Summation and numerousness judgments of sequentially presented sets of items by chimpanzees (Pan troglodytes)
Publication Type: |
Journal Article |
Year of Publication: |
2001 |
Authors: |
M.J. Beran |
Publication/Journal: |
Journal of Comparative Psychology |
Keywords: |
chimpanzees, numbers, pan troglodytes, summation |
ISBN: |
0735-7036 |
Abstract:
Summation and numerousness judgments by 2 chimpanzees ( Pan troglodytes) were investigated when 2 quantities of M&Ms were presented sequentially, and the quantities were never viewed in their totality. Each M&M was visible only before placement in 1 of 2 cups. In Experiment 1, sets of 1 to 9 M&Ms were presented. In Experiment 2, the quantities in each cup were presented as 2 smaller sets (e.g., +2 vs. 4+1). In Experiment 3, the quantities were presented as 3 smaller sets (e.g., 2+2+3 vs. 3+4+1). In Experiment 4, an M&M was removed from 1 set before the chimpanzees’ selection. In Experiments 1 and 2, the chimpanzees selected the larger quantity on significantly more trials than would be predicted by chance. In Experiments 3 and 4, 1 chimpanzee performed at a level significantly better than chance. Therefore, chimpanzees mentally represent quantity and successfully combine and compare nonvisible, sequentially presented sets of items.