Socially transmitted diffusion of a novel behavior from subordinate chimpanzees.
Chimpanzees (Pan troglodytes) demonstrate much cultural diversity in the wild, yet a majority of novel behaviors do not become group-wide traditions. Since many such novel behaviors are introduced by low-ranking individuals, a bias toward copying dominant individuals ("rank-bias") has been proposed as an explanation for their limited diffusion. Previous experimental work showed that chimpanzees (Pan troglodytes) preferentially copy dominant over low-rank models. We investigated whether low ranking individuals may nevertheless successfully seed a beneficial behavior as a tradition if there are no "competing" models. In each of four captive groups, either a single high-rank (HR, n = 2) or a low-rank (LR, n = 2) chimpanzee model was trained on one method of opening a two-action puzzle-box, before demonstrating the trained method in a group context. This was followed by 8 hr of group-wide, open-access to the puzzle-box. Successful manipulations and observers of each manipulation were recorded. Barnard's exact tests showed that individuals in the LR groups used the seeded method as their first-choice option at significantly above chance levels, whereas those in the HR groups did not. Furthermore, individuals in the LR condition used the seeded method on their first attempt significantly more often than those in the HR condition. A network-based diffusion analysis (NBDA) revealed that the best supported statistical models were those in which social transmission occurred only in groups with subordinate models. Finally, we report an innovation by a subordinate individual that built cumulatively on existing methods of opening the puzzle-box and was subsequently copied by a dominant observer. These findings illustrate that chimpanzees are motivated to copy rewarding novel behaviors that are demonstrated by subordinate individuals and that, in some cases, social transmission may be constrained by high-rank demonstrators.
Centre for Social Learning and Cognitive Evolution, and Scottish Primate Research Group, School of Psychology and Neuroscience, University of St Andrews, St Andrews, UK.
Stuart K
SK
Watson
National Centre for Chimpanzee Care, Michale E. Keeling Center for Comparative Medicine and Research, Department of Veterinary Sciences, UT MD Anderson Cancer Center, Bastrop, Texas.
Lisa A
LA
Reamer
National Centre for Chimpanzee Care, Michale E. Keeling Center for Comparative Medicine and Research, Department of Veterinary Sciences, UT MD Anderson Cancer Center, Bastrop, Texas.
Mary Catherine
MC
Mareno
Centre for Social Learning and Cognitive Evolution, and Scottish Primate Research Group, School of Psychology and Neuroscience, University of St Andrews, St Andrews, UK.|National Centre for Chimpanzee Care, Michale E. Keeling Center for Comparative Medicine and Research, Department of Veterinary Sciences, UT MD Anderson Cancer Center, Bastrop, Texas.
Gillian
G
Vale
Centre for Social Learning and Cognitive Evolution, and Scottish Primate Research Group, School of Psychology and Neuroscience, University of St Andrews, St Andrews, UK.
Rachel A
RA
Harrison
National Centre for Chimpanzee Care, Michale E. Keeling Center for Comparative Medicine and Research, Department of Veterinary Sciences, UT MD Anderson Cancer Center, Bastrop, Texas.
Susan P
SP
Lambeth
National Centre for Chimpanzee Care, Michale E. Keeling Center for Comparative Medicine and Research, Department of Veterinary Sciences, UT MD Anderson Cancer Center, Bastrop, Texas.|Department of Experimental Medicine, University of Copenhagen, Denmark.
Steven J
SJ
Schapiro
Centre for Social Learning and Cognitive Evolution, and Scottish Primate Research Group, School of Psychology and Neuroscience, University of St Andrews, St Andrews, UK.
Andrew
A
Whiten
D000818:Animals; D002755:Choice Behavior; D007858:Learning; D002679:Pan troglodytes; D012201:Reward; D012919:Social Behavior
chimpanzee; culture; dominance; rank; social learning