Rational decisions by humans and animals in the real world are bound by limited time, knowledge, and cognitive capacities. To understand and research rational decision making under uncertainty, we have developed three key concepts: bounded rationality, ecological rationality, and social rationality.

Bounded rationality.
Humans and other animals must make inferences about unknown features of their world under constraints of limited time, knowledge, and computational capacities.
We do not conceive bounded rationality as optimization under constraints nor do we think of bounded rationality as the study of how people fail to meet normative ideals. Rather, bounded rationality is the key to understanding how people make decisions without utilities and probabilities.
Bounded rationality consists of simple step-by-step rules that function well under the constraints of limited search, knowledge, and time-whether an optimal procedure is available or not. Just as a mechanic will pull out specific wrenches, pliers, and gap gauges to maintain an engine rather than just hit everything with a hammer, different tasks require different specialized tools. The notion of a toolbox full of unique single-function devices lacks the beauty of Leibniz’s dream of a single all-purpose inferential power tool. Instead, it evokes the abilities of a craftsman, who can provide serviceable solutions to almost any problem with just what is at hand.

Ecological rationality.
Models of ecological rationality describe the structure and representation of information in actual environments and their match with mental strategies such as boundedly rational heuristics. To the degree that such a match exists, heuristics need not trade accuracy for speed and frugality: investing less effort can also improve accuracy.
The simultaneous focus on the mind and its environment, past and present, puts research on decision making under uncertainty into an evolutionary and ecological framework, a framework that is missing in most theories of reasoning, both descriptive and normative. In short, we study the adaption of mental and social strategies to real-world environments rather than compare human judgment t the laws of logic and probability theory.

Social rationality.
Social rationality is a variant of ecological rationality, for which the environment is social rather than physical or technical. Models of social rationality investigate the boundedly rational strategies that people use when interacting with others.
There is a variety of goals and heuristics unique to social interactions. That is, in addition to the goals that define ecological rationality – to make fast, frugal, and fairly accurate decisions – social rationality is concerned with goals, such as choosing an option that one can defend with argument or moral justification, or that can create a consensus. To a much greater extent than the cognitive focus of most research on bounded rationality, socially adaptive heuristics include emotions and social norms that can act as heuristic principles for decision making.

Contact persons

The following faculty members and associated researchers may be addressed to give advice on research project proposals in “Rationality”:

Lael Schooler, Ph.D. (e-mail)
Henry Brighton, Ph.D. (e-mail)
Professor Gerd Gigerenzer (e-mail)

Key publications on this topic:

Gigerenzer, G. (2010). Moral satisficing: Rethinking moral behavior as bounded. Topics in Cognitive Science, 2, 528–554.

Brandstätter, E., Gigerenzer, G., & Hertwig, R. (2006). The priority heuristic: Making choices without trade-offs. Psychological Review, 113, 409–432.

Gigerenzer, G., & Brighton, H. (2009). Homo heuristicus: Why biased minds make better inferences. Topics in Cognitive Science, 1, 107–143.

Gigerenzer, G., & Gaissmaier, W. (2011). Heuristic decision making. Annual Review of Psychology, 62. 451–82.

Katsikopoulos, K. V., Schooler, L. J., & Hertwig, R. (2010). The Robust Beauty of Ordinary Information. Psychological Review, 117, 1259–1266.

Kruglanski, A., & Gigerenzer, G. (in press). Intuitive and deliberate judgments are based on common principles. Psychological Review.

Luan, S., Schooler, L. J., & Gigerenzer, G. (in press). A Signal Detection Analysis of Fast-and-Frugal Trees. Psychological Review.

Marewski, J. N., & Schooler, L. J., (in press).  Cognitive Niches:  An Ecological Model of Strategy Selection.  Psychological Review.

Mata, R., Schooler, L.J., & Rieskamp, J. (2007). The Aging Decision Maker:Cognitive Aging and the Adaptive Selection of Decision Strategies. Psychology and Aging, 22, 796–810.

Pachur, T., Mata, R., & Schooler, L. J. (2009). Cognitive aging and the use of recognition in decision making. Psychology and Aging, 24, 901–915.

Schooler, L. J., & Hertwig, R. (2005). How forgetting aids heuristic inference. Psychological Review, 112, 610–628.