This study supports the hypothesis that the learning of an instrumental response can occur on the first rewarded trial and refutes the hypothesis that reinforcement is dependent upon the confirmation of an expectancy. Immediate secondary reinforcement in instrumental-reward learning appears to be the principle operating here. The essential property of reinforcement is an immediate approach to the food and thus instrumental-reward learning becomes akin to classical conditioning. (PsycINFO Database Record (c) 2006 APA, all rights reserved)