Schedules of Reinforcement CH 17,18,19
Divers of Nassau • Diving for coins • Success does not follow every attempt • Success means reinforcement
Intermittent Reinforcement • A reinforcer follows the response only once in a while.
Continuous Reinforcement (CRF) • A reinforcer follows every response. • Best used for shaping or maintaining difficult behavior.
Shaping with Reinforcement Reinforcement Behavior Initial: Andrew moves lips Intermed: Andrew makes croaking sound Terminal: Says words clearly After: Andrew receives gum Before: Andrew has no gum Behavior Initial: NA Intermed: Moves lips only Terminal: Says words unclearly After: Andrew receives no gum Extinction
Schedule of Reinforcement • The way reinforcement occurs because of the number of responses, time between responses, and stimulus conditions.
Schedules of Reinforcement • Ratio • Fixed Ratio (FR) • Variable Ratio (VR) • Interval • Fixed Interval (FI) • Variable Interval (VI)
Fixed Ratio (FR) Schedule of Reinforcement • A reinforcer follows a fixed number of responses.
FR Responding • After a response is reinforced, no responding occurs for a period of time, then responding occurs at a high, steady rate until the next reinforcer is delivered.
Reinforcers Reinforcement always immediately follows the 5th response!!!! This is an FR5 schedule of reinforcement. Pauses
Postreinforcement Pause (PRP) • The name for the pause after the consumption of the reinforcer and before the next ratio of responses begins.
FR & PRP • Length of the pause is proportional to the size of the ratio. • Small ratio – pausing is short • Large ratio – pausing is long
General Rule for establishing intermittently reinforced behavior:First use CRF and gradually increase the intermittency of reinforcement as responding stabilizes at a high rate.
FR120 • What are the response requirements? • When will reinforcement be delivered? • What will the pattern of responding look like?
Cumulative Graph for FR Post reinforcement pauses Reinforcers
Variable Ratio (VR) Schedule • A reinforcer follows after a variable number of responses
VR Responding • VR schedules produce a high, constant rate of responding, with almost no postreinforcement pausing.
VR 50 • Schedule notation • Number designates the average number of responses required for reinforcement
How do typical schedules of reinforcement differ from gambling? • See pages 290-291
Time Dependent Schedules • Fixed Interval (FI) • Variable Interval (VI)
FI Schedule of Reinforcement • A reinforcer is contingent on the first response after a fixed interval of time since the last opportunity for reinforcement.
Example: Fixed Interval (FI) Schedule of Reinforcement FI 200-s 200 seconds 400 seconds 600 seconds
Fixed-Interval Scallop • A FI schedule often produces a scallop – a gradual increase in the rate of responding with responding occurring at a high rate just before reinforcement is available. No responding occurs for some time after reinforcement (Post Reinforcement Pause.
Example: Fixed Interval (FI) Schedule of Reinforcement FI 200-s PRP Scallop 200 seconds 400 seconds 600 seconds
Term paper vs. FI • Term paper does not have a deadline.
Fixed Time & Superstitious Behavior • Fixed time schedules of reinforcement • A reinforcer is delivered after the passage of a fixed period of time, independently of the response. • Superstitious behavior • Behaving as if the response causes some specific outcome when it really does not.
Superstitious behavior of the pigeon:Experiment by SkinnerFixed Time Schedule
Variable Interval (VI) Schedule of Reinforcement • A reinforcer is contingent on the first response after a variable interval of time since the last opportunity for reinforcement.
VI Responding • VI schedules produce a moderate rate of responding with almost no postreinforcement pausing.
Comparing/Contrasting Ratio and Interval Schedules • Pg. 305: table • Pg. 305: cumulative records
Continuous vs. Intermittent • CRF – every response is reinforced • Intermittent reinforcement – only some responses produce a reinforcer.
Intermittent Reinforcement • Makes the response more resistant to extinction than does continuous reinforcement.
Resistance to Extinction • The number of responses or the amount of time before a response extinguishes
Resistant to Extinction and Intermittent Reinforcement • Intermittent reinforcement makes the response more resistant to extinction than does continuous reinforcement. • Why? Hard for the rat to tell the difference between only an occasional reinforcement and no reinforcement • CRF followed by EXT: rats quickly stop responding: easy discrimination between reinforcement & extinction contingencies
4 Types of Concurrent Contingencies • Two compatible responses • Compatible contingencies for a single response • Incompatible contingencies for a single response • Two incompatible responses
Concurrent Contingencies • Contingencies that are available at the same time. • More than one contingency of reinforcement or punishment is available at the same time.
Concurrent Contingencies • Two levers in chamber • VI 300 s on Left lever • VI 30 s on Right lever • Will animal allocate more responses to the left or the right lever? • Matching Law (pg. 330) % of Left lever presses = % Left-lever reinforcers
Matching Law • Relative Frequency of responding on two concurrent schedules of reinforcement equals the relative value of reinforcement on those two schedules