Four groups of thirsty rats received training with a compound stimulus (i.e., tone plus light) paired with an unconditioned stimulus (US) during responding for water. Two groups were given additional pairings of A (e.g., tone) and the US (A+) either before (Group A+AX+) or after (Group AX+A+) to AX+ training. Another group received non-reinforced A- presentations after AX+ training, and the remaining group received only AX+ training. Then, all groups were tested for the degree of suppression to X (e.g., light). Although prior conditioning of A attenuated suppression to X (blocking), postconditioning of A enhanced suppression to X. Non-reinforced A presentations after AX+ training had the same effect as AX+ alone. Finally, all groups underwent extinction to A and were tested for suppression to X again. Blocking was preserved in Group A+AX+, but the enhanced suppression to X observed in Group AX+A+ disappeared after extinction of A. These results were accounted for by a within-compound association view.

Key words: rats, Pavlovian conditioning, conditioned suppression, within-compound association, blocking