Figure 2.

Relative impact of 900–4,500 shocks, given in a fixed (FT) or variable (VT) manner, on instrumental learning. Spinally transected rats received 900 FT or VT shocks, 4,500 FT or VT shocks, or no shock. Instrumental learning was then tested for 30 min. Subjects that received no shock or FT shock exhibited a progressive increase in response duration indicative of learning. Subjects that received 900–4,500 VT shocks failed to learn. The top panel depicts the design of the experiment. Performance over the 30 min test period is illustrated in the left panel and mean performance is depicted to the right. The error bars depict the ± SEM.