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Are animals as irrational as humans?


The European starling, more rational than it seems. (Photo author: Cynthia Schuck Paim)
Click here for a high resolution photograph.

Animals in the wild are constantly confronted with decisions where to nest, who to mate, where the best forage is. Mainstream models of choice in both economics and biology predict that preferences will be rational, or consistent across contexts, as a result of being motivated by self interest or, in the case of animals, reproductive success. Yet many studies report that when making decisions people often take shortcuts, using cognitive heuristics that may lead to economically irrational decisions, with similar claims now showing up in animal behavior studies.

In a new study, Cynthia Schuck-Paim, Lorena Pompilio, and Alex Kacelnik question whether irrational decisions have been correctly demonstrated in animals. The authors suggest that observed "breaches of rationality" may stem from differences in the physiological state of animals "unwittingly imposed" by experimental design rather than from real irrational decisions.

To test this, the researchers trained European starlings to choose between two rich food sources (called focal options) and one of two poorer "decoys" in different contexts. Schuck-Paim and collaborators show that introducing the decoys resulted in an "irrational" preference only when the decoys were allowed to have an effect on food intake, suggesting that the choice resulted from the birds' energetic state rather than from cognitive mechanisms of choice similar to those used to explain irrationality in human subjects.

Altogether, Schuck-Paim and co-authors argue, these results warn that studies appropriating ideas from other disciplines can introduce confounding effects. Researchers would do well to carefully examine the underlying causes of observed animal behaviors when testing ideas formulated in a nonbiological framework.


Citation: Schuck-Paim C, Pompilio L, Kacelnik A (2004) State-Dependent Decisions Cause Apparent Violations of Rationality in Animal Choice. PLoS Biol 2 (12): e402.

CONTACT: Alex Kacelnik
University of Oxford
South Parks Road
Oxford, UK OX13PS
44-1865-271-120 (fax)


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