Relative numerousness judgments by squirrel monkeys

Abstract

With nonnumerousness dimensions (e.g., pattern, area) controlled, three cards with two to seven black-filled circles were presented on each trial. If the center of three conditional cue lights was illuminated, the monkey was reinforced for selecting the card with the fewest circles; if two lights were on, the card with the intermediate number of circles was correct; and if three lights were on, the card with the most circles was correct. Training began with one conditional cue light and proceeded to the three-light condition. Then the one- and three-light conditions were presented randomly and concurrently, followed by the two-light condition. Finally, one, two, or three lights were presented randomly and concurrently. Only one monkey met criterion on all training stages, but another monkey succeeded also through the intermediate-number condition. It was concluded that the squirrel monkey is capable of relative numerousness judgments, including ordinal numerousness judgments. Additional discussion was concerned with the hypothesis suggested by Brown, Lenneberg, and Ettlinger (1978) that the ability to use quantitative concepts is a prerequisite to the acquisition of language. © 1980, The Psychonomic Society, Inc.. All rights reserved.