In one of my classes, we play a game known as the Prisoner’s Dilemma. It’s a fun exercise, where students earn ‘points’ by choosing either to cooperate with, or defect on, a partner. We do a few different versions of the game, sometimes with randomly assigned partners for a single round, sometimes with the same partner for multiple rounds, and with different point structures. We also use a deck of playing cards, where students choose a red card to signify defection or a black card for cooperation. All interactions are face-to-face, in real time, and as an incentive there is a prize for the two people who receive the most points.

The main rule of the game is that the number of points one earns depends not only on their own choices, but also the choice their partner makes. The game was originally named after the dilemma that two partners in crime face should they be caught. Here is Eric Johnson’s succinct explanation:

In the game, two people who committed a crime are arrested and each is placed in solitary confinement for interrogation. If one betrays the other, the first goes free while the second is sentenced to three years in prison. If they both betray one another, they each receive two years. But if they both keep silent, they receive the minimum penalty of one year each. Under this scenario, the best individual strategy would be to betray the other. 

In our classroom exercise, we invert the scenario and give positive rewards for cooperating (points), since I’m not authorized to give out negative penalties for defecting like years in prison (not that I’d want to do that, anyway). 

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Under these — somewhat arbitrary — conditions,  the best individual outcome one could hope for when interacting with their partner would be to get the maximum of 5 points. However, the best collective decision would be for both to get 3 points each (or 6 points total for both partners). Mathematically then, the inherent dilemma is whether one should strive to do what is best for oneself or what is best for the collective, all the while not knowing whether to trust one’s partner. 

When the exercise is over, I collect the students’ data sheets which recorded their interactions over multiple rounds and the points they accumulated. I’ll skip over some details, but I wanted to focus on one pattern I found. Generally speaking, the total number of points a person earned was MUCH better correlated with what their partners did than with what they did. The graphs below show the total number of points correlated with the number of red cards (defections) that a student threw, as well as the number of red cards that their various partners (or opponents) threw against them. In other words, there is a lot of luck involved.

Perhaps ‘luck’ isn’t the best word. Instead, we can say that the outcome of our interactions is contingent on others’ choices, and that the locus of control is not completely within ourselves. We are not completely master’s of our own fate. I’ve done this exercise with several classes, and this pattern is very consistent, so this was not just an aberration. We also look at the results as a class and then discuss students’ strategies and motives while the game was underway. Some say that they made a choice to defect at the beginning of the game to avoid being taken advantage of. Others try to read their partners’ faces to predict whether they look trustworthy or not. Still others have no strategy and choose almost randomly. Finally, some wish to establish a reputation as a kind cooperator for the rest of the semester, even if it costs them points and a chance at the prize.

This is just a classroom exercise, and I don’t want to reach too far in looking for lessons that apply to the larger world. Yet, I see parallels in that we are always somewhat dependent on the kindness of strangers (and kith and kin), regardless of our own disposition as cooperators or defectors. 

Ideally, we’d like to find ourselves in a population of cooperators, but we also know that there is always the chance of meeting up with someone unwilling to reciprocate. Therefore, it may be necessary to remain guarded. For example, we may prefer a life of quiet and peace. But that peace can be easily shattered by someone who crashes, uninvited, into our lives — a bully, a hopeful conqueror, or even an otherwise good person who has fallen prey to fear and distrust.

The tricky part is to decide how much to trust, and how guarded we should be. That probably depends on the average tendency of a population to cooperate or defect, as well as our own — imperfect — perceptions of what that tendency really is. But we also know that tendency can fluctuate over time. It is also altered by our own choices because we are, of course, a data-point in the population we live in as well. Fear and distrust can be understandable emotions, and defection a rational choice. But over the long-term they reinforce each other, costing us ‘points,’ dollars, stress, health, and happiness.

World population, or where the humans live.

There are hopeful signs that, overall, we prefer cooperation over defection. One obvious example is that fact that we are an obligatorily social species. People everywhere live in bands, tribes, villages, or mega-cities, strongly suggesting that we must get something out of being near each other, whether it be protection through strength in numbers, or the economic benefits that accompany specialization and trade. To return to Eric Johnson’s article, he wrote that  in actual trials of the prisoner’s dilemma scenario, “people were much more likely to cooperate than would be expected under the assumption of rational self-interest. Cooperation and altruism seem to be innate characteristics of the human species.” Living in an endless cycle of distrust among a population of defectors seems too big a burden to bear. Luckily, we are surrounded by kind, cooperative people as well. Lots of them.  

Finally, it is important to remember that individuals are not locked in to any single behavior. We are not just genetically adapted in the strictest Darwinian sense, but adaptable in that we can assess and respond to our environmental circumstances. And for humans one of the most important environmental variables is the other humans around us. We respond to each other, and others respond to us. In this fascinating interview, the psychologist David Rand noted that there are a handful of variables we can modify which may increase the chances for cooperation:

• Repeated interactions. When we interact repeatedly with the same person, rather than a one-time thing, we may choose cooperation in order to ensure cooperation (and avoid defection against us) in the future.
• Reputation. If people can observe our behavior, we have an incentive to earn a reputation as a cooperator to increase the odds that others will want to cooperate with us in the future. 
• Partner choice. For those with reputations as non-cooperators, people may choose to avoid them altogether. 

While the kindness of strangers is not completely within our control, we can also remember that we are also strangers to others. To them, it is our own willingness to cooperate that is out of their control. When two strangers let their guard down and see through possible distrust, good things can happen.