Date of Award


Degree Name

Doctor of Philosophy



First Advisor

Jacobs, Eric


Three experiments arranged a concurrent chained schedule that probabilistically arranged reinforcement or extinction. In Experiments 1 and 2, the probability of obtaining food in the terminal link period, following a given left or right lever choice, was the complement of the probability that the initial link choice would produce a transition to the terminal link. Also, the probability of reinforcement in the terminal link was either signaled or unsignaled, depending upon condition. In Experiment 1, a steady-state environment kept the relative probabilities of reinforcement constant within-session and Experiment 2 varied the relative probabilities of reinforcement within-session. Experiment 3 arranged equal rates of terminal link transition to either a signaled-reinforcement or an unsignaled-reinforcement terminal link. The location of the signaled option and the relative probabilities of reinforcement changed within-session. The signaled option produced either a reinforcement-correlated terminal link stimulus (i.e., conditional reinforcement) or an extinction-correlated terminal link stimulus. The unsignaled alternative produced the same terminal link stimulus regardless of the outcome. Overall, Experiments 1 and 2 demonstrated that rats frequently favor the option providing higher rates of terminal link transition at the expense of the probability of terminal link unconditional reinforcement. However, in Experiment 2, this tendency was reduced when the probabilities of reinforcement were signaled, suggesting weak control by conditional reinforcement. Experiment 3 did not show preference for the reinforcement-correlated signaled option in rats. Rather, it appears overall preference was controlled by an avoidance of the extinction-correlated option.




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