Characteristics of the Retention of Color and Monochrome Images in Working Memory in the Monkey Macaca Mulatta

Behavioral experiments were run to assess the ability of rhesus monkeys to retain visual objects differing in shape, color, or a combination of these features in working memory. Six male rhesus monkeys performed a delayed matching-to-sample task in which three geometric shapes from a set of stimuli served as samples. In the first series of experiments, these were different colored figures of different shapes; samples in the second series were circles of different colors and samples in the third series were monochrome images of a number of figures from the stimulus set. Use of both cues to retain objects in memory resulted in the best performance by the monkeys; animals generally performed better on the color-matching task than the shape-matching task. This result is inconsistent with data reported from a number of other studies, where similar experiments – but with only one sample for memorization – yielded the opposite trend. The reason for this difference may be a shift in the focus of attention from local features (figure outlines) to global features (color) for memorization of information in the conditions of greater load on working memory used in our study.