Chimpanzees copy dominant and knowledgeable individuals : implications for cultural diversity

RLK was funded by a Royal Society Dorothy Hodgkin Fellowship; LMH by a BBSRC studentship (BBS/S/K/2004/11255 supervised by AW) and, at the time of writing, is funded by the Guthman Fund; WH by a BBSRC grant (BB/I007997/1); SFB by a NSF CAREER award (SES 0847351) and (SES 0729244). The chimpanzee colony is supported by NIH U42 (RR-15090).Evolutionary theory predicts that natural selection will fashion cognitive biases to guide when, and from whom, individuals acquire social information, but the precise nature of these biases, especially in ecologically valid group contexts, remains unknown. We exposed four captive groups of chimpanzees (Pan troglodytes) to a novel extractive foraging device and, by fitting statistical models, isolated four simultaneously operating transmission biases. These include biases to copy (i) higher-ranking and (ii) expert individuals, and to copy others when (iii) uncertain or (iv) of low rank. High-ranking individuals were relatively un-strategic in their use of acquired knowledge, which, combined with the bias for others to observe them, may explain reports that high innovation rates (in juveniles and subordinates) do not generate a correspondingly high frequency of traditions in chimpanzees. Given the typically low rank of immigrants in chimpanzees, a 'copying dominants' bias may contribute to the observed maintenance of distinct cultural repertoires in neighboring communities despite sharing similar ecology and knowledgeable migrants. Thus, a copying dominants strategy may, as often proposed for conformist transmission, and perhaps in concert with it, restrict the accumulation of traditions within chimpanzee communities whilst maintaining cultural diversity.PostprintPeer reviewe