Response acquisition with intermittent immediate and delayed conditioned reinforcement

The acquisition of lever pressing by rats was studied under intermittent immediate and delayed conditioned reinforcement. Rats were exposed to two schedules operating concomitantly. One was a random-time schedule that delivered reinforcers on average of once per min. Each such reinforcer was paired with a 1-s illumination of a cue light located above the lever. The other was a tandem random-interval (RI) t₁ - s fixed-time (FT) t₂ - s schedule that controlled the rate and the delay of the illumination of the cue-light after a given lever press. For the RI, t₁ was 7.5, 15 or 30 s. For the FT, t₂ was 0, 1, 2, 4, 8, 16 or 32 s. Three rats each were exposed to each combination of RI and FT values for 40 sessions. Response rates decreased with longer response-conditioned reinforcer (S(r)) delays under the three different overall rates of S(r). At most response-S(r) delays, absolute response rates were higher with RI 15 s than with RI 30 s but both were similar to those obtained with RI 7.5 s. The results were similar to those from previous research on response acquisition with delayed primary reinforcement. These findings suggest that a previously neutral stimulus that has been correlated with primary reinforcement can reinforce new responses even when the conditioned reinforcer is intermittent and delayed from the responses that produce it.