Cognitive differences between orang-utan species: a test of the cultural intelligence hypothesis.

A highly significant binomial GLMM (χ 2 ML = 33.24, N obs = 196, P < 0.0005; Table 1 ) revealed that, while controlling for the potentially confounding effects of age, sex, group size, the number of zoos a subject had lived in, and task identity, Sumatran subjects were significantly more likely to solve a task than their Bornean congeners (B = 1.934, SE = 0.74, z = 2.63, P < 0.01, Fig. 1 , Table 1 ).

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