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
Mean Giving per Trial
Giving by Trial Block
Control
Game:
Cheap
Continuous
Control
Cheap
Min Set
Mean giving per Trial
Block 3 Giving
Game:
Continuous
Min Set
Mean Giving/Pledge per Trial
Giving and Pledges by Trial Block
Pledge
Game:
Give
Continuous
Pledge
Give
Min Set
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