Joint effects of ethanol and caffeine on schedule-controlled responding in the pigeon.

Interactions between ethanol and caffeine were studied in pigeons keypecking under a multiple fixed ratio 30 fixed interval 5-min schedule of food presentation. When ethanol was administered alone, rates of responding under both components of the multiple schedule were generally decreased in a dose-related manner. Caffeine alone either decreased or had no effect on rates of responding under both the fixed ratio and fixed interval components. When caffeine and ethanol were combined, doses of caffeine which did not decrease rates of responding when given alone attenuated the rate-decreasing effects of ethanol.