Copyright © 2011 Pearson Education, Inc. All rights reserved. Developing Behavioral Persistence...

Copyright © 2011 Pearson Education, Inc. All rights reserved.

Developing Behavioral Persistence Through the Use of Intermittent

Reinforcement

Chapter 6


Definitions• Schedule of reinforcement –

– rule specifying which occurrences of a given behavior, if any, will be reinforced

• Continuous Reinforcement (CRF): – every correct response is reinforced; fast learning & fast extinction

• Intermittent Reinforcement:– only some correct responses are reinforced; slow learning & extinction


Definitions• Acquisition Phase

– Behavior is being conditioned or learned• Maintenance Phase

– Behavior has become well-learned• Free-Operant Procedure

– Individual is “free” to respond repeatedly– There are no constraints on successive responses

• Discrete-Trials Procedure– Distinct stimulus is presented prior to an opportunity for a response to occur and is followed by reinforcement

– Rate of responding is limited to the rate at which successive stimuli at the beginning of each trial are presented


Intermittent Reinforcement

• Advantages– Reinforcer remains effective longer because satiation takes place more slowly.

– Behavior that has been reinforced intermittently tends to take longer to extinguish.

– Individuals work more consistently on certain intermittent schedules.

– Behavior that has been reinforced intermittently is more likely to persist after being transferred to reinforcement in natural environment.


Ratio Schedules• Based on number of responses emitted• Fixed-ratio (FR) schedule

– Reinforcement occurs each time a set number of responses of a particular type is emitted.• Ratio strain – deterioration of responding from increasing an FR schedule too rapidly

– Produce high steady rate of responding until reinforcement, followed by a post-reinforcement pause• The higher the value of the FR, the longer the pause

– Initially produces high rate of responding during extinction

– Produces high resistance to extinction


Ratio Schedules• Variable-ratio (VR) schedule

– The number of responses required to produce reinforcement changes unpredictably from one reinforcement to the next.

– Produces a high steady rate of responding.– Produces no (or at least very small) post-reinforcement phase

• Differences between VR and FR schedules: – VR schedules can be increased more abruptly than FR schedules without producing ratio strain

– Values of VR that can maintain a behavior are somewhat higher than those of FR

– VR produces higher resistance to extinction than FR of same value does


Simple Interval Schedules

• Schedules based on time• Fixed-Interval (FI) Schedule

– The first response after a fixed amount of time following the previous reinforcement is reinforced and a new interval begins

– Size of FI schedule: amount of time that must elapse

– No limit on how long after the end of the interval a response can occur in order to be reinforced

– FI Schedules produce:• A rate of responding that increases gradually near the end of the interval until reinforcement

• A post-reinforcement pause– Length depends on value of FI – the higher the value, the longer the pause



• Variable-Interval (VI) Schedule– The length of the interval changes unpredictably from one reinforcement to the next

– Lengths of VI schedule vary around some mean value

– Produces a moderate, steady rate of responding and no post-reinforcement pause

– Produces high resistance to extinction– Responding is lower during extinction after VI than after FR or VR



• Simple interval schedules are not often used because:– FI produces long post-reinforcement pauses

– VI generates lower response rates than ratio schedules

– Simple interval schedules require continuous monitoring of behavior after each interval until a response occurs


Interval Scheduleswith Limited Hold

There is a finite time after a reinforcer becomes available that a response will produce it.

–FI/LH–VI/LH


Limited Hold

• Short limited holds – similar results to ratio schedules

• For small FIs, FI/LH produce results similar to FR schedules

• Variable Interval, Limited Hold – similar results to VR schedules

• Used when ratio-like behavior is desired, but unable to count each instance of behavior


Duration Schedule

• Reinforcement occurs after the behavior has been engaged in for a continuous period of time– Fixed Duration (FD) – the period is fixed

– Variable-Duration (VD) – interval changes unpredictably

• Used only when target behavior can be measured continuously


FIGURE 6-1 Diagrams illustrating the differences between the time-based schedules described in the text. In each diagram, the horizontal line represents a period of time. “In a fixed-interval (FI) schedule, a reinforcer is presented following the first instance of a specific response after a fixed period of time (see Figure 6-1).” Page 81


Concurrent Schedulesof Reinforcement

• Schedules of reinforcement that are in effect at any given time

• Herrnstein’s (1961) matching law:– The response rate or the time devoted to an activity in a concurrent schedule is proportional to the rate of reinforcement of that activity relative to the rates of reinforcement on the other concurrent activities.

• Research findings on factors influencing choice of reinforcement:– Types of schedules that are operating– The immediacy of reinforcement– The magnitude of reinforcement– Response effort involved in different options


Pitfalls of Intermittent Reinforcement

• Failure to conduct extinction correctly may turn into intermittent reinforcement– Ex: Child tantrums – ignore first, but then give in

• Failure to introduce intermittent schedule gradually enough may result in loss of the behavior


Guidelines for the Effective Use of Intermittent Reinforcement• Choose appropriate schedule for behavior

you wish to strengthen• Choose schedule that is convenient to administer

• Use appropriate instruments and materials to determine accurately and conveniently when the behavior should be reinforced

• Frequency of reinforcement should initially be high enough to maintain desired behavior, then decrease gradually

• Inform individual of what schedule you are using

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