Avoidance and classical conditioning of leg flexion in dogs.

This study of leg flexion conditioning in dogs, which were trained under both avoidance and classical contingencies consecutively, confirmed and extended the results from the Wahlsten and Cole study (In Classical Conditioning II: Current Research and Theory, Appleton Century-Crofts, New York, 1972). Briefly, dogs were trained to asymptotic behavioral levels under either avoidance or classical contingencies with a CS-US interval of either three (3) or five (5) seconds where the unconditioned stimulus (US) was shock to the foreleg and the conditioned stimulus (CS) was 1000 Hz tone. The dogs were then switched to the other contingency (without any modification in the stimulus situation other than the shock contingency) and trained to asymptotic behavioral levels. The CS remained on for the entire CS-US period and terminated with the end of the scheduled interval. Under the classical contingency, the US occurred as scheduled on every trial regardless of the dog's behavior. Under the avoidance contingency, the US was prevented from occurring if the subject responded with a criterion leg lift during the CS-US interval. The only feedback to the dog of a successful performance was the leg lift itself. The results indicated that there were two different conditioned responses produced, one just after CS onset under the avoidance contingency, and one just before US onset under the classical contingency for both CS-US intervals. The findings were interpreted as supporting a single-factor informational view of learning and a neural model was presented.