how simple strategies can explain - philipp aerni · gigerenzer, hertwig, & pachur, 2011). the...

How simple strategies can explain ‘good’ and ‘bad’ behavior

Ralph Hertwig

Center for Adaptive Rationality (ARC)

A hero of an unprecedented kind

(Chateaubriand)

110 rules of civility and decent behavior

Rule 6.

Sleep not when others speak, sit not when others stand, speak not when you should hold your peace, walk not on when others stop.

Rule 100.

Cleanse not your teeth with the table cloth napkin, fork, or knife; but if others do it, let it be done without a peep to them.

Rule 69.

If two contend together, take not the part of either unconstrained, and be not obstinate in your own opinion. In things indifferent be of the major side.

I will argue …

Homo heuristicus Much of human decision making can be understood in terms of simple heuristics.

(NB: They often result in surprisingly accurate performance; see Gigerenzer, Hertwig, & Pachur, 2011).

The emergence of behavioral complexity The interaction of a simple heuristic with properties of the world can produce complex behavior, including moral inconsistencies.

Judging character (or lack thereof) Moral dispositions (e.g., virtuousness, fairness) or lack thereof can (often) not be inferred from behavior alone.

Rather, normative evaluations require the analysis of heuristic‒environment interactions (see Doris, 2002).

What heuristics are

• A heuristic is a strategy that neither searches, weighs, and adds up all available information, nor makes extensive use of computation to reach optimized solutions. – “Approximate methods” (Simon, 1990)

• Rule 69. …. In things indifferent be of the major side.

Gigerenzer, Hertwig, & Pachur (2011). Heuristics: The foundations of adaptive behavior. OUP.

Why heuristics are indispensable tools

• Computational intractability

No brain or existing machine can compute the optimal strategy (if it existed)

E.g., in chess Deep Blue would need 55 billion years to think 10 moves by each party ahead

• Competing, incommensurable reasons in social

environments

Sacred values preclude tradeoffs (Tetlock et al., 2000)

Hertwig, Hoffrage, & the ABC Research Group (2009). Simple heuristics in a social world. Oxford.

© Die Zeit

“I appointed Guttenberg as a defense minister. I did not

appoint him as a research assistant or doctoral student or

a holder of a degree. I am concerned with his work as a

defense minister, and he is accomplishing that

excellently. That is what counts for me.”

Why heuristics are indispensable tools

• Computational intractability

No brain or existing machine can compute the optimal strategy (if it existed)

E.g., in chess Deep Blue would need 55 billion years to think 10 moves by each party ahead

• Competing, incommensurable reasons in social

environments

Sacred values preclude tradeoffs (Tetlock et al., 2000)

• Time pressure

Hertwig, Hoffrage, & the ABC Research Group (2009). Simple heuristics in a social world. Oxford.

• Heuristics based on

– one-reason decision

making (e.g., fully

zipped, bulky coat)

– few cues: older,

female and single

The emergence of behavioral

complexity

The interaction of a simple heuristic with properties of the world can produce complex behavior, including moral inconsistencies.

Allocation patterns of parental time

Hertwig, Davis, & Sulloway (2002). Psychological Bulletin, 128, 728–745.


Sociological analysis. “As members of an egalitarian society, Americans typically espouse equal treatment of children by parents.” (Zervas & Sherman, 1994, p. 31)

Equity heuristic (1/N heuristic)

Divide resources (e.g., time, attention, money,

medicine, food) equally among your N children at any

given point in time.


Do parents use 1/N?

Price (2008). Journal of Human Resources, 43, 240–265.

Division of estate (last will)

More than two-thirds in U.S. divide their

estates equally among their children (Bernheim & Severinov, 2003, Journal of Political Economy)

Some assumptions

Parental investment period. Divided into a number of intervals of equal length.

1/N heuristic. Applied within each of these intervals.

Donor of resources. Only parents but not children donate resources.

Resource budget. Limited and stable.

• Interpersonal resources (e.g., time)

• Cognitive resources (e.g., intellectual stimulation)

• Material resources (e.g., health care, higher education fees)

1970‒74

1975‒79

1980‒84

1985‒89

1990‒94

1995‒99

Cumulative resources: U-shaped trend

Middle-born resource handicap

Judging character (or lack thereof)

Moral dispositions (e.g., virtuousness, fairness) or

lack thereof can (often) not be inferred from

behavior alone. Rather, normative evaluations

require the analysis of heuristic‒environment

interactions.

Micromotives and macrobehavior

Schelling (1971). Journal of Mathematical Sociology, 1, 143–186.

Conclusions

• People use simple heuristics to navigate complex, conflicting, uncertain and fast-changing environments.

• The heuristics’ behavioral outcomes—often used to infer “character”—depend often on their interaction with properties of the environment. But inferences about character underestimate the impact of the environment.

• Teach and practice simple rules (e.g., Washington).

• Change the environment (e.g., default heuristic and organ donation opt-out system; Johnson & Goldstein, 2003).

How simple strategies can explain ‘good’ and ‘bad’ behavior

Ralph Hertwig

Center for Adaptive Rationality (ARC)

Interbirth interval and inequality


• Evolutionary analysis. A unit of investment is divided equally unless its marginal benefit is larger for one child than for another. (Hamilton, 1964; Trivers, 1974)

• Economic analysis. If the parental payoff curve, which depends on child “quality” (e.g., abilities, health), is the same for each child, parents distribute equally among children. (Becker, 1991)

• Sociological analysis. “As members of an egalitarian society, Americans typically espouse equal treatment of children by parents.” (Zervas & Sherman, 1994, p. 31)

Possible solutions

Family size and inequality


The complex world of parental

investment

• Children are “gas guzzlers,” and parental resources are limited.

• In hunter–gatherer societies, a child consumes between 10 and 13 million calories more than s/he produces (age 0 to 18; Kaplan, 1994).

• How should parents allocate the myriad resources required (e.g., food, medicine, attention, love, and education)?

Coall & Hertwig (2010). Behavioral and Brain Sciences, 33, 1–19.

Tit-for-tat strategy

• Cooperate on the first move, and then do whatever the opponent has done on the previous move.

Tit-for-tat Always defect

Cooperate Defect

Defect Defect

Defect Defect

Defect Defect

Defect Defect

Tit-for-tat Always coop.

Cooperate Cooperate

Cooperate Cooperate

Cooperate Cooperate

Cooperate Cooperate

Cooperate Cooperate

Round

1

2

3

4

5

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