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Reward magnitude and trial spacing modulate autoshaped barpressing in rats

Reward magnitude and trial spacing modulate autoshaped barpressing in rats. Stephanie Damas, Kim Ironmonger, Melissa Herd, Ivonne Radinson, Cheryl Novak and Brian Thomas. Autoshaping. Jenkins & Moore’s (1973) approach and contact behavior in pigeons Key light on (10 s)  key light off  food

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Reward magnitude and trial spacing modulate autoshaped barpressing in rats

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  1. Reward magnitude and trial spacing modulate autoshaped barpressing in rats Stephanie Damas, Kim Ironmonger, Melissa Herd, Ivonne Radinson, Cheryl Novak and Brian Thomas

  2. Autoshaping • Jenkins & Moore’s (1973) approach and contact behavior in pigeons • Key light on (10 s) key light off  food • Keypecks per minute was the measure of autoshaping

  3. Purpose • Study autoshaping in rats • Investigate affect of trial spacing on autoshaping • Investigate affect of reward magnitude on autoshaping • Investigate interactive affects of trial spacing and reward magnitude on autoshaping

  4. Design • 8 groups, 8 rats per group • Trial spacing: 15 or 90 seconds • Reward magnitude: 1 or 5 pellets • ABA reversal designs: • 151 vs. 111 • 515 vs. 555

  5. Procedure • 10 trials per session, 2 sessions per day • 15 sessions per phase • Trial: lever inserted (10 s)  lever retracted  food • Amount of food was 1 or 5 pellets • Time between trials was 15 or 90 s • Barpresses per minute averaged over the 10 trials per session was dependent variable.

  6. 515 • In phase I, barpressing was greater with spaced trials than massed (F(14, 588)=5.85, p < .001). • In phase II, a shift from large to small reward marginally increased responding with massed trials (F(1,14)=3.16, P<.10). Similar shifts had no effect with spaced trials. • In phase III, a shift from small to large reward significantly decreased responding with massed trials (F(14, 196)=2.05, p<.02). Similar shifts had no effect with spaced trials.

  7. 151 • In phase I, barpressing was greater with spaced trials than massed (F(14, 588)=5.85, p < .001). • In phase II, a shift from small to large reward significantly decreased responding with massed trials (F(14,70)=4.67, p<.001). Similar shifts had no effect with spaced trials. • In phase III, a shift from large to small reward significantly increased responding with massed trials (F(14,70)=3.18, p<.001). Similar shifts did not affect responding with spaced trials.

  8. Conclusions • Autoshaped responding in rats is facilitated with spaced trials. • Autoshaped responding with spaced trials is not influenced by reward magnitude. In contrast, responding with massed trials is facilitated with smaller rewards. • Large rewards and massed trials may encourage goal-directed rather than signal-directed behavior (Papini & Brewer, 1994).

  9. Possible implications for human learning • The trial spacing effect may not reflect solely a failure to learn when information is presented in a massed fashion. • Larger rewards do not necessarily predict greater performance of a desired response. • In classical conditioning, the spacing of trials seems primary and the role of reward magnitude secondary.

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