Altruistic Punishment in Humans

Ernst Fehr & Simon Gächter

Clemente Jones & Nguyen LamPsychology 459

05/08/2014

Introduction

• Evolution of Human Cooperation:• Kin Selection – Cooperation among genetically close

individuals.• Direct Reciprocity – Selfish incentives for long-term

bilateral cooperation.• Indirect Reciprocity – Cooperators build a reputation.

• ???? – Non-repeated cooperation among genetically unrelated people with no reputation gains.

Solution

• Punishment:– Group better off if free riding is deterred– No one has incentive to punish because it

costs themselves as well as free rider– Punishment of free riders = “Second-order

public good”– Can work if enough people punish free riders

altruistically, with cost and without material benefits for the punishers.

The Question

Do humans engage in altruistic punishment, and if so, how does this inclination affect

the ability of achieving and sustaining cooperation?

Participants

• 240 undergraduate students from the University of Zurich (Switzerland) and the Federal Institute of Technology (Switzerland) voluntarily participated in the experiments.• 31% Females• 69% Males

• Different majors• 33 students – control group for the emotion

questionnaire.

Design• Pre-Study• Participants were randomly assigned to one of ten

experimental sessions (with 24 subjects/session).– 24 subjects allocated to six groups of four.

• Each of the 24 subjects played two 6-period games:– Punishment– No Punishment

• Each participant was placed in front of a computer in a booth such that subjects could not see each other.

Design Cont.• Each member of the group received an endowment of

20 MUs (real monetary stakes) and each one could contribute between 0-20 MUs to a group project.

• For every MU invested in the project, each of the four group members earned 0.4 MUs, regardless of whether he or she made a contribution. – Selfish: 20 MUs– Cooperate: 32 MUs

• Subjects made their investment decisions simultaneously and, once the decisions were made, they were informed about the investments of the other group members.

Condition: Punishment

• Subject could punish each of the other group members after they were informed about the others’ investments.

• A punishment decision was implemented by assigning between 0-10 points to the punished member.

• Each point assigned cost the punished member 3 MUs and the punisher 1 MU.

• Punishment is costly and yield no benefits!

Results• In the 10 sessions, subjects punished other group

members a total of 1,270 times:– 84.3% of the subjects punished at least once.– 34.3% punished more than 5 times.– 9.3% punished more than 10 times.

• The more a subject’s investment fell short of the average investment of the other three group members, the more the subject was punished.

Figure 1

Results Cont.

• The presence of punishers establishes a credible threat that deters non-cooperation:– Punished subjects contribute more in the next

periods.• “The act of punishment, although costly for the

punisher, provides a benefit to other members of the population by inducing potential non-cooperators to increase their investments”.

• The introduction (or elimination) of the punishment opportunity led to an immediate rise (or fall) in investment.

Figure 2a

Figure 2b

Why Punish in a One-Shot Context?

• Negative emotions:–Can trigger a willingness to punish free

riders, despite being costly and yielding no direct benefit.

EmotionsScenario 1 [2]

“You decide to invest 16 [5] francs to the project. The second group member invests 14 [3] and the third 18 [7] francs. Suppose the fourth member invests 2 francs to the

project. You now accidently meet this member. Please indicate your feeling

towards this person.”

EmotionsResults 1 [2]

• Anger/annoyance measured on seven-point scale (1 = ‘not at all,’ 7 = ‘very much’)

• Scenario 1:–47% had anger levels of 6 or 7–37% had anger level of 5

• Scenario 2:–17.4% had anger levels of 6 or 7–80.5% had anger levels of 4 or 5

EmotionsScenario 3 [4]

“Imagine that the other three group members invest 14, 16 and 18 [3, 5 and 7] francs to the project. You invest 2 francs to the project and the others know this. You now accidentally meet one of the other

members. Please indicate the feeling you expect from this member towards you.”

EmotionsResults 3 [4]

• Anger/annoyance measured on seven-point scale (1 = ‘not at all,’ 7 = ‘very much’)

• Scenario 3:–74.5% predicted anger levels of 6 or 7–22.5% predicted anger level of 5

• Scenario 4:–17.8% predicted anger levels of 6 or 7–80% predicted anger levels of 4 or 5

Controlling for Bias

• Same four scenarios presented to 33 subjects that had not participated in the experiments.

• Same emotional patterns from the 240 experimental subjects were expressed in the 33 controls.

Conclusions

• Free riding causes strong negative emotions, which most people expect.

• Most punishment executed by above-average contributors on below-average contributors (74.2%).

• Punishment increases with deviation from the average investment.

• Punishment rendered immediately credible because most people know they trigger negative emotions by free riding:– Punishment opportunity leads to an immediate impact

on contributions (as is evident at switch points between punishment and no-punishment conditions).

Implications

• Altruistic Punishment = key force in establishment of human cooperation.

• There is more at work in sustaining human cooperation than is suggested by kin-selection, direct reciprocity, indirect reciprocity, and costly signaling.

Kin SelectionDirect Reciprocity

Indirect Reciprocity

Kin SelectionDirect Reciprocity

Indirect ReciprocityAltruistic PunishmentAltruistic Punishment

Limitations

• Selective population:– High cognitive ability– W.E.I.R.D.

• Sex Ratio:– 31% Females– 69% Males

• NOT representative of the population