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| Changeover |
| Tuesday, June 1, 2004 |
| 12:00 PM–1:20 PM |
| Commonwealth |
| Area: EAB |
| Chair: Angel Jimenez (University of Guadalajara, Mexico) |
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| Stay and Switch Reinforcers When Using a COD: Within-Subjects Comparisons |
| Domain: Applied Research |
| JAMES S. MACDONALL (Fordham University) |
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| Abstract: A recent approach to understanding performance in concurrent choice considers the performance and contingencies at each alternative as independent of the other alternative (MacDonall 1998, 1999, 2000). At each alternative of a concurrent VI schedule one contingency arranges reinforcers for staying at that alternative as the other contingency arranges reinforcers for switching to the other alternative (Houston & McNamara, 1981). Previous research showed that performances at the alternatives, run lengths and visit durations, were power functions of the ratio of the rates of reinforcers for staying divided by the rates of reinforces for switching. Between-subjects comparisons showed that a COD reduced the switching rate, as it does in concurrent procedures, while producing good fit by the power function. The purpose of the present experiment was to make within-subjects comparisons of the effect of a COD by using a two-component multiple schedule. Results indicate that the effects of a COD are similar, whether using one pair of stay and switch schedules or two pairs of stay and switch schedules, that is, a concurrent procedure. These results support the view that concurrent performances consist of two independent performances joined by the changeover response. |
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| Haloperidol, Choice Behavior, and Dynamic Fixed-Ratio Changeover Requirements |
| Domain: Applied Research |
| CARLOS F. APARICIO (University of Guadalajara, Mexico), Francisco Velasco (University of Guadalajara, Mexico), Jorge Arturo Balderrama Trapaga (University of Guadalajara, Mexico) |
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| Abstract: In choice situations that simulate a variable reinforcing environment, haloperidol does not affect the rat’s discrimination between rich and lean alternatives. But, residence and travel times increase, and response distribution changes. These results suggest that haloperidol impairs the motor system affecting the behavior of traveling from one site to another. We tested the generality of these findings in a choice situation with two main levers, and one changeover-lever. Every ten reinforcers, a different number of responses (1, 4, 8, 16, or 32) were required to switch from one lever to the other. Across conditions, the ratio of reinforcement changed seven times in random and without signaling. After 148 days that the rats gained enough experience, two doses of haloperidol (0.04 & 0.16 mg/kg) were assessed (ip) over a period of 48 days. Results showed that haloperidol did not extinguish the behavior of pressing on the levers for food, but response allocation varied across components. As it was indicated by the parameters, s and b of the generalized matching law, haloperidol affects the organism’s preference and increases its sensitivity to reinforcement. We will discuss the implications of these results for a general model of anhedonia. |
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| Varying the Changeover Requirement in Dynamic Reinforcing Environments |
| Domain: Applied Research |
| ANGEL JIMENEZ (University of Guadalajara, Mexico), Carlos F. Aparicio (University of Guadalajara, Mexico) |
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| Abstract: The study of choice in steady state has shown that sensitivity to reinforcement increases with increasing changeover requirements. We tested the generality of this finding with rats responding for food in two different dynamic environments. Two random interval components dependently scheduled provided food in two levers according to seven reinforcement ratios (27:1, 9:1, 3:1, 1:1, 1:3, 1:9 and 1:27). An ABA experimental design was used to vary a fixed-ratio (1, 2, 4, 8, 16 and 32 responses) changeover requirement. In phase A, each changeover requirement was assessed in ascendant and descendent order. Phase B scheduled all changeover requirements to occur within the same session, 12 days for each of the seven reinforcement ratios. Results showed that response and time allocation adjusted rapidly to dynamic changes in reinforcement ratios. Interchangeover times and sensitivity to reinforcement increased with increasing changeover requirement, but changeover rate decreased. The roles of experience in the reinforcing environment and that of imposing a cost to the behavior of switching from one lever to the other will be discussed in light of an integration between molar and molecular approaches of choice. |
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