Pavlovian conditioning with sexually relevant UCS: which is the necessary UCR?

In Experiment 1, four groups of male rats were subjected to Pavlovian conditioning of an approach response. In one group the reinforcer was one mount with a sexually receptive female and in another group it was one intromission. A third group was deprived of food for 8 h before every session and a fourth group was deprived for 16 h. These latter groups received a 94 mg food pellet as reinforcement. The conditional stimulus (CS)+ and CS- were different lights. Rats reinforced with mount, intromission, or food after 16 h of deprivation learned to approach the CS+ more than the CS-. There was no difference in performance between the groups making one mount and one intromission. Rats deprived of food for 8 h failed to discriminate between the CS+ and the CS-. The results obtained with food reinforcement show that performance in the conditioning procedure depends on the level of motivation, which should be the case in any valid procedure. In Experiment 2 we determined whether access to female odor, exposure to an inaccessible female, one mount, and one intromission could reinforce classical conditioning. Only mount and intromission were efficient. These data show that the earliest event in the sequence of sexual behaviors that can promote conditioning is mounting. The fact that mount and intromission are equally efficient for reinforcing Pavlovian conditioning shows that the somatic and visceral responses associated with these behavior patterns rather than sensory feedback from the genitals are crucial.