Animal Cognition

, Volume 8, Issue 4, pp 253–262 | Cite as

Expectations about numerical events in four lemur species (Eulemur fulvus, Eulemur mongoz, Lemur catta and Varecia rubra)

  • Laurie R. Santos
  • Jennifer L. Barnes
  • Neha Mahajan
Original Article


Although much is known about how some primates—in particular, monkeys and apes—represent and enumerate different numbers of objects, very little is known about the numerical abilities of prosimian primates. Here, we explore how four lemur species (Eulemur fulvus, E. mongoz, Lemur catta, and Varecia rubra) represent small numbers of objects. Specifically, we presented lemurs with three expectancy violation looking time experiments aimed at exploring their expectations about a simple 1+1 addition event. In these experiments, we presented subjects with displays in which two lemons were sequentially added behind an occluder and then measured subjects’ duration of looking to expected and unexpected outcomes. In experiment 1, subjects looked reliably longer at an unexpected outcome of only one object than at an expected outcome of two objects. Similarly, subjects in experiment 2 looked reliably longer at an unexpected outcome of three objects than at an expected outcome of two objects. In experiment 3, subjects looked reliably longer at an unexpected outcome of one object twice the size of the original than at an expected outcome of two objects of the original size. These results suggest that some prosimian primates understand the outcome of simple arithmetic operations. These results are discussed in light of similar findings in human infants and other adult primates.


Prosimians Lemurs Expectancy violation paradigm Number representation 



The authors would like to thank Courtney Glavis-Bloom, Shannon Kundey, Webb Phillips, and Mariko Yamaguchi for help in pilot work and Valerie Kuhlmeier for her help running these studies. The authors would also like to thank Elizabeth Brannon and Monica Hoffine for helpful comments on an earlier version of this manuscript. The authors are also indebted to Allan Wagner for his assistance in securing this field site—the Myakka City Lemur Reserve. We are grateful to the Board of Directors of the Lemur Conservation Foundation and the staff, Penelope Bodry-Sanders, Monica Hoffine, and Kate Chapman. This research was supported by generous summer grants from the Yale College Dean’s Research Fellowship Program to J.B. and N.M and the Ezra Stiles Linck Fellowship to N.M. This work was approved by the Lemur Conservation Foundation IACUC committee and conforms to federal guidelines for the use of animals in research


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Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  • Laurie R. Santos
    • 1
  • Jennifer L. Barnes
    • 1
  • Neha Mahajan
    • 1
  1. 1.Department of PsychologyYale UniversityNew HavenUSA

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