Programme Level Social Learning in Great Apes : Cognitive and Welfare Perspectives.

Programme Level Social Learning (PLSL) was investigated in seven captive chimpanzees (Pan troglodytes) and 40 human infants (18-54 month old). Methodology was developed that allowed multiple behavioural levels and multiple indicators of hierarchical organisation to be assessed. A water tube task was used, were an outer tube was made watertight (by insertion of three plugs into three open sockets) and filled with water to float a food reward within reach. The chimpanzees and children showed no evidence of PLSL according to Byrne and Russon’s (1998) strict criteria, but they did demonstrate considerable social learning; they learned stages and subroutine units (children additionally learned behavioural details) but the order of stages, and subroutine orders were not copied. Differences between species were apparent regarding the social learning processes used. Children learned principally by imitation, chimpanzees learned via stimulus/local enhancement, emulation and possibly blind mimicry. Children also learned at four of the five behavioural levels investigated and older children completed the task. Chimpanzees learned only two intermediate-to-global behavioural levels, and no chimpanzee completed the task. Both the chimpanzees and children hierarchically organised their water-tube directed behaviour. The chimpanzees did not understand plug-use, they lacked experience of plugs and sockets, but may also have been unable to read the intentions of the demonstrator to waterproof the water tubes using the plugs. Chimpanzee intention-reading ability was tested but a lack of experience of the testing situation deterred the chimpanzees from participating; no intention-reading results were obtained. The assumption that chimpanzees benefit from participating in cognitive research was empirically investigated by considering changes in the concentration of faecal glucocorticoid metabolite (‘stress hormone’) and behaviour. The welfare of female participants showed significant improvement during the social learning experiment compared to baseline, whereas males became more stressed. Welfare must be considered in future social learning research. Previous experience influenced learning throughout