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J Comp Psychol. 2004 Mar;118(1):25-36.

Chimpanzees (Pan troglodytes) respond to nonvisible sets after one-by-one addition and removal of items.

Author information

1
Language Research Center, Georgia State University, Decatur, GA, USA. mjberan@yahoo.com

Abstract

Two chimpanzees (Pan troglodytes) made numerousness judgments of nonvisible sets of items. In Experiment 1, 1-10 items were dropped 1 at a time into an opaque cup, and then an additional 1-10 items were dropped 1 at a time into another opaque cup. The chimpanzees' performance levels were high and were more dependent on factors indicative of an analogue-magnitude mechanism for representation of set size than on an object file mechanism. In Experiment 2, a 3rd visible set was made available after the sequential presentation of the first 2 sets. The chimpanzees again performed at high levels in selecting the largest of the 3 sets. In Experiment 3, 1 of the 2 initially presented sets was reduced in number by the sequential removal of 1, 2, or 3 items. Both chimpanzees performed above chance levels for the removal of 1, but not more than 1, item.

PMID:
15008670
DOI:
10.1037/0735-7036.118.1.25
[Indexed for MEDLINE]

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