Rule Rationality vs. Act Rationality Robert Aumann

Rule Rationality vs. Act Rationality

• Robert Aumann

• The Center for Rationality

• The Hebrew University, Jerusalem

• The Fifth European Conference

• On Complex Systems

• Jerusalem, September 2008

a. Bees, flowers, and nectar

• (Andreas Bertch, circa 1985, unpublished)

• Q: Actually, why would you expect rationality

• from a bee?

• A: EVOLUTION – survival of the fittest

• (explain)

Rule Utilitarianism vs. Act Utilitarianism

• John Harsanyi
• John Stuart Mill
• Fyodor Dostoyevsky
• Jeremy Bentham

• In making ethical judgments, should one consider the RULE?

• (“Thou shalt not murder”)

• – or the ACT

• (“Is this murder justified?”)

• In either case, judgments are made on a UTILITARIAN basis

• (i.e., maximum welfare of society)

Rule Rationality vs. Act Rationality

• In making decisions, should one consider the RULE?

• (“Stick to what you’ve learned”)

• – or the ACT

• (“How do you get nectar?”)

• In either case, judgments are made on an EGOTISTIC basis

• (i.e., maximum individual welfare)

• In the Ultimatum Game:

• Should one consider the RULE?

• Don’t let people kick you in the stomach!

• – or the ACT

• Should I take DM 20 or nothing?

• Q: These are not ethical, philosophical issues.

• Why shouldn’t I just maximize my welfare?

• What’s the importance of the “RULE”?

• A: Rule Rationality is a POSITIVE notion,

• not a NORMATIVE one

• (unlike Rule Utilitarianism).

• Rationality is an expression of evolutionary forces, which work by the RULE, not the

• exception, not the contrived situation.

• BEES & FLOWERS

• ULTIMATUM GAME

• Nature develops mechanisms that are

• RULE RATIONAL

• Mechanisms

• BEES & FLOWERS

• Learning window

• ULTIMATUM GAME

• PRIDE, SELF-RESPECT,

• INSULT, REVENGE

Other Examples:

• Hunger & enjoyment of food

• Bees & orchids

• Enjoyment of sex

• Polls – giving the “right” answer (Yonatan)

• Camerer’s taxi drivers

• Arrow’s Pacific Island story

• Room temperature

• Probability matching

• – Choosing a route to get to work (Dreze)

• Repeated prisoner’s dilemma

• Recency

• Professor Selten’s Umbrella