Communication and Cooperation in Social Dilemmas

Susanne Abele, Garold Stasser & Christopher Chartier

Miami University

Communication and Cooperation in Public Good Games

• Public good provision– Public radio, public transportation– Collective and personal interests at odds

• How can cooperation be increased?– Communication

• Kerr & Kaufmann-Gilliland (1994)• Kerr et al. (1997)

Communication and Cooperation in Public Good Games

• Examples where communication did not help– Chen & Komorita (1994)

• Signals need to be binding

– Wilson & Snell (1997)• Nonbinding signals decreased cooperation

• How do we rectify these seemingly contradictory results?

Communication and Cooperation in Public Good Games

• Many differences between studies– Nature of communication– Specifics of endowments and payoffs

– Type of public good game• Kerr & Kaufmann Gilliland (1994), Kerr et al. (1997)

– Step-level (minimal contributing set game)• Chen & Komorita (1994), Wilson & Snell (1997)

– Continuous public good game

Continuous Public Good Games

• Players receive endowment– Allocate to public account or private account

• Contributions to public account earn interest• Players are always better off keeping a unit in

their private account instead of contributing• Nash equilibrium = all players contribute

nothing

Step-Level Public Good Games

• Players receive endowment– Allocate to public account or private account

• Provision point– Public good provided if met or exceeded– If not met, contributions are lost

• Players are not always better off withholding contributions

Step-Level Public Good Games

• 4 players with 10 unit endowments• 40 unit bonus if 20 units are contributed• 3 players contribute 19 total units

– If player 4 contributes 1 unit, they earn 19 units– If player 4 contributes nothing, they earn 10 units

• Many Nash equilibria– All players contribute nothing– Contributions exactly meet the provision point

Minimal Contributing Set Games

• Type of step-level game• Players have a dichotomous decision

– Contribute full endowment or nothing

• Provision point specifies how many players must contribute

Important Difference between Continuous and Step-Level Games

• Step-level games (including MCS games) provide the opportunity for coordinated solutions

• Continuous games do not

• This difference can lead to differential effects of communication on cooperation

Experimental Design

• 2 (Type of Game: Continuous Public Good Game versus Minimal Contributing Set Game)

X 2 (Communication: tentative decision communicated versus no communication)

Procedure

• Groups of 4 with 10 unit endowments• Continuous game

– Public account earned 100% interest (doubled)• MCS game

– Provision point of 20 units, earned a 60 unit bonus• Communication

– Message of tentative decision before trial– All players received all messages before deciding

• 12 trials

Giving by Trial Block

Game: Continuous Min SetControl Cheap

Mea

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Control Cheap

Block 3 Giving

Game: Continuous Min Set

Mea

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per

Tria

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Giving and Pledges by Trial Block

Game: Continuous Min SetPledge Give

Mea

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g/P

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Pledge Give

Giving and Pledges

• MCS game– Pledged an excess of contributions on an average

of 5 trials– When pledges exceeded provision point, the

mean difference between pledges and contributions was 4.5

– When they did not, it was 1.1

• Continuous game– Control groups earned more than pledging groups

Perception of Games

Players in a Minimal Contributing Set Game saw each other as more cooperative than did players in a Continuous Public Goods Game by endorsing statements like: ‘My group tried to earn as much as possible for all of us.’ ‘My group tried to keep the differences in our earnings as small as possible.’‘The members of my group tried to help each other.’

Conclusions

• Non-binding pledges hurt cooperation in continuous game– Pledge high, contribute low

• Opportunity for coordinated solution (MCS game) reduced this negative effect

• Step-level and continuous public good games are not perfectly interchangeable– Differential effects of intervention– Perceived differently by players

Thank you