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The Probability of Reinforcer Delay as a Determinant of Preference for Variability

The Probability of Reinforcer Delay as a Determinant of Preference for Variability. Michelle Ennis Soreth , Concetta Mineo , Jeffrey Walsh, Thomas Budroe , & Alec Ward. Preference for Variability.

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The Probability of Reinforcer Delay as a Determinant of Preference for Variability

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  1. The Probability of Reinforcer Delay as a Determinant of Preference for Variability Michelle Ennis Soreth, ConcettaMineo, Jeffrey Walsh, Thomas Budroe, & Alec Ward

  2. Preference for Variability • Organisms generally prefer working in situations with variable outcomes over situations with fixed outcomes. • This phenomenon is largely determined by a occasional quick or large payoff imbedded in the variable situation.

  3. Past Research • Pigeons prefer working on VI schedules over FI schedules that have the same arithmetic mean (Herrnstein, 1964). • Led to conclude that thevalue of the VI reinforcers are weighted differently than the value of the FI reinforcers • Mean may not be the best way to characterize the value of the VI schedule/reinforcers • However, when the occasional short intervals were removed from the VI schedules, the preference for the FI did NOT become exclusive (Andrzejewskiet al, 2005; Soreth & Hineline, 2009). • Suggest that the occasional quick payoff is not the sole determinant of the preference for variability

  4. Method • A concurrent-chains arrangement with fixed interval (FI) and random interval (RI) terminal link alternatives. • RI schedule maintained a rate of reinforcement half that of the FI alternative. • RI 30 (Reinforcer produced on average once every 30 s) • FI 15 (Reinforcer always produced by the first response after 15 s) • RI schedule never produced a component interval value less than that of the FI schedule. • Shortest interval available on RI = 15 seconds, often longer • Interval ALWAYS available on FI = 15 seconds

  5. Four pigeons were exposed to the procedure in daily experimental sessions • 40 choice trials per day • Preference was assessed as the % of RI terminal link trials per session • Probability of obtaining the smallest programmed delay to reinforcement Pr[minRI] on the RI schedule is to be manipulated across conditions • The probability of producing the shortest RI variable was .50 • Future testing will include .03 and .97 probabilities.

  6. Terminal Link Begins 100% chance SR+ available 0 s 15 s FI 15 RI 30 • Future work in this experiment will have the pigeons additionally exposed to Pr[minRI] variables for: • RI 60 s vs. FI 30 s • RI 90 s vs. FI 45 s 50% chance reinforcer delay longer than 15 s 50% chance SR+ available 0 s 15 s

  7. References Andrzejewski, M.E., Cardinal, C.D., Field, D.P., Flannery, B.A., Johnson, M., Bailey, K., & Hineline, P.N. (2005). Pigeons’ choices between fixed and variable interval schedules: Utility of variability? Journal of the Experimental Analysis of Behavior, 83, 129-145. Herrnstein, R.J. (1964). Aperiodicity as a factor in choice. Journal of the Experimental Analysis of Behavior, 7, 179-182. Soreth, M.E., & Hineline, P.N. (2009). The probability of small schedule values and preference for random-interval (RI) schedules.

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