Relative numerousness judgment and summation in young, middle-aged, and older adult orangutans (Pongo pygmaeus abelii and Pongo pygmaeus pygmaeus)
Publication Type: |
Journal Article |
Year of Publication: |
2007 |
Authors: |
Ursula S. Anderson, Tara S. Stoinski, Mollie A. Bloomsmith, Terry L. Maple |
Publication/Journal: |
Journal of Comparative Psychology |
Keywords: |
age differences, cognition, ordinality, quantitative judgment |
ISBN: |
1939-2087 0735-7036 |
Abstract:
The ability to select the larger of two quantities ranging from 1 to 5 (relative numerousness judgment [RNJ[) and the ability to select the larger of two pairs of quantities with each pair ranging from 1 to 8 (summation) were evaluated in young, middle-aged, and older adult orangutans (7 Pongo pygmaeus abelii and 2 Pongo pygmaeus pygmaeus). Summation accuracy and RNJ were similar to those of previous reports in apes; however, the pattern of age-related differences with regard to these tasks was different from that previously reported in gorillas. Older orangutans were less accurate than the young and middle-aged for RNJ, and summation accuracy was equivalent among age groups. Evidence was found to suggest that the young and middle-aged based their selection of the largest quantity pair on both quantities within each pair during the summation task. These results show a relationship between subject age and the quantitative abilities of adult orangutans.