Question

According to Rescorla-Wagner, combining two or more conditioned stimuli with a single US:

A. Strengthens the association between both of the CS and the US

B. Blocks the association between both of the CS and the US

C. Blocks the association between one of the CS and the US

D. Weakens the association between both CS and the US

Answer 1

Answer: C

This is seen in the blocking experiment done by Kamin. There were 2 groups of rats, a blocking group and a control group. In the first phase of the experiment, subjects in the blocking group received a series of L+ (Light and shock) trials and by the end of this phase L elicited a strong CR. In phase 2, the blocking group received a series of LT+ (Light and Tone presented together leading to shock) . All these trials were same for the 1st group in phase 2 except that a second CS, T occurred along with L. In the test phase, T was presented by itself in extinction for several trials so as to measure the strength of conditioning to the CS.

Both groups in the experiment received exactly the same number of pairings of stimulus T and shock still Kamin found different results. He observed a strong CR to T in the control group; he recorded no conditioned responding at all to T in the blocking group. Since the only difference between the 2 groups was that the blocking group received conditioning trials with L in Phase 1 but the control group did not.

Kamin thus concluded that this prior conditioning trials with L somehow 'blocked' the later conditioning of stimulus T.

Therefore, when two or more condiotioned stimulus are combined with a single unconditioned stimulus, the association between one of the CS and US gets blocked.