The effects of amphetamine on blocking

In the blocking paradigm, prior conditioning to one stimulus, A, interferes with conditioning to a second stimulus, B, when the two are reinforced as a compound in subsequent training. The present experiment employed a conditioned emotional response (CER) procedure with rats to examine the effects of 1.5 mg/kg dl-amphetamine on blocking. The drug was administered in a 2 x 2 design, that is, drug or no drug in the single stimulus conditioning stage and drug or no drug in the compound conditioning stage. Administration of the drug in either stage alone disrupted blocking. In contrast, animals that received amphetamine in both stages of the blocking paradigm showed a normal blocking effect.