Current Zoology (Aug 2011)
Comparing children's Homo sapiens and chimpanzees' Pan troglodytes quantity judgments of sequentially presented sets of items
Abstract
We presented a quantity judgment task that involved comparing two sequentially presented sets of items to preschoolers and chimpanzees using nearly identical procedures that excluded verbal instructions to children. Trial difficulty in this task reflected the ratio difference between sets of discrete items where larger ratios (e.g., 0.80 as from comparing 4 to 5) were more difficult than smaller ones (e.g., 0.50 as from comparing 4 to 8). Children also completed verbal-based tasks probing the relationship between counting proficiency and performance on the quantity judgment task of sequentially presented identical sized items. Both species’ performance was best when ratios between comparison sets were small regardless of set size in all types of tasks. Generally, chimpanzees and older children performed better than younger children except at larger ratios. Children’s counting proficiency was not related to success in choosing the larger of two quantities of identical-sized items. These results indicate that chimpanzees and children share an approximate number sense that is reflected through analog magnitude estimation when comparing quantities [Current Zoology 57 (4): 419–428, 2011].
