Conditional Acceleration and External Disinhibition of Operant Lever Pressing by Prereward, Neutral, and Reinforcing Stimuli

Abstract

Rats responding under a differential-reinforcement-of-low-rate schedule increased their rates of lever pressing during a 20-second click/flash stimulus that preceded the delivery of a response-independent food pellet. The increase could not be attributed to suppression of collateral behavior that has been said to mediate temporally-spaced responding. We propose that the prereward stimulus functioned as an external disinhibitor of lever pressing that had been inhibited by the constraints of the operant schedule. Support is derived from the observed disinhibitory effects of a 10-second unpaired click/flash stimulus and of unsignaled, response-independent pellets that were presented while the animals were responding under the same schedule.Key words: conditional acceleration, response-independent reinforcement, disinhibition, collateral behavior, differential-reinforcement-of-low-rate, lever press, rats When prefood or preshock stimuli are presented to an animal that is engaged in operant responding, the animal's rate of responding often shows sharp changes. The most frequently observed outcome is a decrease in rate of responding (conditional suppression). However, when responding is maintained by a differential-reinforcement-of-low rate (DRL) schedule, conditional acceleration is frequently observed. For example, Henton and Brady (1970) found that rhesus monkeys responded more rapidly under DRL schedules during a prefood stimulus. Kelly (1973) also found conditional acceleration in rhesus monkeys under similar conditions. However, when the same monkeys were exposed to the prefood stimulus while responding under a random-ratio (RR) schedule, response rate during the signal decreased. Blackman (1968)

Temporal Control in a Complex Environment: An Analysis of Schedule‐related Behavior

“…There was little to support a contention that the timing of the operant was dependent upon the pattern, sequencing, or temporal distribution of the preceding activities. These results are also consistent with those of Hemmes and Rubinsky (1982), who observed wheel running, chewing, and drinking in rats that were lever pressing on a DRL schedule. Wheel running, the most frequent activity, was prevented and two of the three rats showed no increase in lever-pressing rates.…”