The Prisoner’s Dilemma

One method of understanding how individuals and groups behave in social dilemmas is to create such situations in the laboratory and observe how people react to them. The best known of these laboratory simulations is called the prisoner’s dilemma game (Poundstone, 1992).Poundstone, W. (1992). Prisoner’s dilemma. New York, NY: Doubleday. The prisoner’s dilemma gameA laboratory simulation that models a social dilemma in which the goals of the individual compete with the goals of another individual (or sometimes with a group of other individuals). is a laboratory simulation that models a social dilemma in which the goals of the individual compete with the goals of another individual (or sometimes with a group of other individuals). Like all social dilemmas, the prisoner’s dilemma makes use of the assumptions of social learning approaches to behavior that assume that individuals will try to maximize their own outcomes in their interactions with others.

In the prisoner’s dilemma, the participants are shown a payoff matrix in which numbers are used to express the potential outcomes for the each of the players in the game, given the decisions made by each player. The payoffs are chosen beforehand by the experimenter to create a situation that models some real-world outcome. Furthermore, in the prisoner’s dilemma, the payoffs are normally arranged as they would be in a typical social dilemma, such that each individual is better off acting in his or her immediate self-interest, and yet if all individuals act according to their self-interest, then everyone will be worse off.

In its original form, the prisoner’s dilemma involves a situation in which two prisoners (we’ll call them Frank and Malik) have been accused of committing a crime. The police have determined that the two worked together on the crime, but they have only been able to gather enough evidence to convict each of them of a more minor offense. In an attempt to gain more evidence and thus to be able to convict the prisoners of the larger crime, each prisoner is interrogated individually, with the hope that he will confess to having been involved in the more major crime in return for a promise of a reduced sentence if he confesses first. Each prisoner can make either the cooperative choice (which is to not confess) or the competitive choice (which is to confess).

The incentives for either confessing or not confessing are expressed in a payoff matrix such as the one shown in Figure 13.2 "The Prisoner’s Dilemma". The top of the matrix represents the two choices that Malik might make (either to confess that he did the crime or to not confess), and the side of the matrix represents the two choices that Frank might make (also to either confess or not confess). The payoffs that each prisoner receives, given the choices of each of the two prisoners, are shown in each of the four squares.

Figure 13.2 The Prisoner’s Dilemma

In the prisoner’s dilemma, two suspected criminals are interrogated separately. The payoff matrix indicates the outcomes for each prisoner, measured as the number of years each is sentenced to prison, as a result of each combination of cooperative (don’t confess) and competitive (confess) decisions. Outcomes for Malik are in the darker color, and outcomes for Frank are in lighter color.

If both prisoners take the cooperative choice by not confessing (the situation represented in the upper left square of the matrix), there will be a trial, the limited available information will be used to convict each prisoner, and each will be sentenced to a short prison term of 3 years. However, if either of the prisoners confesses, turning “state’s evidence” against the other prisoner, then there will be enough information to convict the other prisoner of the larger crime, and that prisoner will receive a sentence of 30 years, whereas the prisoner who confesses will get off free. These outcomes are represented in the lower left and upper right squares of the matrix. Finally, it is possible that both players confess at the same time. In this case, there is no need for a trial, and in return, the prosecutors offer a somewhat reduced sentence (of 10 years) to each of the prisoners.

Resource Dilemma Games

In addition to the prisoner’s dilemma, social dilemmas have been studied using games in which a group of individuals share a common pool of resources. In these resource dilemma games, the participants may extract or harvest resources from the pool, and it is to their individual advantage to do so. Furthermore, as the resources are used, the pool can replenish itself through a fixed schedule, which will allow the individuals to continue to harvest over long periods of time. Optimal use of the resource involves keeping the pool level up and harvesting only as much as will be replenished in the given time period. Overuse of the pool provides immediate gain for the individuals but has a long-term cost in the inability to make harvests at a later time.

In one version of a resource dilemma game (Edney, 1979),Edney, J. J. (1979). The nuts game: A concise commons dilemma analog. Environmental Psychology and Nonverbal Behavior, 3(4), 252–254. the participants sit around a bowl of metal nuts, and the goal is to get as many nuts as one can. The experimenter adds nuts to the bowl such that the number of nuts in the bowl doubles every 10 seconds. However, the individual players are also motivated to harvest nuts for themselves and are allowed to take out as many nuts as they like at any time. In Edney’s research, rather than cooperating and watching the pool grow, the participants almost immediately acted in their self-interest, grabbing the nuts from the bowl. In fact, Edney reported that 65% of the groups never got to the first 10-second replenishment!

Research Focus

The Trucking Game

Another example of a laboratory simulation that has been used to study conflict is the trucking game. In the original research (Deutsch & Krauss, 1960),Deutsch, M., & Krauss, R. M. (1960). The effect of threat upon interpersonal bargaining. Journal of Abnormal and Social Psychology, 61, 181–189. pairs of women played the trucking game. Each woman was given $4 to begin with and was asked to imagine herself as the owner of one of two trucking companies (Acme or Bolt) that carried merchandise over the roads shown in the figure called “The Road Map From the Trucking Game”. Each time either player’s truck reached the destination on the opposite side of the board, she earned 60 cents, minus operating costs (1 cent for each second taken by the trip). However, the game was also arranged to create the potential for conflict. Each participant wanted to travel on the main road in order to get to the destination faster, but this road was arranged to be so narrow that only one truck could pass at a time. Whenever the two trucks met each other on this narrow road, one of them was eventually forced to back up. Thus there are two choices to getting to the destination. The players had to either take the long, winding roads, thus eliminating their profits (each player would lose 10 cents on each trip if they were forced to take the long road) or figure out a way to share the use of the one-lane road.

Figure 13.3 The Road Map From the Trucking Game

From Deutsch (1973).Deutsch, M. (1973). The resolution of conflict. New Haven, CT: Yale University Press.

Figure 13.4 Outcomes of a Trucking Game Study

Data are from Deutsch and Krauss (1960).Deutsch, M., & Krauss, R. M. (1960). The effect of threat upon interpersonal bargaining. Journal of Abnormal and Social Psychology, 61, 181–189.

Deutsch and Krauss made the game even more interesting by creating experimental conditions in which either or both of the truck company owners had a gate that controlled access to the road. In the unilateral-threat condition, only Acme had a gate. Thus if Bolt attempted to use the main road, Acme could close the gate, forcing Bolt to back up and enabling Acme to reopen the gate and proceed quickly to the destination. In the bilateral-threat condition, both sides had gates, whereas in the no-threat condition, there were no gates.

As shown in the figure titled “Outcomes of a Trucking Game Study,” participants without gates soon learned to share the one-lane road, and, on average, each made a profit. However, threat in the form of a gate produced conflict and led to fewer profits, although in many cases the participants learned to deal with these problems over time and improved their payoffs as the game went on (Lawler, Ford, & Blegen, 1988; Shomer, Davis, & Kelley, 1966).Lawler, E. J., Ford, R. S., & Blegen, M. A. (1988). Coercive capability in conflict: A test of bilateral deterrence versus conflict spiral theory. Social Psychology Quarterly, 51(2), 93–107; Shomer, R. W., Davis, A. H., & Kelley, H. H. (1966). Threats and the development of coordination: Further studies of the Deutsch and Krauss trucking game. Journal of Personality and Social Psychology, 4, 119–126. Participants lost the most money in the bilateral-threat condition in which both sides were given gates that they could control. In this situation, conflict immediately developed, and there were standoffs on the middle road that wasted time and prevented either truck from moving.

Two results of this study are particularly surprising. First, in the unilateral threat condition, both players (including Acme, who had control of the gate) made less money than did those in the no-threat condition (although it is true that in this condition, Acme did lose less than Bolt). Thus being able to threaten the other was not successful for generating overall profits. Second, in the conditions in which both individuals had gates, both individuals actually did worse than they did when only one individual had a gate. Thus when an opponent is able to threaten you, it may be to your benefit to not return with a threat of your own—the ability to counteract the threats of your partner may not always help you but rather may produce even more conflict and losses for both parties.

Who Cooperates and Who Competes?

Although we have to this point focused on how situational variables, such as the nature of the payoffs in the matrix, increase the likelihood that we will compete rather than cooperate, not everyone is influenced the same way by the situation—the personality characteristics of the individuals also matter. In general, people who are more self-oriented are more likely to compete, whereas people who are more other-oriented are more likely to cooperate (Balliet, Parks, & Joireman, 2009; Sagiv, Sverdlik, & Schwarz, 2011).Balliet, D., Parks, C., & Joireman, J. (2009). Social value orientation and cooperation in social dilemmas: A meta-analysis. Group Processes and Intergroup Relations, 12(4), 533–547; Sagiv, L., Sverdlik, N., & Schwarz, N. (2011). To compete or to cooperate? Values’ impact on perception and action in social dilemma games. European Journal of Social Psychology, 41(1), 64–77. For instance, Campbell, Bush, Brunell, and Shelton (2005)Campbell, W. K., Bush, C. P., Brunell, A. B., & Shelton, J. (2005). Understanding the social costs of narcissism: The case of the tragedy of the commons. Personality and Social Psychology Bulletin, 31(10), 1358–1368. found that students who were highly narcissistic (i.e., very highly self-focused) competed more in a resource dilemma and took more of the shared resource for themselves than did the other people playing the game.

Research Focus

Self and Other Orientations in Social Dilemmas

Paul Van Lange and his colleagues (Van Lange, 1999; Van Lange & Kuhlman, 1994)Van Lange, P. A. M. (1999). The pursuit of joint outcomes and equality in outcomes: An integrative model of social value orientations. Journal of Personality and Social Psychology, 77, 337–349; Van Lange, P. A. M., & Kuhlman, D. M. (1994). Social value orientations and impressions of partner’s honesty and intelligence: A test of the might versus morality effect. Journal of Personality and Social Psychology, 67(1), 126–141. have focused on the person determinants of cooperation by characterizing individuals as one of two types—those who are “pro-social,” meaning that they are high on other-concern and value cooperation, and those who are “pro-self” and thus tend to behave in a manner that enhances their own outcomes by trying to gain advantage over others by making competitive choices.

Sonja Utz (2004)Utz, S. (2004). Self-activation is a two-edged sword: The effects of I primes on cooperation. Journal of Experimental Social Psychology, 40(6), 769–776. tested how people who were primarily self-concerned would respond differently than those who were primarily other-concerned when the self-concept was activated. In her research, male and female college students first completed a measure designed to assess whether they were more pro-social or more pro-self in orientation. On this measure, the participants had to make choices about whether to give points to themselves or to another person on a series of tasks. The students who tended to favor themselves were classified as pro-self, whereas those tended to favor others were classified as pro-social.

Then all the students read a story describing a trip to a nearby city. However, while reading the story, half of the students (the self-priming condition) were asked to circle all the pronouns occurring in the story. These pronouns were arranged to be self-relevant and thus to activate the self-concept—“I,” “we,” “my,” and so forth. The students in the control condition, however, were instructed to circle the prepositions, which were not self-relevant (e.g., “of” and “after”).

Finally, the students participated in a series of games in which they had to make a choice between two alternative distributions of points between themselves and another person. As you can see in the following figure, the self-manipulation influenced the pro-self students (who were primarily self-oriented already) in a way that they became even less cooperative and more self-serving. However, the students who were initially pro-social became even more cooperative when the self-concept was activated.

Figure 13.5

Priming the self-concept increased cooperation for those who were other-concerned but increased competition for those who were self-concerned. Data are from Utz (2004).Utz, S. (2004). Self-activation is a two-edged sword: The effects of I primes on cooperation. Journal of Experimental Social Psychology, 40(6), 769–776.

Although it is possible that people are either self-concerned or other-concerned, another possibility is that people vary on both of these dimensions simultaneously, such that some people may be high on both self-concern and other-concern. The dual-concern model of cooperation and competitionThe proposal that individuals will relate to social dilemmas or other forms of conflict in different ways, depending on their underlying personal orientations. (Pruitt & Rubin, 1986)Pruitt, D. G., & Rubin, J. Z. (1986). Social conflict: Escalation, stalemate, and settlement. New York, NY: McGraw-Hill. is based on this approach, and the four resulting personality types are outlined in Figure 13.6 "The Dual-Concern Model".

The dual-concern model suggests that individuals will relate to social dilemmas, or other forms of conflict, in different ways, depending on their underlying personal orientations or as influenced by the characteristics of the situation that orient them toward a given concern. Individuals who are focused primarily on their own outcomes but who do not care about the goals of others are considered to be contending in orientation. These individuals are expected to try to take advantage of the other party, for instance, by withholding their contributions in social dilemmas. Those who are focused primarily on the others’ outcomes, however, will be yielding and likely to make cooperative choices. Individuals who are not concerned about the interests of either the self or others are inactive and unlikely to care about the situation or to participate in solving it at all.

Figure 13.6 The Dual-Concern Model

The interesting prediction of the dual-concern model is that being concerned with one’s own outcomes is not necessarily harmful to the possibility of cooperation. The individuals who are focused on maximizing their own outcomes but who are also concerned with the needs of the others (the problem solvers) are expected to be as likely to cooperate as are those who are yielding. In fact, the dual-concern model suggests that these individuals may be the best negotiators of all because they are likely to go beyond the trap posed by the dilemma itself, searching for ways to produce new and creative solutions through creative thinking and compromise.

Gender and Cultural Differences in Cooperation and Competition

You might be wondering whether men or women are more cooperative. Because women are on average more concerned about maintaining positive relationships with others, whereas men are on average more self-concerned, it might be expected that women might be more likely to cooperate than men. And some research has supported this idea. For instance, in terms of whether or not people accepted an initial offer that was made to them or demanded more, Babcock, Gelfand, Small, and Stayn (2006)Babcock, L., Gelfand, M., Small, D., & Stayn, H. (Eds.). (2006). Gender differences in the propensity to initiate negotiations. Mahwah, NJ: Lawrence Erlbaum. found that about half of the men they sampled negotiated a salary when they took their first job offer, whereas only about one eighth of the women reported doing so. Not surprisingly, women received substantially lower average annual starting salaries than did the men, a fact that is likely to contribute to the wage gap between men and women. And Small, Gelfand, Babcock, and Gettman (2007)Small, D. A., Gelfand, M., Babcock, L., & Gettman, H. (2007). Who goes to the bargaining table? The influence of gender and framing on the initiation of negotiation. Journal of Personality and Social Psychology, 93(4), 600–613. found that, overall, women were less likely than men to try to bargain for personal gain in an experimental task. Small and colleagues concluded that women felt that asking for things for themselves was socially inappropriate, perhaps because they perceive that they have less social power than do men.

Although at least some studies have found that there are gender differences, an interactionist approach to the situation is even more informative. It turns out that women compete less than men in some situations, but they compete about much as men do in other situations. For example, Bowles, Babcock, and McGinn (2005)Bowles, H. R., Babcock, L., & McGinn, K. L. (2005). Constraints and triggers: Situational mechanics of gender in negotiation. Journal of Personality and Social Psychology, 89(6), 951–965. showed that the roles that are activated at the negotiation table (i.e., whether one is negotiating for oneself or on behalf of others) are important triggers for gender differences. Women negotiated as well as men when they were negotiating for others, but they negotiated less strongly than men did for themselves. And Kray, Galinsky, and Thompson (2002)Kray, L. J., Galinsky, A. D., & Thompson, L. (2002). Reversing the gender gap in negotiations: An exploration of stereotype regeneration. Organizational Behavior and Human Decision Processes, 87(2), 386–409. showed that gender differences in negotiation behavior are strongly affected by cognitive constructs that are accessible during negotiation. In general, gender differences in negotiation seem to occur in situations in which other-concern is highly accessible but are reduced or eliminated in situations in which other-concern is less accessible (Gelfand, Major, Raver, Nishii, & O’Brien, 2006).Gelfand, M. J., Major, V. S., Raver, J. L., Nishii, L. H., & O’Brien, K. (2006). Negotiating relationally: The dynamics of the relational self in negotiations. Academy of Management Review, 31(2), 427–451. A recent meta-analysis of 272 research results (Baillet, Li, Macfarlan, & van Vugt, 2011)Balliet, C., Li, N. P., Macfarlan, S. J., & Van Vugt, M. (2011, September 12). Sex differences in cooperation: A meta-analytic review of social dilemmas. Psychological Bulletin. doi: 10.1037/a0025354 found that overall, men and women cooperated equally. But men cooperated more with other men than women cooperated with other women. In mixed-sex interactions, women were more cooperative than men.

And there are also cultural differences in cooperation, in a direction that would be expected. For instance, Gelfand et al. (2002)Gelfand, M. J., Higgins, M., Nishii, L. H., Raver, J. L., Dominguez, A., Murakami, F.,…Toyama, M. (2002). Culture and egocentric perceptions of fairness in conflict and negotiation. Journal of Applied Psychology, 87(5), 833–845. found that Japanese students—who are more interdependent and thus generally more other-concerned—were more likely to cooperate and achieved higher outcomes in a negotiation task than did students from the United States (who are more individualistic and self-oriented; Chen, Mannix, & Okumura, 2003).Chen, Y.-R., Mannix, E. A., & Okumura, T. (2003). The importance of who you meet: Effects of self- versus other-concerns among negotiators in the United States, the People’s Republic of China, and Japan. Journal of Experimental Social Psychology, 39(1), 1–15.