A demonstration of the graded nature of the generalization function of drug discrimination learning within the...

Although control of discriminative performance will often generalize to different doses of the training drug or to drugs from the same class as the training drug, the nature of this generalization is unknown. Prior work has suggested that the generalization is primarily quantal in nature with animals displaying either vehicle-appropriate or drug-appropriate responding, depending upon their detection of the drug stimulus. It has been questioned whether this quantal nature of generalization reflects a characteristic response to drug stimuli or whether such responding is a function of the specific training and testing procedures used to establish and measure drug discrimination learning. The present paper evaluated this issue by analyzing the generalization functions of individual subjects trained and tested within one specific drug discrimination procedure, i.e. the conditioned taste aversion design. Responding within this design was generally graded. It is clear that quantal responding is not a necessary outcome of drug generalization assessments and that the nature of generalization in drug discrimination learning is a function of the specific procedure utilized in training and testing the discrimination. The results of the present analysis are discussed in terms of other recent work reporting graded functions.