Difficulty: Intermediate | Prerequisites: Familiarity with social dilemmas and norms from the Helping and Altruism notes.
Social dilemmas pit individual self-interest against collective welfare. The prisoner's dilemma (two players) and the public goods game (multiple players) model this conflict. Cooperation can be sustained through communication, social norms, reciprocity (tit-for-tat) and punishment. Intergroup conflict is reduced by Allport's contact hypothesis (equal status, common goals, no competition, institutional support), and norms can shift through mass media exposure.
Social dilemma
A situation where an individual's immediate self-interest conflicts with the interests of the collective. When everyone pursues self-interest, everyone is worse off than if all had cooperated. Think of it as: doing dishes, paying taxes, or any case where free-riding is tempting but collectively destructive.
Prisoner's dilemma
A two-person social dilemma. Each player does better by defecting regardless of what the other does, but both are better off if both cooperate. The rational individual choice (defect) produces a collectively irrational outcome.
Public goods game
A prisoner's dilemma with more than two players. Everyone contributes (or not) to a shared pool that is multiplied and redistributed. Free-riding is individually rational but erodes the pool.
Conditional cooperator
Someone who cooperates as long as they believe others are also cooperating. Most people are conditional cooperators, which is why cooperation in repeated public goods games tends to dissolve: a few defectors trigger a cascade.
Tit-for-tat
A reciprocity strategy: cooperate on the first move, then copy whatever the other player did last round. Effective in repeated prisoner's dilemmas.
Contact hypothesis
Allport's proposal that intergroup contact reduces prejudice when four conditions are met: equal status between groups, common goals, absence of intergroup competition and support of authorities, law or custom.
Descriptive norm
What most people actually do. Highlighting widespread bad behaviour (descriptive strong) can backfire by normalising it.
Injunctive norm
What people should do (the rule). Highlighting strong rules against bad behaviour (injunctive strong) decreases bad behaviour.
A social dilemma exists when individual self-interest conflicts with collective welfare. Doing dishes, paying taxes and reducing emissions are everyday examples. When all individuals pursue self-interest, they end up individually worse off than if they had all cooperated.
Prisoner's dilemma: two-person game. Defecting always improves your individual payoff regardless of what the other player does, but mutual cooperation beats mutual defection.
Public goods game: the same logic scaled to more than two players. Withdrawing cooperation punishes cooperators along with defectors, so simple reciprocity (withdrawing cooperation) does not work as well. Selective punishment or norms are needed instead.
In repeated prisoner's dilemmas, tit-for-tat (cooperate first, then mirror the other player) is an effective strategy.
1. Communication
Promise-making. Study: participants played a one-shot public goods game in groups. Half discussed for 10 minutes before deciding; half did not. Discussion produced a carry-over effect of promises and increased cooperation.
2. Social norms
Focusing on normative expectations (rules) and on what other people are doing (if it is positive) can sustain cooperation.
3. Reciprocity
Tit-for-tat in repeated games.
4. Punishment
Sanctions against rule-breakers. Study: participants played a repeated public goods game with or without punishment. In the punishment condition, players could pay $1 from their remaining money to reduce another player's payoff by $3. Results: cooperation was high and rose with each round when punishment was available.
In a one-shot dilemma, there are fewer incentives to cooperate: reciprocity will not matter and reputation matters less. Increasing the salience of norms can increase norm-following.
Study (Arizona petrified forest): four norm messages were tested.
Injunctive weak (positive): a mild reminder of the rule.
Injunctive strong (negative): strong focus on rules against bad behaviour.
Descriptive weak (positive): a mild mention of what others do.
Descriptive strong (negative): strong focus on how many people are doing the bad thing.
Results: descriptive strong (emphasising how many people steal wood) increased bad behaviour by normalising it. Injunctive strong (emphasising the rule against theft) decreased bad behaviour.
Takeaway: negative information is more salient. Highlighting widespread bad behaviour backfires; highlighting rules against it works.
Most people are conditional cooperators: they cooperate as long as they believe others are cooperating too. In repeated public goods games without punishment, cooperation collapses because people react to lower-than-expected cooperation by withdrawing their own. A few defectors set off a downward spiral.
The threat of punishment immediately raises cooperation levels, and punishment leads to sustained cooperation over time. Without punishment, conditional cooperators erode the group's effort.
Allport proposed that intergroup contact reduces prejudice under four conditions:
Equal status between groups.
Common goals.
Absence of intergroup competition.
Support of authorities, law or custom.
In general, contact predicts tolerance. Interracial contact produces numerous benefits, especially through the formation of cross-group friendships.
Common goals study (Indian cricket league)
Researchers randomised cricket teams in India, where a caste system creates deep inter-group divisions.
Results: the more teammates of another caste a player had, the more they wanted to interact with other-caste members in the future and the more they reported them as friends. The more opponents of another caste a player faced, the less they wanted to interact with them and the fewer they reported as friends.
When stakes are involved, common goals increase positive contact, but competition increases negative contact.
Communication between conflicting parties is necessary to resolve disputes. Mass media interventions that transmit norms of reconciliation can reduce conflict. It may be more effective to target perceived social norms than personal beliefs.
Study: different communities were targeted (40 individuals each). Half listened to a "New Dawn" radio show promoting reconciliation norms.
Results: the intervention had no effect on personal beliefs, but it changed perceptions of social norms. The behavioural outcome was telling: when the community decided how to manage a valuable shared resource (the radio), control-group communities quickly handed the decision to the village's local authority, while listener communities deliberated more collectively.
Students often think cooperation always collapses in social dilemmas. It can be sustained through communication, norms, reciprocity and punishment.
Students often think descriptive norms always help. Highlighting widespread bad behaviour (descriptive strong) can normalise it and make things worse.
Students often think the contact hypothesis says any contact reduces prejudice. Contact reduces prejudice only under specific conditions (equal status, common goals, no competition, institutional support).
⚠️ Be able to describe the prisoner's dilemma and the public goods game and explain how they differ.
⚠️ Know the four ways to solve social dilemmas (communication, norms, reciprocity, punishment) with at least one study.
⚠️ Be prepared to describe the petrified forest study and explain why descriptive strong norms backfired.
⚠️ Know Allport's four conditions for the contact hypothesis and be ready to describe the cricket league study.
⚠️ Be able to explain how mass media can change norms (radio study) and the distinction between changing social norms and personal beliefs.
Fill in the blank: A _____ cooperator cooperates only as long as they believe others are also cooperating. (conditional)
True or False: In the petrified forest study, emphasising how many people steal wood reduced theft. (False. It increased theft by normalising it.)
Fill in the blank: The contact hypothesis requires four conditions: equal status, common goals, absence of intergroup competition and _____. (support of authorities, law or custom)
True or False: In the public goods game punishment study, cooperation decreased over rounds when punishment was available. (False. Cooperation was high and rose with each round.)
Q: Compare the prisoner's dilemma and the public goods game. How do strategies for increasing cooperation differ between them?
A: The prisoner's dilemma is a two-person social dilemma; the public goods game extends the same logic to multiple players. In repeated prisoner's dilemmas, reciprocity strategies like tit-for-tat work well because withdrawing cooperation punishes only the defector. In public goods games, withdrawing cooperation also punishes cooperators, so it is less effective. Public goods games require selective punishment (targeting free-riders) or strong norms to sustain cooperation.
Q: How can norm manipulations increase cooperation in a one-shot social dilemma? Describe one study.
A: In one-shot dilemmas, reciprocity and reputation matter less, so making norms salient is key. At the Arizona petrified forest, four norm messages were tested. Descriptive strong (emphasising how many people steal wood) normalised the behaviour and increased theft. Injunctive strong (emphasising rules against theft) decreased theft. The takeaway is that highlighting widespread bad behaviour backfires, while highlighting rules against it works.
Q: What is the contact hypothesis? Describe one study supporting the importance of common goals.
A: Allport's contact hypothesis holds that intergroup contact reduces prejudice under four conditions: equal status, common goals, no competition and institutional support. In a cricket league study in India, teams were randomised across castes. Players with more other-caste teammates reported greater willingness to interact with other-caste members and more cross-caste friendships. Players who faced more other-caste opponents reported the opposite. Common goals (being on the same team) were essential; competition (being on opposing teams) increased negative attitudes.
Social dilemmas connect directly to the economic games in the Helping and Altruism notes (dictator and ultimatum games). Punishment as a cooperation mechanism connects to third-party punishment and parochial altruism. The contact hypothesis connects to prejudice reduction strategies from the Stereotypes and Prejudice notes. Norm manipulation connects to persuasion (how messages change attitudes) from the Persuasion notes.
Social dilemma, prisoner's dilemma, public goods game, cooperation, defection, free-riding, tit-for-tat, reciprocity, communication, social norms, descriptive norms, injunctive norms, punishment, conditional cooperator, contact hypothesis, Allport, equal status, common goals, intergroup contact, cricket league, India, caste, mass media, radio study, norm change, petrified forest, Arizona, conflict resolution, NYU social psychology