Schedules of Reinforcement

1. Schedules of Reinforcement Thomas G. Bowers, Ph.D.

2. How is behavior maintained? • Simplistic to simply think uncomplicated contingencies operate in the day to day environment • Patterns of reinforcement, patterns of conditioning, relate in a complex fashion with the characteristics of the organism

3. Schedules of Reinforcement • Yield predictable and orderly patterns of behavioral responses • Most patterns of reinforcement are intermittent • More recently, theorists have also attended to the economic aspects of intermittent reinforcement

4. Schedules of Reinforcement • Basic Schedules • 1. Fixed Interval Schedules (FI) • A single response after the passage of a fixed period of time yields reinforcement • Responses during the interval are not reinforced • 2. Variable Interval Schedules (VI) • A single response after a varied passage of time • e.g. VI2 - after an average passage of 2 minutes

5. Schedules of Reinforcement • Basic Schedules • 3. Fixed Ratio (FR) • Reinforcement occurs after a fixed number of responses • Passage of time irrelevant • 4. Variable Ratio (VR) • Number of responses required for reinforcement vary from trial to trial • e.g. VR 50 reinforces on the average the 50th response

6. Schedules of Reinforcement • Intermittent reinforcement tends to maintain patterns of responding for longer periods of time in extinction • partial reinforcement effect • implies greater response strength

7. Schedules of Reinforcement VR Cumulative Responses VI Time

8. Schedules of Reinforcement FR Cumulative Responses FI Time

9. Schedules of Reinforcement • Some characteristics • 1. Variable schedules tend to develop higher rates of responding relative to fixed schedules • 2. Ratio schedules tend to develop higher rates of responding to interval schedules • 3. Fixed schedules of reinforcement demonstrate a characteristic pause after each reinforcement

10. Schedules of Reinforcement • Some characteristics • 4. Pause of responding after reinforcement on fixed ratio/interval is described as post-reinforcement pause (PRP)

11. Choice Behaviors • Study of Concurrent Patterns of Reinforcement • How is behavior demonstrated in the situation where there are multiple schedules of reinforcement operating? • Organisms respond in direct proportion of the frequency (or density) of reinforcement offered

12. Matching Law • Herrnstein and associates in the 1970s Respon A Respon A + Respon B Rft A Rft A + Rft B =

13. Matching Law • Or, more clearly RA RA + RB ra ra + rb =

14. Matching Law • Magnitude of reinforcement Ra Ra + Rb Ma Ma + Mb =

15. Matching Law • Delay of Reinforcement Ra Ra + Rb 1/Da 1/Da + 1/Db =

16. Matching Law • Allows for more complex processing analysis Ra Ra + Rb ra x Ma x1/Da (ra x Ma x 1/Da) + (rb x mb x1/Db) =

17. Matching Law • Animals tend to respond differentially, with more responses to the smaller immediate reward relative to the larger delayed reward

18. Choice Behaviors • Immediacy of reinforcement can “lock in” an organism to a leaner schedule of reinforcement

19. Matching and Maximizing • Maximizing suggests the animal will demonstrate the response which maximizes the likelihood of reinforcement • This is somewhat different than predicted by matching predictions

20. Matching and Maximizing • Animals tend to distribute responses in relation to the density of reinforcement • This is even true when some patterns results in less over all reinforcement

21. Matching and Maximizing • This effect has been attempted to be explained by optimal foraging theory • Feeding behavior is thought to be sensitive to the amount of energy expended in finding, securing and eating food • There may be adaptive significance to seeking varieties of food sources

22. Economic Concepts • Demand • Some demands are elastic • Others are inelastic • For example, bread is probably inelastic, while movies may be elastic

23. Types of Economies • Open versus closed contingent systems • open systems tend to decrease response rates • holds for both FR and VR schedules

24. Summary • Intermittent schedules of reinforcement leads to greater response strength • Variable schedules of reinforcement yields higher levels of behavior • Ratio schedules of reinforcement also yield higher levels of behavior • Interval schedules demonstrate characteristic patterns of responding

25. Summary • Organisms tend to match reinforcement probabilities rather than maximize reinforcement • Economic aspects influence patterns of contingent behavior