The acquired reward value of an intermittently presented neutral stimulus.

Abstract

Six groups of hooded rats were conditioned to press a bar for food. For one pair of groups a buzzer sounded on half the occasions the bar was pressed. For a second pair of groups the buzzer was present on each bar response, and for a final pair of groups the buzzer was never present during conditioning. In extinction the buzzer sounded when one group in each pair pressed the bar. Intermittent presentation of the buzzer during conditioning (whether the buzzer was present or absent in extinction) led to a significantly greater number of extinction responses than when the buzzer was present repeatedly in conditioning and absent in extinction, or absent in conditioning and present repeatedly in extinction. No unequivocal evidence was provided that an intermittently presented neutral stimulus could acquire reward value. The role played by stimulus generalization in studies involving secondary reinforcement was discussed.