Melatonin: Effect on Punished and Nonpunished Operant Behavior of the Pigeon

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Science  26 Mar 1971:
Vol. 171, Issue 3977, pp. 1258-1260
DOI: 10.1126/science.171.3977.1258


Intramuscular injections of melatonin had a dose-dependent, rate-increasing effect on responding maintained by a fixed-interval schedule of positive reinforcement. When a punishment contingency was added to the fixed-interval schedule, the overall rates were not increased although responding was increased during the initial part of each interval.