Avoidance response rates during a pre-food stimulus in monkeys

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.

Suppression of random-ratio and acceleration of temporally spaced responding by the same prereward stimulus in monkeys

A 1-min tone and light signal that preceded two free pellets of food suppressed the random-ratio responding of four rhesus monkeys, but accelerated the same subjects' responding on a differential-reinforcement-of-low-rate schedule in separate sessions. Both schedule-specific interactions occurred during the first presentations of the signal that previously had been paired with food outside the operant sessions. Thus, neither effect was adventitiously produced. In two subjects, both the direction and magnitude of the prereward change in differential-reinforcement-of-low-rate responding appeared related to baseline response rates: the more rapid the baseline responding, the less was the acceleration during the signal. Suppression and acceleration did not appear as dichotomous effects with separate parameters, but as related effects at least partly determined by the characteristics of the baseline operant performance.