Study of intellectual activity at recognition of numerical multitudes of two-dimensional and three-dimensional stimuli of different color in lower monkeys

Abstract

The capability of monkeys for recognition and comparison by identity of two-dimensional images and three-dimensional objects of different color and number (from 1 to 5) was studied at solution of tasks of the “selection by sample” type. The study was carried out on two species of the lower monkeys of different levels of phylogenetic development: rhesus macaques (Macaca mulatta) and brown capuchins (Cebus apella). Representatives of the studied monkey species were established to able to differentiate two-dimensional stimuli (images of squares) and three-dimensional stimuli (objects of rounded shape) of red, yellow, and green color in different quantitative ratios (from 1 to 5) by selecting identical signs when solving modifications of the “selection by sample” tasks. The obtained data indicate the presence in primates of numerical notion and their ability to differentiate objects in the number from 1 to 5 regardless of the color of these objects. Speciesspecific differences in monkeys were revealed; rhesus macaques, as compared with capuchins, experienced difficulties at solution of complex combinatory tasks. The obtained experimental results give grounds to believe the presence in the lower monkeys the notion “quantity” as well as of the sufficiently high level of pre-verbal thinking.