Document Type



The present study investigated acquisition and extinction of
free-operant responding when rats' lever presses produced sucrose
pellets after resetting delays of 10 or 20 s. Presses on a second
lever cancelled any scheduled food deliveries. Although previous
research using 60-s delays failed to demonstrate maintenance of
responding across repeated sessions, current findings show that
lever pressing can be acquired and maintained with resetting
delays. This was demonstrated by both (a) an increase in lever
pressing across sessions, and (b) an increase across sessions in
the proportion of responding emitted on the lever that produced
reinforcement. In addition, responding decreased quickly and
substantially when extinction was implemented. This investigation
extends previous research showing rats can acquire lever pressing
under the resetting/cancellation conditions, and provides evidence
that the ability of delayed reinforcers to strengthen responding is a
robust phenomenon.