Figure 3.

Timeline of the five consecutive phases of the study. The total number of sessions needed to reach the learning criterion varied between animals (noted x), for Colored Cards, x ≤ 18, for Images of faces x ≤ 15. The learning criterion (≥80% correct choices over two consecutive sessions, or ≥80% correct choices in two out of three consecutive sessions and ≥60% in the penultimate) was evaluated during the three last sessions of both the Colored Cards and the Image of faces phase, as indicated. Sessions framed by thick black lines were analyzed. During transition sessions, images of faces framed by the corresponding color (rewarded image = rewarded shade of green and vice versa) were presented. The final training sessions are noted S_x. H, habituation; S, training sessions; T, tests sessions; tr, transition sessions.