Effect of prior Pavlovian discrimination training upon learning an operant discrimination

The effect of Pavlovian discrimination training with two stimuli upon subsequent learning of an operant discrimination involving those stimuli was studied. After preliminary lever press training, the lever was removed and thirsty rats received noncontingent pairings between S₁ (a tone or a clicker) and water reinforcements, whereas S₂ (a clicker or a tone) occurred always without reinforcement. This procedure presumably established S₁ as a positive CS for respondent behavior, whereas S₂ was established as an inhibitory CS. Following this training, the lever was reintroduced and the rats were trained on an operant (lever pressing) discrimination involving S₁ and S₂. For the Consistent Ss, S₁ was the S^D and S₂ the S^Δ in the operant discrimination; for the Reversed Ss, S₂ served as S^D and S₁ as S^Δ. The Consistent Ss learned the operant discrimination significantly faster than did the Reversed Ss. The result emphasizes the importance of respondents, conditioned to S^D and S^Δ, which modulate operant performance to these stimuli.