How does stone-tool use emerge? Introduction of stones and nuts to na�ve chimpanzees in captivity

Abstract

Nut-cracking behavior has been reported in several communities in West Africa but not in East and Central Africa. Furthermore, even within nut-cracking communities, there are individuals who do not acquire the skill. The present study aimed to clarify the cognitive capability required for nut-cracking behavior and the process through which the the nut-cracking behavior emerges. To examine emergence, we provided three naive adult chimpanzees with a single opportunity to observe human models. A human tester demonstrated nut-cracking behavior using a pair of stones and then supplied stones and nuts to the chimpanzee subjects. Two out of three chimpanzees proceeded to hit a nut on an anvil stone using a hammer stone, one of whom succeeded in cracking open the nuts during the first test session. The third chimpanzee failed to crack open nuts. We used four variables (object, location, body part used, and action) to describe stone/nut manipulation in order to analyze further the patterns of object manipulation exhibited by the subjects. The analysis revealed that there were three main difficulties associated with nut-cracking behavior. (1) The chimpanzee who failed at the task never showed hitting action. (2) The chimpanzee who failed at the task manipulated nuts but rarely stones. (3) The combination of three objects was not commonly observed in the three chimpanzees. We also discuss our results with reference to the effect of enculturation in captivity and the social context of learning in the wild.

Experimental studies illuminate the cultural transmission of percussive technologies inHomoandPan

“…Similarly, Hayashi et al [32] reported that already on the first day of observing a human cracking macadamia nuts, two of three human-reared chimpanzees placed a nut on an anvil stone and hammered it, with one succeeding on that day and the second on the next session. This is again consistent with social learning, yet there was no baseline or other control condition reported, weakening the strength of the evidence.…”

Investigating children as cultural magnets: do young children transmit redundant information along diffusion chains?

“…Understanding how we learn from others has been of interest to psychologists for over a century (Baldwin 1902;Rogers & Williams 2006), and during this time it has been investigated by a range of disciplines including anthropology, cognitive neuroscience, robotics and philosophy, as well as developmental, social and comparative psychology ( Dautenhahn & Nehaniv 2002;Meltzoff & Prinz 2002;Want & Harris 2002;Frith & Wolpert 2003;Bekkering et al 2005;Breazeal et al 2005;Hayashi et al 2005;Hurley & Chater 2005;Kubota 2005;Lukowski et al 2005). Research into children's social learning is undergoing a major expansion, stimulated in part by the integration of developmental and comparative perspectives ( Want & Harris 2002;Call et al 2005;Carpenter et al 2005;Tomasello et al 2005;Horner et al 2006;Tennie et al 2006;McGuigan et al 2007), which has allowed the distinction of social learning processes from the simple, such as local or stimulus enhancement, to the complex, including imitation and goal emulation.…”

Preliminary Assessment of Methods Used to Demonstrate Nut-Cracking Behavior to Five Captive Chimpanzees (Pan troglodytes)

“…Captive studies have similarly shown the effectiveness of a skilled demonstrator, whether it be a human model [Sumita et al, 1985;Hayashi et al, 2005;Hirata et al, 2009] or a proficient conspecific [Sumita et al, 1985;Marshall-Pescini and Whiten, 2008;Hirata et al, 2009]. Additionally, interindividual variation in acquisition of these skills that is present in wild populations is evident among captive chimpanzees as well.…”

“…In order to succeed at cracking nuts, individuals must be able to order objects hierarchically in both space and time [Matsuzawa, 1996], inhibit their focus towards food in order to find and combine tools [Sumita et al, 1985;Hayashi et al, 2005], understand the force necessary to break open a nut, and understand the size and weight differences needed for one tool to be a hammer and another an anvil [Bril et al, 2009]. In the wild, nut cracking is variable between cultural groups as well as individuals [Matsuzawa, 1994;McGrew et al, 1997;Hayashi et al, 2005]. Chimpanzees in separate communities crack distinct species of nuts and use different materials for anvils, even though the same nuts and tools are available to both communities.…”