Two central nervous system stimulants, magnesium pemoline and dextroamphetamine, were tested to see if they facilitate learning in human subjects. Subjects under placebo learned faster than the subjects under any of the several doses of magnesium pemoline; however, none of these differences reached statistical significance. Subjects who received dextroamphetamine learned significantly more slowly than those who received placebo.

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The resistance to extinction of the positive stimulus in discrimination learning was evaluated in 2 experiments using rats and single stimulus presentation on an elevated runway. In Experiment I, discrimination groups received reinforcement to white and nonreinforcement to gray (WG) or black (WB). Reference groups received all trials to white under 100% (W+ and w+ which differ in number of trials) or 50% (W±) reinforcement. Both mean log speed of approach and parameter estimates from the extinction curves showed (Tukey tests) the extinction performance of the discrimination groups as more similar to W+ and w+ than to W±. Experiment II yielded comparable results for WG and WB for both the approach and an additional goal platform measure.