Long-delay learning in the pigeon: flavor, color, and flavor-mediated color aversions

Abstract

In Experiment 1a, consumption by pigeons of a distinctively flavored solution was followed by toxicosis either 0, 3, 6, 9, or 12 hr later. The aversions produced were strong and also a decreasing function of the CS—US interval, with substantial aversions occurring at a 9-hr delay. In Experiment 1b, consumption by pigeons of a distinctively colored solution was followed by toxicosis at these intervals. The aversions produced were weak and also a decreasing function of the CS—US interval, with no aversions occurring at delays of 3–6 hr. A within-experiment comparison of the strengths of separately conditioned flavor and color aversions across delays (Experiment 2a) confirmed that flavor aversions were stronger and survived longer delays than color aversions. A similar comparison after conditioning to the flavor—color compound (Experiment 2b) showed that color aversions were as strong or stronger than flavor aversions when the compound was followed by immediate toxicosis but that color aversions were abolished, although flavor aversions remained substantial, when the compound was followed by delayed toxicosis. The data were interpreted: (a) to have attested to the primacy of taste in the formation of food aversions, (b) to have confirmed the mediational role of taste in the formation of aversions to the exteroceptive attributes of a food object, and (c) to have provided difficulties for a sensory preconditioning model of the mediation process.