title: Spontaneous use of magnitude discrimination and ordination by the orangutan (Pongo pygmaeus).
abstract: The ability to discriminate quantity is descriptive of general cognitive ability. In this study, the authors presented 2 orangutans (Pongo pygmaeus) with a quantity judgment task. Each trial consisted of 2 choices, ranging from 1 to 6 food items in each. The orangutan chose 1 of the quantities, which was removed, and the remaining array was given as a reward. In contrast to chimpanzees previously tested on the same task (S. T. Boysen & G. G. Berntson, 1995; S. T. Boysen, G. G. Berntson, M. B. Hannan, & J. T. Cacioppo, 1996; S. T. Boysen, K. L. Mukobi, & G. G. Berntson, 1999), the orangutans optimized their performance. Orangutans, therefore, attend to differences in magnitude and can spontaneously use ordinality. Results also suggest a cognitive difference between chimpanzees and orangutans.
authors.affiliation: National Zoological Park, Smithonian Institution, Washington, DC 20008, USA. rshumake@gmu.edu
authors.forename: R W
authors.initials: RW
authors.lastname: Shumaker
authors.forename: A M
authors.initials: AM
authors.lastname: Palkovich
authors.forename: B B
authors.initials: BB
authors.lastname: Beck
authors.forename: G A
authors.initials: GA
authors.lastname: Guagnano
authors.forename: H
authors.initials: H
authors.lastname: Morowitz
mesh_terms: D000818:Animals; D001070:Appetitive Behavior; D001288:Attention; D004193:Discrimination Learning; D005260:Female; D008297:Male; D009042:Motivation; D011148:Pongo pygmaeus / Q000523:psychology*; D011340:Problem Solving