Do long-tailed macaques engage in intuitive statistics?

Abstract

Human infants, apes and capuchins have been found to engage in intuitive statistics, generating predictions from populations to samples based on proportional information. This suggests that statistical reasoning might depend on some core knowledge that is shared with other species. Here, we investigated whether such intuitive statistical reasoning is also present in a species of Old World monkeys, to aid in the reconstruction of the evolution of this capacity. In a series of 7 test conditions, 11 long-tailed macaques were offered different pairs of populations containing varying proportions of preferred vs. neutral food items. One population always contained a higher proportion of preferred items than the other. An experimenter simultaneously drew one item out of each population, hid them in her fists and presented them to the monkey to choose. Results revealed that at least one individual seemed to make systematic population-to-sample inferences and consistently chose the sample from the population with the more favorable distribution of preferred vs. neutral food items. While it is not clear whether she used relative or absolute quantities of food, she seemed to understand the difference between a correct choice and a favorable draw and thus some basic principles of intuitive statistics.