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.
Allocation patterns of parental time
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.
Hertwig, Davis, & Sulloway (2002). Psychological Bulletin, 128, 728–745.
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)
Allocation patterns of parental time
Hertwig, Davis, & Sulloway (2002). Psychological Bulletin, 128, 728–745.
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
Hertwig, Davis, & Sulloway (2002). Psychological Bulletin, 128, 728–745.
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.
Hertwig, Davis, & Sulloway (2002). Psychological Bulletin, 128, 728–745.
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
Hertwig, Davis, & Sulloway (2002). Psychological Bulletin, 128, 728–745.
• 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
Hertwig, Davis, & Sulloway (2002). Psychological Bulletin, 128, 728–745.
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.
Allocation patterns of parental time
Hertwig, Davis, & Sulloway (2002). Psychological Bulletin, 128, 728–745.
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
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