Variance-sensitive choice in lemurs: constancy trumps quantity.


Journal Article

Numerous studies have demonstrated that animals' tolerance for risk when foraging can be affected by changes in metabolic state. Specifically, animals on a negative energy budget increase their preferences for risk, while animals on a positive energy budget are typically risk-averse. The malleability of these preferences may be evolutionarily advantageous, and important for maximizing chances of survival during brief periods of energetic stress. However, animals adapted to living in unpredictable conditions are unlikely to benefit from risk-seeking strategies, and instead are expected to reduce energetic demands while maintaining risk-aversion. We measured risk preferences in lemurs, a group of primates restricted to the island of Madagascar. Lemurs have evolved diverse anatomical and behavioral traits for survival in a harsh and unpredictable ecology, and these traits have been explained as forms of anatomical and behavioral risk reduction. We therefore predicted that lemurs would also be risk-averse in a behavioral task that offered subjects a choice between a small certain reward, and an uncertain but potentially large reward. In Experiment 1, the average rewards associated with the constant and variable options were equal and lemurs exhibited high levels of risk-aversion, replicating a phenomenon that has been demonstrated in dozens of taxa. In Experiment 2, we gradually increased the average value of the variable option relative to the constant option. Lemurs' preferences tracked these changes and subjects became more risk-seeking as the risk premium increased. However, many subjects maintained high levels of risk-aversion even when the average payout of the variable option yielded double that of the constant option. These results are consistent with the notion that lemur cognition has evolved to minimize risk in an unpredictable island environment.

Full Text

Cited Authors

  • MacLean, EL; Mandalaywala, TM; Brannon, EM

Published Date

  • January 2012

Published In

Volume / Issue

  • 15 / 1

Start / End Page

  • 15 - 25

PubMed ID

  • 21670948

Pubmed Central ID

  • 21670948

Electronic International Standard Serial Number (EISSN)

  • 1435-9456

International Standard Serial Number (ISSN)

  • 1435-9448

Digital Object Identifier (DOI)

  • 10.1007/s10071-011-0425-2


  • eng