Do long-tailed macaques engage in intuitive statistics?

Abstract

Phone +49 551 3851-0 2 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.3

Do infants and preschoolers quantify probabilities based on proportions?

“…which cup they tried to reach for), whereas the lollipop study [4] measured children's decision in terms of the cup towards which children moved. In the present study, in line with previous studies on non-human primates [8][9][10][11][12], we chose a reaching task because it was difficult for parents wearing opaque glasses to hold their royalsocietypublishing.org/journal/rsos R. Soc. Open Sci.…”

“…One could wonder why young children might fail at tasks at which other non-human animals seem to succeed. Non-human great apes [8][9][10], capuchin monkeys [11], one long-tailed macaque [12] and keas [13] were reported to succeed in tasks in which they had to make probability estimations and decisions based on proportions. Possibly, the methods used in these comparative studies were more suitable to uncover competence in non-human animals than in human children, i.e.…”

“…In previous studies, non-human animals could have based their inferences on the absolute number of preferred items that were visible (which we discussed in the Introduction), rather than on the proportions of preferred items, especially given that these items were food, which is a highly salient stimulus that might deflect reasoning in decisionmaking tasks [19][20][21]. This alternative strategy has only been explored in one study with long-tailed macaques [12] and could only be eliminated for one individual. Subjects could also have relied on a combination of heuristics, a strategy that children up to 10 years of age seem to use when tested with populations containing fewer elements [22].…”

“…The findings of the infant study encouraged a series of comparative studies with other animals [8][9][10][11][12][13]. These studies are important to better apprehend the distribution of probabilistic reasoning skills and come to a better understanding of their evolution.…”

Long-tailed macaques ( Macaca fascicularis ) can use simple heuristics but fail at drawing statistical inferences from populations to samples

“…Supporting material has been uploaded as part of the electronic supplementary material. The datasets generated and analysed during the current study, as well as the R scripts used for the analyses, have been deposited with Dryad Digital Repository: ( ) [ 46 ].…”