title: Relative numerousness judgment and summation in young, middle-aged, and older adult orangutans (Pongo pygmaeus abelii and Pongo pygmaeus pygmaeus).
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.
authors.affiliation: School of Psychology, Georgia Institute of Technology, Atlanta, GA 30332-0170, USA. uanderson@zooatlanta.org
authors.forename: Ursula S
authors.initials: US
authors.lastname: Anderson
authors.forename: Tara S
authors.initials: TS
authors.lastname: Stoinski
authors.forename: Mollie A
authors.initials: MA
authors.lastname: Bloomsmith
authors.forename: Terry L
authors.initials: TL
authors.lastname: Maple
mesh_terms: D000375:Aging / Q000523:psychology*; D000818:Animals; D001076:Aptitude; D004193:Discrimination Learning; D005260:Female; D007600:Judgment; D008297:Male; D008433:Mathematics; D011148:Pongo pygmaeus / Q000523:psychology*; D011340:Problem Solving; D013045:Species Specificity