Figure 4.

Memory for classical conditioning was heterogenous across species: Aplysia (diamonds), Dolabrifera (squares), Phyllaplysia (triangles). Mean reflex differential (Paired minus Unpaired, standardized by mean maximum for each species). Data are derived from the difference scores in Figures 1, 2, 3 to facilitate comparison. See those figures to determine variation around each score. Dolabrifera and Phyllaplysia showed significant learning, but only 15 min after training. Aplysia also showed significant learning averaged over all four post-tests. Symbols indicate statistical difference from pre-training baseline (two-tailed probabilities: +P ≤ 0.10; **P ≤ 0.01) using a repeated measures t-test with Bonferroni correction.