Fig. 4. N. pompilius expresses a bi-phasic memory curve. There was expression of two distinct memory peaks in animals conditioned with a light pulse plus food odour association (CS+, black bars; N=6) for both behaviours we measured: (A) tentacle extension response (TER), and (B) ventilation rate. The short-term memory peak was expressed at 3 and 30 min after training, whereas a long-term memory peak was apparent at 6 and 12 h after training, and persisted for less than 24 h. The control group (CS–, white bars; N=6) received a light pulse combined with home-tank water during training and showed little change in behaviour over the six test periods. Graphs show the mean ± 1 s.e.m. Asterisks above the bars denote a significant difference (P0.05) between CS+ and CS– measures at each time interval. The linking bars below the x-axis show significant differences (P0.05) within the CS+ group compared across test procedures at each retention interval. There were no significant differences in the CS– group across test periods.