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Decisions individualsQuè prediu la teoria i com es comporta la gent

Veurem

Decisions estratègiquesEl resultat ara depèn de les decisions teves i de les dels demés.

Què prediu la teoria i com es comporta la gent?

Què diu la teoria?

Anem a veure si es compleix.Anem a veure si es compleix.

Joc de cartes.Joc de cartes.

Si jugues la Si jugues la vermellavermella guanyes 2€. guanyes 2€.

Si jugues la Si jugues la negranegra no guanyes res però no guanyes res però l’altre guanya 3€.l’altre guanya 3€.

Negra Vermella

Negra (3,3) (0,5)

Vermella (5,0) (2,2)

Noves instruccions

Carta vermella, guanyes 2€.

Carta negra, l’altre guanya 8€.

Negra Vermella

Negra (8,8) (0,10)

Vermella (10,0) (2,2)

Conflicte

Entre incentius (socials) de cooperar i incentius (privats) de buscar l’interès propi

Machiavellli stresses civic virtues. Civic traditions of cooperation and trust (exemple de Napols). Adam Smith, lucre personal com a motor de l’economia (Wealth of Nations), virtuts cíviques com a motor de l’economia (Theory of Moral Sentiments). Tocqueville (Democracy in America). Putnam “Making democracy work” (1993), “Bowling alone” (2002) (associations, credit, capital social: normes de reciprocitat i reticules de relacions civiques), Fukuyama Trust (1996) “Coopetition” Cooperació en la producció i competencia en el repartiment.

Conflicte

b>c>a>d

THEORY It is self-evident how an intelligent individual should behave:

1) One-shotDominant strategy is the non-efficient equilibrium (c>a)

2) Finite game Even with thousands of trials, not a single efficient equilibrium predicted.No convergence to infinitely-repeated game.

NC C

NC a,a b,d

C d,b c,c

• Equilibri subóptim. One-shot: away from 0 or 100% cooperation

• Què passaria si es repetís el joc entre els mateixos jugadors?

• I entre jugadors diferents?

• Què passa si s’anuncia el nombre de períodes que es juguen?

• What is an infinite game Fixed probability of finishing; it affects results: more cooperation when probability of continuing is larger.

Dilema de los presos, Andreoni, Miller, EJ 1993

Three experiments

Selten & Stoecker (1986)

25 supergames of 10 periods.In each supergame a pattern of cooperation, defect and defect all the way. In the experiment, the moment of defection moves earlier. In the last 5 supergames, no cooperation at all. Theory’s prediction is too extreme, but better approximation with practice.

Observation leads to a theory of learning and to new theories of decision making as in:

b. Kreps, Milgrom, Roberts and Wilson (1982) Rational behavior when you have doubts about rationality

of your opponent.

c. Andreoni & Miller (1993) Building a reputation. Reciprocal altruism (cooperate until experience shows

that they are taking advantage...). Pure altruism (taking pleasure in others pleasure).

And one set of simulations :Axelrod, The Evolution of Cooperation (1984)

Computer tournaments

a. on a 200-play repeated PD.

b. P=.99 of continuing (only the first half of entries and Tit for Tat would have been 4th after 25, 16 and 8.

Variations:-Letting subjects talk to each other-Letting subjects choose their partners-Letting them know each other in a local interaction

Field centipedeField centipede