 a series of experiments is described in which operant methodology is used to study the effects of drugs on " learning . " 
 emphasis is placed on the technique of repeated acquisition as a behavioral baseline for studying this type of transition state . in this technique 
 , each subject is required to learn a new discrimination each session . 
 multiple - schedule procedures are also described in which acquisition is compared to a " performance " task , where the discrimination is the same each session . 
 the learning baseline is more sensitive to the disruptive effects of a variety of drugs ( e.g. , cocaine , d - amphetamine , haloperidol ) than is the performance baseline . 
 this general finding obtains across procedural variations and species ( pigeons and monkeys ) . 
 the potential usefulness of these procedures for studying both acute and chronic behavioral toxicity is discussed.imagesfigure 8.figure 9 . 
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