Rebecca Singer & Thomas Zentall University of Kentucky

1. A Direct Test of Contrast and Delay Reduction Hypotheses: Why Do Pigeons Prefer Stimuli Following Aversive Events? Rebecca Singer & Thomas Zentall University of Kentucky

2. Justification of Effort Greater value is placed on the reward that requires greater effort to obtain (i.e., A in organic chemistry vs. A in golf)

3. FR1 FR20 + + or ? Justification of Effort in Pigeons Clement, Feltus, Kaiser, and Zentall (2000) Train Test

4. Contrast Effect Proposed contrast hypothesis (rather than cognitive dissonance) to explain results +ΔV Reinforcement Relative Value of Reinforcer Value Relative Value of Reinforcer V FR1 Aversiveness of task -ΔV FR20

5. Delay Reduction HypothesisFantino (1969) Any stimulus that is associated with a reduction in the delay to reinforcement should become a conditional appetitive stimulus

6. FR20 FR1 Presentation of discriminative stimuli Reinforcement Delay Reduction Hypothesis

7. Overall Purpose Purpose of current experiments is to provide a direct test of the delay reduction hypothesis by holding trial duration constant Used two schedules of reinforcement: fixed interval (FI) and differential reinforcement of other behavior (DRO)

8. White White Horiz Vert DRO FI Food Food Right key = FI 20 s Left key = DRO 20 s Experiment 1a – Training

9. White White White White Horiz Vert DRO FI Food Food Experiment 1a – Test

10. Experiment 1a - Results 2 birds demonstrated DRO preference 1 bird demonstrated FI preference 4 birds demonstrated side preference

11. Experiment 1b: Purpose Contrast hypothesis states that pigeons will prefer stimuli associated with their non-preferred schedule (or side) Delay reduction hypothesis states if trial duration is equated there should be no preference for discriminative stimuli

12. White White Horiz Vert DRO FI Food Food Experiment 1b – Training

13. Experiment 1b – Test DRO , FI, or no initial event Both S+

14. Experiment 1b - Results

15. Conclusions There was no systematic schedule preference when FI and DRO schedules were used There was a significant preference for stimuli that followed the aversive schedule