Appetitive–Aversive Interactions: Superconditioning of Fear by an Appetitive CS

Four groups of rats received conditioned suppression training in which a tone and light compound was reinforced with shock. If the light had been previously paired with free food, enhanced fear conditioning accrued to the tone during compound training relative to control groups pre-exposed to the light alone, the light semi-randomly associated with food, or the light unpaired with food. The second experiment replicated the difference in aversive conditioning for the groups receiving the light either paired or unpaired with food. The results are discussed in terms of the functional similarity of a conditioned excitor for food and a conditioned inhibitor for shock.

Conditioned Suppression and Acceleration of Two Concurrent Responses in Rhesus Monkeys

Two rhesus monkeys were exposed to conditioned suppression training in which a 20-sec. stimulus, terminated by unavoidable shock, was superimposed upon a variable interval 90-sec. reinforcement schedule. A concurrent response which had no programmed consequence was recorded during initial variable interval training, acquisition, extinction, and reacquisition of conditioned suppression of the reinforced lever-pressing response. A peak in the distribution of response 2 reliably occurred 30 to 75 sec. following the average lever-pressing (response 1) reinforcement interval. With suppression training, the presentation of the suppression stimulus was reliably followed by a changeover from response 1 to response 2; the presentation of the unavoidable shock immediately resulted in a changeover from response 2 to response 1. The rate of response 2 during the suppression stimulus declined to near zero during extinction of conditioned suppression and increased to a high rate when the suppression stimulus was again terminated by unavoidable shock. The rate of response 2 was dependent upon the intensity of the unavoidable shock.