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Two groups of turtles were given training on fixed ratio schedules of reinforcement. The first group was trained daily in 10 min. sessions but increases in ratio schedule were not made in unitary increments. The second group was trained with a two day interval between 30 min. training sessions with unitary increments in the ratio schedules. The performance of the groups was similar in that subjects in neither group showed a significant increase in response rate. The performance of the first, however, was sustained over higher ratio schedules before showing decreased response rates.

Two experiments were conducted to analyze the effects of scopolamine HBr and magnesium pemoline on spontaneous activity and water intake. Both drugs were found to increase the level of wheel running but with different temporal parameters. Water intake was increased by magnesium pemoline, whereas scopolamine decreased the amount of water consumed during the activity increase. Results are discussed with regard to the interpretation of drug effects on performance in appetitive and nonappetitive reward situations.

Six groups of six rats were run for 15-min daily sessions in an operant situation under either magnesium pemoline (MP) or saline Conditions. The design consisted of four days of acquisition followed by two days of extinction repeated four times. The results indicated that there was a slight tendency for MP to maintain more resistance to extinction as measured by response rate. The differential resistance is decreased by further acquisition-extinction sessions beyond the second set. The possible facilitating effects of MP are apparently reduced by the repeated exposure to the acquisition-extinction conditions.

Two turtles each were trained on variable interval, fixed interval, variable ratio, and fixed ratio schedules of reinforcement. Two additional turtles were run on fixed ratio schedules because the response rates could not be maintained. The remaining schedules produced levels of performance which were similar to each other with the variable ratio schedule appearing to be the most stable and effective.