Preexposure to conditioned and unconditioned stimuli in taste-aversion learning

Four groups of rats were compared on the acquisition of a sucrose (50 g/1) aversion produced by sucrose-apomorphine (20 mg/kg) pairings. One group was preexposed to sucrose, another group was preexposed to drug-induced illness, and a third group was preexposed both to sucrose and to drug-induced illness. A fourth group was not preexposed to taste or drug. Results showed that preexposure to either the sucrose or the drug attenuated the acquisition of a sucrose aversion. Preexposure to both sucrose and drug produced a greater deficit in aversion learning than preexposure to either alone. It was concluded that taste preexposure and drug preexposure effects have independent and additive influences on taste-aversion learning.