All three chimpanzees showed a highly significant preference for touching the POS cone first in all choice sessions (binomial tests: all p < 0.01), with all three animals showing perfect performance in at least two of the five sessions.
A general linear model on the latencies to touch NP, M and NN cones, with chimp, valence (continuous) and their interaction as predictors and speed as a continuous covariate, showed that these latencies differed between chimpanzees (effect of chimp: F (2, 116) = 15.52, p < 0.001); there was also a near-significant interaction between chimpanzee and valence (interaction of chimp × valence: F (2, 116) = 2.54, p = 0.083).