. We expect people to do things even in the absence of a verbal agreement to do so, and we act in accordance with these expectations. Investigating the factors that carry this motivational force, such as credibility, is the next big challenge in better grasp the complexities of this important notion, and would help us to better understand its ontogenetic and phylogenetic development.

[1] Indeed, marriage itself may be a way of increasing the likelihood that a commitment will be respected in the future. This is because formalising the relationship in this manner increases the exit costs of a relationship.


Adams, E. S., & Mesterton-Gibbons, M. (1995). The cost of threat displays and the stability of deceptive communication. Journal of Theoretical Biology, 175(4), 405–421.

Barclay, P. (2017). Bidding to Commit. Evolutionary Psychology, 15(1), 1474704917690740.

Belot, M., Bhaskar, V., & van de Ven, J. (2010). Promises and cooperation: Evidence from a TV game show. Journal of Economic Behavior & Organization, 73(3), 396–405.

Charness, G., & Dufwenberg, M. (2006). Promises and Partnership. Econometrica, 74, 1579–1601.

Clark, H. H. (2006). Social actions, social commitments. In S.C. Levinson, N.J. Enfield (Eds.), Roots of human sociality: Culture, cognition and interaction, (pp. 126–150). New York: Bloomsbury.

Ekman, P., Davidson, R. J., & Friesen, W. V. (1990). The Duchenne smile: Emotional expression and brain physiology: II. Journal of Personality and Social Psychology, 58(2), 342–353.

Elfenbein, H. A., & Ambady, N. (2002). On the universality and cultural specificity of emotion recognition: A meta-analysis. Psychological Bulletin, 128(2), 203–235.

Fessler, D. M. T., & Quintelier, K. (2014). Suicide Bombers, Weddings, and Prison Tattoos. An Evolutionary Perspective on Subjective Commitment and Objective Commitment. In R. Joyce, K. Sterelny, & B. Calcott (Eds.), Cooperation and its evolution (pp. 459–484). Cambridge, MA: The MIT Press.

Frank, R. H. (1988). Passion within reason. New York, NY: W.W. Norton & Company.

Hirshleifer, J. (2001). On the Emotions as Guarantors of Threats and Promises. In The Dark Side of the Force: Economic Foundations of Conflict Theory (pp. 198–219). Cambridge, MA: Cambridge University Press.

Kahn, H. (1965). On Escalation: Metaphors and Scenarios. New York, NY: Praeger Publ. Co.

Michael, J., & Pacherie, E. (2015). On Commitments and Other Uncertainty Reduction Tools in Joint Action. Journal of Social Ontology, 1(1).

Nesse, R. M. (2001). Natural Selection and the Capacity for Subjective Commitment. In R. M. Nesse (Ed.), Evolution and the Capacity for Commitment (pp. 1–43). New York, NY: Russell Sage Foundation.

Sally, D. (1995). Conversation and cooperation in social dilemmas a meta-analysis of experiments from 1958 to 1992. Rationality and society, 7(1), 58–92.

Scanlon, T. M. (1998). What We Owe to Each Other. Cambridge, MA: Harvard University Press.

Schelling, T. C. (1980). The Strategy of Conflict. Cambridge, MA: Harvard University Press.

Searle, J. R. (1969). Speech Acts: An essay in the philosophy of language. Cambridge, MA: Cambridge University Press.

Silk, J. B. (2001). Grunts, Girneys, and Good Intentions: The Origins of Strategic Commitment in Nonhuman Primates. In R. M. Nesse (Ed.), Evolution and the Capacity for Commitment (pp. 138–157). New York, NY: Russell Sage Foundation.

Song, R., Over, H., & Carpenter, M. (2016). Young children discriminate genuine from fake smiles and expect people displaying genuine smiles to be more prosocial. Evolution and Human Behavior, 37(6), 490–501.

Sperber, D., Clément, F., Heintz, C., Mascaro, O., Mercier, H., Origgi, G., & Wilson, D. (2010). Epistemic vigilance. Mind and Language, 25(4), 359–93.

Vanberg, C. (2008). Why Do People Keep Their Promises? An Experimental Test of Two Explanations. Econometrica, 76(6), 1467–1480.