Variation in gaze-following between two Asian colobine monkeys
Gaze-following is a basic cognitive ability found in numerous primate and nonprimate species. However, little is known about this ability and its variation in colobine monkeys. We compared gaze-following of two Asian colobines—François’ langurs (Trachypithecus francoisi) and golden snub-nosed monkeys (Rhinopithecus roxellana). Although both species live in small polygynous family units, units of the latter form multilevel societies with up to hundreds of individuals. François’ langurs (N = 15) were less sensitive to the gaze of a human experimenter than were golden snub-nosed monkeys (N = 12). We then tested the two species using two classic inhibitory control tasks—the cylinder test and the A-not-B test. We found no difference between species in inhibitory control, which called into question the nonsocial explanation for François’ langur’s weaker sensitivity to human gaze. These findings are consistent with the social intelligence hypothesis, which predicted that golden snub-nosed monkeys would outperform François’ langurs in gaze-following because of the greater size and complexity of their social groups. Furthermore, our results underscore the need for more comparative studies of cognition in colobines, which should provide valuable opportunities to test hypotheses of cognitive evolution.
KeywordsGaze-following Inhibitory control François’ langurs Golden snub-nosed monkeys
This study was supported by the National Natural Science Foundation of China (Grant Nos. 31371040, 31571134, J1103602). We thank the François’ Langur Breeding Center in Wuzhou, Guangxi, China and the staff for their facilitation of the experiments. We also thank Ying Bi and Shuangxing Wang for their help with recoding the data. Thanks are due to Dr. Masaki Tomonaga for his technical advice on early versions of the manuscript. Thanks are also due to Meng Pei and Nelson Broche for their reading of the manuscript and valuable comments.
Compliance with ethical standards
Conflicts of interest
The authors declare no conflict of interest.
The authors declare that the study protocol was reviewed and approved by the Animal Care Committee of Peking University and the State Forestry Administration of China. All experiments conformed to the regulatory requirements of the breeding center.
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