Chimpanzees (Pan troglodytes) respond to nonvisible sets after one-by-one addition and removal of items.
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.
Language Research Center, Georgia State University, Decatur, GA, USA. mjberan@yahoo.com
Michael J
MJ
Beran
D000818:Animals; D001522:Behavior, Animal; D003071:Cognition; D005260:Female; D007600:Judgment; D008297:Male; D008433:Mathematics; D002679:Pan troglodytes; D011930:Reaction Time; D013997:Time Factors; D014796:Visual Perception