Macaque monkeys exhibit behavioral signs of metamemory in an oculomotor working memory task

The ability to monitor one's own memory processes is an important feature of human cognition and is referred to as metamemory. Although several human neuropsychological and neuroimaging studies have been conducted on metamemory, the neural mechanism that underlies this cognitive function is still unknown due to a lack of neurobiological research using nonhuman animals. In the present study, we trained four macaque monkeys to perform an oculomotor working memory task that was designed to be suitable for various neurobiological approaches to metamemory. In this task, the monkeys were sometimes allowed to choose to either take or escape from a spatial working memory test (Choice condition) and sometimes forced to take the test (Test condition). The difficulty of the task was manipulated by varying the number of distractors. We used two criteria to determine whether the monkeys showed metamnemonic ability: (1) there should be a negative correlation between memory performance in the Test condition and the escape rate in the Choice condition, and (2) memory performance should be better in the Choice condition than in the Test condition. Three of the four monkeys fulfilled these criteria. In addition, the response times of one of these three monkeys provided additional evidence that it used metamnemonic ability. These results suggest that the present task can be a useful tool for investigating the neural mechanism of metamemory in monkeys. Neurobiological research on metamemory using primate models is necessary to understand human cognition, and our study contributes to progress in this research area.