Rhesus Monkeys Have a Counting Ability and Can Count from One to Six.

Weiming Sun,Chaolin Ma,Baoming Li

doi:10.3390/brainsci11081011

Abstract

Counting ability is one of the many aspects of animal cognition and has enjoyed great interest over the last couple of decades. The impetus for studying counting ability in nonhuman animals has likely come from more than a general interest in animal cognition, as the analysis of animal abilities amplifies our understanding of human cognition. In addition, a model animal with the ability to count could be used to replace human subjects in related studies. Here we designed a behavioral paradigm to train rhesus monkeys to count 1-to-6 visual patterns presented sequentially with long and irregular interpattern intervals on a touch screen. The monkeys were required to make a response to the sixth pattern exclusively, inhibiting response to any patterns appearing at other ordinal positions. All stimulus patterns were of the same size, color, location, and shape to prevent monkeys making the right choice due to non-number physical cues. In the long delay period, the monkey had to enumerate how many patterns had been presented sequentially and had to remember in which ordinal position the current pattern was located. Otherwise, it was impossible for them to know which pattern was the target one. The results show that all three monkeys learned to correctly choose the sixth pattern within 3 months. This study provides convincing behavioral evidence that rhesus monkeys may have the capacity to count.

Highlights

IntroductionNumerical competence refers to the capacity of animals to recognize and name the cardinal numbers correlated with varying amounts of items and to order these numerals in the correct way [1]
Our results show that all three monkeys learned the 1-to-6 counting task; they knew to make a response to the sixth pattern exclusively, inhibiting responses to any patterns appearing at other ordinal positions
We may draw a conclusion that monkeys have a counting ability and can count from one to six

Summary

Introduction

Numerical competence refers to the capacity of animals to recognize and name the cardinal numbers correlated with varying amounts of items and to order these numerals in the correct way [1]. Davis and Perusse [2] expressed numerical competence as relative numerousness judgment, subtilizing, estimation, and counting. Subtilizing was elaborated and defined as the “immediate, correct assignation of number words to small collections of perceptual items”, emphasizing that it is basically a perceptual process, rather than a cognitive one [4]. Estimation was suggested to be the perceptual process underlying subtilizing when it applied to larger arrays of items. Estimation is considered to require considerable numerical sophistication, the assignment of a meaningful numerical tag to larger arrays of items may reflect only a perceptual process. A wide variety of animal species including birds [5,6], insects [7], rodents [8,9,10], dogs [11,12], fishes [13,14], and nonhuman primates [15,16,17,18] have shown some degree of numerical competence, as discussed above

Methods

Results

Conclusion