Animal Cognition

, 14:695 | Cite as

Relative quantity judgments in South American sea lions (Otaria flavescens)

  • José Z. AbramsonEmail author
  • Victoria Hernández-LloredaEmail author
  • Josep Call
  • Fernando Colmenares
Original Paper


There is accumulating evidence that a variety of species possess quantitative abilities although their cognitive substrate is still unclear. This study is the first to investigate whether sea lions (Otaria flavescens), in the absence of training, are able to assess and select the larger of two sets of quantities. In Experiment 1, the two sets of quantities were presented simultaneously as whole sets, that is, the subjects could compare them directly. In Experiment 2, the two sets of quantities were presented item-by-item, and the totality of items was never visually available at the time of choice. For each type of presentation, we analysed the effect of the ratio between quantities, the difference between quantities and the total number of items presented. The results showed that (1) sea lions can make relative quantity judgments successfully and (2) there is a predominant influence of the ratio between quantities on the subjects’ performance. The latter supports the idea that an analogue representational mechanism is responsible for sea lions’ relative quantities judgments. These findings are consistent with previous reports of relative quantities judgments in other species such as monkeys and apes and suggest that sea lions might share a similar mechanism to compare and represent quantities.


Numerical cognition Relative quantity judgment Sea lion Comparative cognition Accumulator model 



We are grateful to the directors of the L’Oceanografic aquarium of Valencia and Zoo Aquarium of Madrid for allowing us to conduct this research. Special thanks go to Miguel Bueno Brinkman and Manuel Castellote for their help and support and to José Antonio Esteban for help with video recordings and for providing very helpful ideas that contributed to the design of this study. We appreciate the work of the animal keepers from the two aquariums. From L’Oceanografic aquarium of Valencia, head coach Victor Sánchez, for sea lions training and management and the trainers team; Jerome Coello, Javier Escudero, Ana Coba, Luciana Suárez and Sandra Salido. Zoo Aquarium of Madrid head coach Carlos de las Parras for sea lions training and management and the trainers team; Arancha Sánchez, Cacha Martínez, Berta Romeral, Pablo Juárez, Pablo Roy, Antonio Martínez, Irene Ayllon and Craig Allum. In addition, we thank Luis Franco for his enormous help in the design and manufacturing of the apparatus used in this study. Thanks to Rosario Martínez Arias and Ma José Hernández-Lloreda for their comments and statistical advice. Special thanks go to Titaví for her artwork. Research reported in this study was partly supported by FPI studentship to José Francisco Zamorano Abramson, and project grants CCG08-UCM/SAL-4007 (Universidad Complutense de Madrid y Comunidad de Madrid) to M. V. Hernández-Lloreda, and UCM-BSCH GR58/08 (Universidad Complutense de Madrid y Banco Santander Central Hispano) and D/018712/08 AECID (Agencia Española de Cooperación Internacional y Desarrollo), Spain to F. Colmenares.

Conflict of interest

The authors declared that they had no conflicts of interests with respect to their authorship and/or the publication of this article.


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Copyright information

© Springer-Verlag 2011

Authors and Affiliations

  1. 1.Dpto. PsicobiologíaUniversidad Complutense de MadridMadridSpain
  2. 2.Dpto. Metodología de las Ciencias del ComportamientoUniversidad Complutense de MadridMadridSpain
  3. 3.Max Planck Institute for Evolutionary AnthropologyLeipzigGermany

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