Figure 1.

Evidence from three groups of animals for within-session changes in conditioned eyelid responses that reverse between sessions. Two groups of rabbits were trained with delay conditioning using an ISI of 500 ms (D500, n = 33) and 1000 ms (D1000, n = 18), and a third group was trained with trace conditioning using a 500 ms CS and a 500 ms trace interval for a total ISI of 1000 ms (T1000, n = 33). A, B, Ten daily training sessions reveal that at asymptotic levels of performance (here, days 6–10) there are within-session decreases in response likelihood (A) and increases in latency to onset (B). C, more subtle within-session decreases are shown in response magnitude, which is the average amplitude of the responses that met the criterion for a conditioned response (i.e., excluding nonconditioned responses). For all three response measures, the within-session changes reverse between sessions.