Delivering Different Reinforcers in Each Half of the Session: Effect of Reinforcement Rate

Abstract

Previous research (Weatherly, Stout, Rue, & Melville, 2000) has shown that rats’ rates of lever pressing for low-concentration liquid-sucrose reinforcement in the first half of an experimental session are higher when food pellets, rather than the same sucrose reinforcers, are delivered in the second half of the session (i.e., induction). The present study investigated whether this effect was sensitive to changes in the rate of reinforcement in the first or second half of the session. Rats responded in 50-min sessions, with 1 % (Experiment 1) or 5% (Experiment 2) liquid-sucrose reinforcers delivered during the first half of the session. In different conditions, food pellets or the same sucrose served as the reinforcer in the second half of the session. Rate of reinforcement in either the first or second half of the session was varied across conditions. Results showed that induction was present in both experiments, although it was most reliable when subjects responded for 1 % sucrose. They also suggest that rate of sucrose reinforcement is not a determining factor of when induction will be observed. By doing so, the present results increase the generality of the present induction effect.