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 be 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 are 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 • Produce high rate of 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. • Also 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 FR • VR produces higher resistance to extinction that FR of same value
Simple Interval Schedules • Schedules are based in time • Fixed-Interval (FI) Schedule • The first response after a fixed amount of time following previous reinforcement is reinforced; 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
Simple Interval Schedules • 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 • 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 Schedules with Limited Hold • Finite time after a reinforcer becomes available that a response will produce it. • FI/LH • VI/LH Reinforcement in interval No Reinforcement No Reinforcement First Response Reinforced
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 want ratio-like behavior, 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
Concurrent Schedules of Reinforcement • Schedules of reinforcement that are in effect at any given time • Herrnstein (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
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.