Simultaneous second-order conditioning produces S-S learning in conditioned suppression.

Four experiments explored the consequences of simultaneous second-order conditioning of one stimulus (S2) by another (S1) in a conditioned suppression preparation. In two experiments, that mode of presentation produced second-order conditioning of S2 which was attenuated by subsequent extinction of S1. Sequential presentation of the same stimuli produced similar levels of conditioning of S2 which were not affected by extinction of S1, results that replicate previous findings. Two additional experiments found tht the sensitivity of a simultaneous S2 to changes in S1 also depended on that S1 receiving few separate reinforced or nonreinforced presentations prior to second-order conditioning . The results suggest circumstances under which the typical stimulus-response learning observed in second-order conditioned suppression can be converted into stimulus-response learning. An interpretation is suggested in terms of simultaneous presentation generating a unitary representation involving both S2 and S1 rather than an association between them.