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| Int'l Paper Session - Timing |
| Monday, May 30, 2005 |
| 10:30 AM–11:20 AM |
| Private Dining Room 3 (3rd floor) |
| Area: EAB |
| Chair: Lauren Duffy (Texas Christian University) |
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| Acquisition Versus Steady State in the Time-Left Procedure |
| Domain: Basic Research |
| ARMANDO MACHADO (University of Minho, Portugal), Marco Vasconcelos (Purdue University) |
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| Abstract: We report the results of two experiments designed to test Scalar Expectancy Theory (SET) in the time-left procedure. Pigeons were initially exposed to two fixed-interval schedules, an FI 30 s and an FI 60 s. The two FIs were associated with distinct keys and were presented on separate trials. Subsequently, during test trials, the FI 60-s key was illuminated and then, after 15, 30, or 45 s had elapsed since trial onset, the FI 30-s key also was illuminated. SET predicted that a) preference for the FI 30-s key would be weaker the later that key was introduced into the test trials, and b) the result described in a) would be obtained since the very first test trials. The results from both experiments showed that prediction a) was confirmed but not prediction b). That is, preference changed reliably from acquisition to steady state, which suggests that learning took place during the test trials. We discuss the implications of these findings for theories of timing. |
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| Temporal Dynamics and Reinforcer Duration: Determining Relevant Time Markers in Interval Schedule Performance in Pigeons |
| Domain: Basic Research |
| LAUREN DUFFY (Texas Christian University), Kaity Volpe (Texas Christian University), Jennifer J. Higa (Texas Christian University) |
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| Abstract: Previous studies have shown that under certain conditions temporal performance on fixed interval (FI) schedules depends on the duration of the reinforcer. For example, postreinforcement pause (PRP) is longer with longer reinforcer durations. This result is unexpected because it means that timing is based on an event that is irrelevant to when a reinforcer will be available. A possible explanation is that animals are timing more than the interval requirement and include the duration of the reinforcer, so that the total cycle time drives behavior in the next interval. To test this idea, we exposed eight pigeons to a response-initiated delay (RID) schedule during which pigeons received reinforcers ranging from two to ten seconds. The total cycle time – time to the first response, delay to reinforcement, and reinforcer duration – was set to 60 s. Trial-by-trial and molar measures of performance during acquisition and the effects of reinforcer duration will be presented. The findings will be discussed in terms of models of timing including scalar expectancy theory and the multiple-time scale model. |
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