Effects of chlorpromazine on food-maintained and observing behavior.

Pigeons were trained to peck each of two response keys. Periods during which pecks on one key (the food key) produced access to grain according to a random-ratio 80 schedule alternated irregularly with periods during which food-key responses had no scheduled consequences (extinction). Both keys remained amber unless a random-ratio 8-response requirement on the second key (the observing key) was met. Completion of the observing-response requirement darkened the observing key and illuminated the food key either red or green for 15 s, depending on whether food could be obtained by pecking the food key. Food-key response rate was high and constant when food could be obtained (and the key was illuminated red). Observing-key response rate was somewhat lower but also constant when the observing key was amber, and near zero otherwise. Increasing doses of chlorpromazine (0.03-17.0 mg/kg, IM) decreased food-key response rate, but sometimes increased observing-key response rate. Additionally, larger doses were required to decrease response rate on the observing key. The differential effect of chlorpromazine upon the two performances may have been due to differences in reinforcer type (conditioned versus unconditioned) or other aspects of reinforcement.