Conditioning flavor preferences in rats: Dissecting the “medicine effect”

Abstract

Four experiments examined conditioning parameters governing enhanced flavor preferences in rats (i.e., Green & Garcia's, 1971, “medicine effect”). In Experiments 1–3 rats were concurrently conditioned to avoid flavor A and to prefer flavor B after multiple-trial pairings with a toxin. In Experiment 2, rats learned to avoid saccharin and to prefer vinegar when they tasted these flavors 30 and 75 min after being injected with lithium. Concurrent conditioning of two flavors (one aversive, the other preferred) was compared with preference-only conditioning in Experiment 3. Though no differences in acquisition were found, extinction of the conditioned aversion to flavor A accelerated extinction of preference to flavor B. In Experiment 4, conditioned preference was found to retard acquisition of conditioned aversion. Conditioned flavor preferences (1) are reliably and easily produced, (2) once expressed are resistant to extinction, and (3) are most likely described as conditioned inhibition.