Unique numerical competence of Asian elephants on the relative numerosity judgment task
Many animals demonstrate numerical competence even without language. However, their representation is mainly based on inaccurate quantity instead of absolute numbers. Thus, their performance on numerical tasks is affected by the distance, magnitude, and the ratio of comparisons (i.e., as distance decreases, magnitudes increase, or as ratios increase the accuracy of discrimination decreases). We report that Asian elephants’ numerical representation is quite different from that of other animals. We trained three Asian elephants to use a touch-panel apparatus and one female successfully learned to use the apparatus. Next, a relative numerosity judgment task was presented on the screen and the elephant was asked to touch, with the tip of her trunk, the figures with the larger numbers of items. The numbers of items in each figure ranged from 0 to 10. We found that her performance was unaffected by distance, magnitude, or the ratios of the presented numerosities but, consistent with observations of human counting, she required a longer time to respond to comparisons with smaller distances. This study provides the first experimental evidence that nonhuman animals have cognitive characteristics partially identical to human counting.
KeywordsNumerical competence Relative numerosity judgment Asian elephants
We would like to thank the Director and the elephant keepers at Ueno Zoo for their cooperation in this study.
This study was supported by the Japan Society for the Promotion of Science Grant-in-Aid for JSPS Fellows (22-6613) and ESB Cooperation Program in SOKENDAI (The Graduate University for Advanced Studies).
Compliance with ethical standards
Our study was approved by the Director of Ueno Zoo, after it was evaluated by the research and education committee at the zoo. Ueno Zoo is a member of the Japanese Association of Zoos and Aquariums (http://www.jaza.jp/index.html), which also has an animal welfare committee to confirm that Ueno Zoo meets their animal welfare standards as well. Since it was approved by the zoo, the current study meets the animal welfare standards of Japan.
Conflict of interest
The authors declare that they have no conflicts of interest.
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