Dual effects of a second-order conditioned stimulus: Excitation and inhibition

On alternate days during Sidman avoidance training, four groups of four Ss each were conditioned in a separate chamber. Group 1 received 10 forward first-order (CS1-US) and 20 forward second-order (CS2-CS1) conditioning trials until 100 of the former and 200 of the latter were completed. For Group 2 second-order trials involved a random contingency. Only the CS1 was presented Group 3 on the first 180 of the 200 second-order trials. Group 4 was like Group 3 except that the last 20 CS2-CS1 trials involved a random contingency. During extinction of the avoidance response onset of CS1 occasioned accelerated response rates for all groups. CS1 offset produced below-baseline response depression. The CS2 accelerated responding for Group 3, depressed performance for Group 1, and left basically unchanged Groups 2 and 4.