Fig. 2.

(A, left) Schematic representation of one trial. Trials always started with the presentation of a red circle: once the chimpanzee touched it, the sound triplet was played, the two visual sequences shown and chimpanzees’ latency to respond recorded. Boxplots of FK’s (B) and KL’s (C) latencies in providing the correct response. Median latencies across trials were significantly shorter (see main text and Table 1) in the isomorphic than in the non-isomorphic condition, namely 5.68 vs. 8.25 s (ape FK) and 8.52 vs. 14.27 s (KL).