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Animals with septal or cingulate lesions were tested on an 8-sec. or .6-sec. differential reinforcement of low rate schedule of reinforcement. Results showed that timing efficiency of animals with septal lesions was reduced below control levels when they were required to suppress responding for 1.2 sec. or longer. When reinforcements were periodically withheld follow-, ing a correct timing response, rates for all subjects accelerated. The increase in rate was greatest for the animals with septal lesions when their base-line reinforcement rate was equal to that of the control animals. These findings are attributed to the aversive properties of contingent response suppression and of omission of reinforcement. Animals with cingulate lesions were no different than control animals. These results are discussed in relation to the performance of organized complex sequences of behavior.

In two separate experiments, the response rates of rats with septal lesions were compared with those of control rats when response-independent food was presented while subjects were responding on a differential-reinforcement-of-low-rate schedule of reinforcement (Experiment 1) or according to a conjunctive differential-reinforcement-of-high-rate, fixed-ratio schedule (Experiment 2). Free-food deliveries resulted in acceleration of responding of subjects working on the low-rate schedule and in suppression of responding of those animals working on the high-rate schedule. Both of these effects were localized to a brief time period immediately following the free-food deliveries, and baseline rates of responding were not altered. The acceleration and suppression of responding that occurred on the respective schedules were greatly enhanced in rats with septal lesions. This finding supports the suggestion that these animals are hyperreactive to the reinforcing and/or eliciting properties of discrete stimulus events.