Chimpanzees demonstrate individual differences in social information use

Stuart K Watson,Lara A Wood,Rachel L Kendal,Susan P Lambeth,Lydia M Hopper,Lewis G Dean,Elizabeth E Price,Gillian L Vale,Andrew Whiten,Steven J Schapiro,Sarah J Davis

doi:10.1007/s10071-018-1198-7

Abstract

Studies of transmission biases in social learning have greatly informed our understanding of how behaviour patterns may diffuse through animal populations, yet within-species inter-individual variation in social information use has received little attention and remains poorly understood. We have addressed this question by examining individual performances across multiple experiments with the same population of primates. We compiled a dataset spanning 16 social learning studies (26 experimental conditions) carried out at the same study site over a 12-year period, incorporating a total of 167 chimpanzees. We applied a binary scoring system to code each participant’s performance in each study according to whether they demonstrated evidence of using social information from conspecifics to solve the experimental task or not (Social Information Score—‘SIS’). Bayesian binomial mixed effects models were then used to estimate the extent to which individual differences influenced SIS, together with any effects of sex, rearing history, age, prior involvement in research and task type on SIS. An estimate of repeatability found that approximately half of the variance in SIS was accounted for by individual identity, indicating that individual differences play a critical role in the social learning behaviour of chimpanzees. According to the model that best fit the data, females were, depending on their rearing history, 15–24% more likely to use social information to solve experimental tasks than males. However, there was no strong evidence of an effect of age or research experience, and pedigree records indicated that SIS was not a strongly heritable trait. Our study offers a novel, transferable method for the study of individual differences in social learning.

Highlights

Overzealous copying of one’s peers may lead to the adoption of sub-optimal or irrelevant behaviours (Giraldeau et al 2002; Kendal et al 2005)
This study used data collated from the same study site across 26 experimental conditions from 16 different studies of social learning, to explore whether sex, rearing history, age, prior research experience and genetic heritability had an important effect on chimpanzees’ proclivity for using social information from conspecifics to solve experimental problems
There was no evidence that age at the time of a study, nor the number of social learning studies an individual had participated in prior to a given study had a strong effect on Social Information Score (SIS)

Summary

Introduction

Overzealous copying of one’s peers may lead to the adoption of sub-optimal (e.g. an inefficient foraging method) or irrelevant behaviours (e.g. a male copying a female courtship gesture) (Giraldeau et al 2002; Kendal et al 2005). National Center for Chimpanzee Care in Texas is one such site, where 16 experimental studies (one unpublished) have investigated social learning over a 12-year period (Davis et al 2016; Dean et al 2012; Hopper et al 2007, 2008, 2012, 2015; Kendal et al 2015; Price et al 2009; Vale et al 2014, 2017c; Watson et al 2017a, 2018; Whiten et al 2007; Wood 2013, thesis available at http://www.etheses.dur.ac.uk/7274) We collated these data to investigate whether chimpanzees demonstrate individual differences in their propensity for using social information from conspecifics to solve experimental problems and if so, which characteristics may covary with this propensity. We explored whether the number of social learning studies in which individuals had participated influenced the likelihood that they would use social information in the study

Methods

Results

Discussion

Compliance with ethical standards