Effects of delays to reinforcement on acquisition of free-operant responding under an FR-1 schedule Data plotted to show the effects of delays. All groups discriminated between the active and the inactive lever, and delays retarded acquisition of the active lever response in both groups. (a) Responding of sham-operated control rats, under all three response-reinforcer delay conditions. (b) Responding of AcbC-lesioned rats under all delay conditions. The next figure replots these data to show the effect of the lesion more clearly.