1. COEVOLUTION of COOPERATION and SELECTIVE INTERACTION －AN EXPERIMENT－
Jun Kobayashi
Today is the FIRST day in Europe.
(in each slide)
Title → SUMMARY → read out → MOVE.
Jun Kobayashi (U of Chicago)
Hirokuni Ooura (Teikyo U)
Hideki Ishihara (Waseda U)
February 16, 2003
Cancun, SUNBELT

2. Jun Kobayashi (jun.kobayashi@uchicago.edu)
PLAN
QUESTION
THEORY
HYPOTHESES
METHOD
BUSINESS GAME
RESULT
CONCLUSION

3. Jun Kobayashi (jun.kobayashi@uchicago.edu)
QUESTION
MODERN SOCIETIES…
Can CHANGE PARTNERS.
Divorce, Move, Change Job, Multinational Firms, Immigrate.
COOPERATION in Dilemmas…
when CHANGE PARTNERS?
My basic interest is in problems of SOCIAL CHOICE.

4. Jun Kobayashi (jun.kobayashi@uchicago.edu)
PRISONERS' DILEMMA
Rational to DEFECT,
Worse than ALL COOPERATE.
Payoff
My basic interest is in problems of SOCIAL CHOICE.
Defection
Cooperation
# Cooperators

5. Jun Kobayashi (jun.kobayashi@uchicago.edu)
LITERATURE
COGNITIVE Solution…
COMMON VALUE (Sen).
STRUCTURAL Solution…
SANCTIONS (Olson).
STRATEGIC Solution…
TIT-FOR-TAT (Axelrod)
 LEAST Assumption.
My basic interest is in problems of SOCIAL CHOICE.

6. Jun Kobayashi (jun.kobayashi@uchicago.edu)
THEORY
SELECTIVE INTERACTION
(Dawes),
EXITING (Hayashi).
EXIT Cooperators' NETWORK.
BUT, NONTRIVIAL…
b/c Defectors FOLLOW.
My basic interest is in problems of SOCIAL CHOICE. C C D D C D D C

7. Jun Kobayashi (jun.kobayashi@uchicago.edu)
HYPOTHESES
"EXITING TIT-for-TAT'…
TIT-for-TAT in a Group,
EXIT when DEFECTED,
Cooperate in NEW Group. H1
SOME play "EXITING TFT." H2
Earn MORE than DEFECTORS.
My basic interest is in problems of SOCIAL CHOICE.

8. Jun Kobayashi (jun.kobayashi@uchicago.edu)
METHOD
Web-based EXPERIMENT.
Repeat PD Game in a GROUP,
MOVE to ANOTHER Group,
ANONYMOUS.
15-20 Subjects (students).
30-40 PD Games; 3-6 Moves.
6 Sessions, 111 Subjects.
2 Universities in Japan.
My basic interest is in problems of SOCIAL CHOICE.

9. Jun Kobayashi (jun.kobayashi@uchicago.edu)
My basic interest is in problems of SOCIAL CHOICE.

10. Jun Kobayashi (jun.kobayashi@uchicago.edu)
BUSINESS GAME
Work at one of 4 FIRMS.
If D (Work LAZILY), PAYOFF…
# Cooperators
# Workers in Firm
If C (Work HARD), PAYOFF…
D's Payoff － 2.
My basic interest is in problems of SOCIAL CHOICE.
Defection
Payoff
Cooperation
# Cooperators

11. Jun Kobayashi (jun.kobayashi@uchicago.edu)
EACH MONTH
Your CHOICE, PAYOFF
Each FIRM's PAYOFF
#Workers
My basic interest is in problems of SOCIAL CHOICE.
HOW to WORK?

12. Jun Kobayashi (jun.kobayashi@uchicago.edu)
EVERY 6 MONTHS
History of Each FIRM's PAYOFF,
#Workers
Each FIRM's AVERAGE PAYOFF
My basic interest is in problems of SOCIAL CHOICE.
WHERE to WORK?

13. Jun Kobayashi (jun.kobayashi@uchicago.edu)
RESULT
Mean SD C
.40
.24
Move
.54
Payoff
.80
.38
6 Sessions
111 Subjects
My basic interest is in problems of SOCIAL CHOICE.

14. Jun Kobayashi (jun.kobayashi@uchicago.edu)
DISTRIBUTION
move
behav.
EXIT
FIXED
RANDOM
total
TFT 30 10 8 48
All C 1 4 6
All D 7 3 2 12 5 27
Other 18 58 35
111
X2=8.89, p=0.36.
My basic interest is in problems of SOCIAL CHOICE.

15. Jun Kobayashi (jun.kobayashi@uchicago.edu)
TEST HYPOTHESIS 1
SOME play "EXITING TFT"?
SUPPORTED!
INDEPENDENCE b/w
BEHAVIOR / MOVE Strategies.
27%
(30 in 111)
My basic interest is in problems of SOCIAL CHOICE.

16. Jun Kobayashi (jun.kobayashi@uchicago.edu)
PAYOFF
move
behav.
EXIT
FIXED
RANDOM
total
TFT
0.77
0.90
0.80
All C
0.09
0.66
1.01
0.62
All D
0.91
0.87
1.39
0.98
0.83
0.68
0.88
0.79
Other
0.74
0.25
0.84
My basic interest is in problems of SOCIAL CHOICE.

17. Jun Kobayashi (jun.kobayashi@uchicago.edu)
TEST HYPOTHESIS 2
Exiting TFT BETTER than D?
DENIED!!
(p=0.06, one-side test).
B/c Defectors INVADE.
payoff 1
My basic interest is in problems of SOCIAL CHOICE.
0.9
ALL D
0.8
EXITING TFT
0.7
0.6
0.5
0.4
0.3
0.2
0.1 1 2
0.76
0.98

18. Jun Kobayashi (jun.kobayashi@uchicago.edu)
CONCLUSION
Possibility of COEVOLUTION,
BUT Needs MORE.
To Exclude Defectors,
DISTINGUISH Individuals.
EMERGENCE of Networks?
My basic interest is in problems of SOCIAL CHOICE.