Fig. 2.

Diffusion chains starting with a model performing either the lift (Left) or slide (Right) method. The ID code of each chimpanzee is in bold (GG is the initial model performing lift; ER is the initial model performing slide). Dark shaded areas represent the percentage of door opening that involved lift, first when tested solo (T) and later when in the role of model (M) for the next, naïve, chimpanzee in the chain. Dark hatched areas represent the percentage of a model's lift actions watched by the naïve chimpanzee, and light hatched areas represent the same for slide actions. Dashed arrows indicate each individual's progression from the “T” (test) phase to the “M” (model) phase. Filled arrows mark pairings of each competent model with the naïve chimpanzee that followed them in the chain. Individuals excluded from chains were BO (did not observe the model), RN (failed model motivation check), AM (was not efficient at the task and withdrew), and CY (was aggressive toward the observer).