Observational learning in chimpanzees and children studied through 'ghost' conditions

Abstract

Emulation has been distinguished from imitation as a form of observational learning because it focuses not on the model's actions but on the action's environmental results. Whether a species emulates, imitates or displays only simpler observational learning is expected to have profound implications for its capacity for cultural transmission. Chimpanzees' observational learning has been suggested to be primarily emulative, but this is an inference largely based upon low fidelity copying in experiments when comparing chimpanzees with humans rather than direct testing. Here we test directly for emulation learning by chimpanzees and children using a 'ghost' condition in which a sliding door obscuring a reward was moved to left or right with no agent visible, a context associated with the only published evidence for emulation learning in a non-human species (pigeons). Both children and chimpanzees matched the observed direction of ghost door movement on their first test trial. This is the first evidence for emulation in a non-human primate in the restricted context of a ghost condition. However, only the children continued to match in later trials. Individuals of both species continued to match with 99% or better fidelity when viewing a conspecific model operates the door. We conclude that chimpanzees can and will display emulation learning when the task is as simple as the present one, which contrasts with a failure to do so in a more complex manipulative task tested earlier. However, even with a simple task, emulation alone creates only fleeting fidelity compared with the opportunity to copy a conspecific, when considerable conformity is displayed.

Figure 1

The slide box apparatus. Here the door is slid to the left, revealing the hole from which the reward can be retrieved. See text for further information.

Figure 2

Overall matching responses. Mean proportion of responses made by chimpanzees and children which matched the direction of the door movement demonstrated in the 20 min free-access period. Means and standard errors are shown to facilitate direct comparison with results for the pigeons tested by Klein & Zentall (2003). Standard errors for the latter were provided by the author (T. Zentall 2007, personal communication). Black bar, chimpanzees; light grey, children; dark grey bar, pigeons. Also, for comparison with the results of Klein, Zentall, one-sample t-test results for the chimpanzees and children are provided in the electronic supplementary material, appendix C.

Figure 3

Fluctuations in matching. Matching and non-matching pushes made during the free-access period by (a) chimpanzees ((i) push demo, (ii) enhanced ghost and (iii) ghost conditions) and (b) children ((i) push demo, (ii) enhanced ghost and (iii) ghost) in three conditions. Black, percentage of matching responses; grey, percentage of responses in the direction opposite to those demonstrated (n=58 for chimpanzees, n=15 for children).