1Chapter 7 - Operant ConditioningSchedules and Theories ofReinforcementLecture Outline• Schedules of reinforcement–Continuous vs. intermittent schedules–Four basic intermittent schedules– Other simple schedules of reinforcement–Complex schedules of reinforcement• Theories of reinforcement– Drive reduction theory– The Premack principle– Response deprivation hypothesis– Behavioral bliss point approach2Now that we have discussedreinforcement . . . .• It is time to discuss how reinforcements can andshould be delivered• In other words, there are other things to considerthan just what the reinforcer should be.• If you were going to reinforce your puppy forgoing to the bathroom outside, how would you doit?– Would you give him a doggie treat every time? Someof the time?– Would you keep doing it the same way or would youchange your method as you go along?Schedules of Reinforcement•A schedule of reinforcement is the responserequirement that must be met in order to obtainreinforcement.– Each particular kind of reinforcement schedule tends toproduce a particular pattern and rate of performance– In other words, it is what you have to do to get thereward!• Example: Does a dog have to roll over just once to get areward, or does he have to roll over more than once before he’sgiven his reward?3Continuous vs. IntermittentReinforcement• Continuous– A continuous reinforcement schedule (CRF) is one inwhich• Example: every time the dog rolls over he gets a treat every time a child hangs up her coat she gets praised– Useful for strengthening newly learned behaviors orwhen using shaping procedures to train a behavior.– Leads to rapid increases in the rate of the behavior(begins to occur very frequently).– Not very common in a natural environment.Continuous vs. IntermittentReinforcement• Intermittent– An intermittent reinforcement schedule is one in whichonly some responses are reinforced (not everyresponse)• Example: every third time the dog rolls over he getsreinforced.– Useful for maintaining behaviors that are alreadyestablished– They can be based on the number of responses made(ratio) or the time between reinforcement (interval)– They can also be fixed or variable.4Four Basic Types ofIntermittent Schedules• Ratio Schedules-reinforcement givenafter a number ofnon-reinforcedresponses– Fixed Ratio– Variable Ratio• Interval Schedules-reinforcement given for aresponses that occurs aftera certain amount of timehas passed– Fixed Interval– Variable IntervalFixed Ratio Schedule• Fixed ratio schedule (FR) - reinforcement isgiven after a fixed number of nonreinforcedresponses (predictable)– Examples:• FR4 schedule - a salesperson receives a bonus after every 4sales• FR1 schedule - take a break after reading a chapter in the text• FR50 schedule - a rat received a food pellet after every 50 barpresses.• “piecework” - paid by number of pieces sewn together– Schedules can be dense (e.g., FR5) or lean (e.g.,FR100)5Fixed Ratio Schedule• Characteristic pattern:–– Short pause following eachreinforcer• Higher ratio requirements producelonger pauses after reinforcement– e.g., FR50 has longer break beforeresponding again than FR25• Can stretch the reinforcement ratio(e.g., FR1, FR2, FR4, FR6, FR10)• Ratio strain – when requirementincreases too quickly behaviorbecomes erratic or disrupted– Movement from “dense” to “lean”schedules should be donegradually.Variable Ratio Schedule• Variable Ratio (VR): Reinforcer given aftervariable amount of non-reinforced responses (lesspredictable)– VR10 schedule, on average every 10 responses arereinforced but number of responses might vary between1 and 20– Examples• VR6 schedule - a gambling machine pays off every 6 spins onaverage, but payoff trial cannot be predicted• VR50 schedule - a food pellet is dispensed on average every50 bar-presses, but exact trial cannot be predicted• Salesperson working on commission6Variable Ratio Schedule• Characteristic pattern:– High and steady rateof response– Little or no post-reinforcer pausing(every response mightproduce a reward)Other facts about Variable RatioSchedules• Behaviors on this type of schedule tend tobe very persistent– This includes unwanted behaviors like begging,gambling, and being in abusive relationships–“Stretching the ratio” means starting out with avery dense, rich reinforcement schedule andgradually decreasing the amount ofreinforcement• The spouse, gambler, or child who is the “victim”must work harder and harder to get the reinforcer7Four Basic Types ofIntermittent Schedules• Ratio Schedules-reinforcement givenafter a number ofnon-reinforcedresponses– Fixed Ratio– Variable Ratio• Interval Schedules-reinforcement given for aresponses that occurs aftera certain amount of timehas passed– Fixed Interval– Variable IntervalFixed Interval Schedule• Fixed Interval (FI): Reinforcementobtained on first response after a fixed,predictable period of time– Example• FI 2min – a rat receives food on the first lever pressfollowing a 2 minute interval• FI75min - glancing at the clock during class. After75 minute interval, you are rewarded by beingallowed to leave.8Fixed Interval Schedule• Characteristic Pattern:– “scallop pattern” - FIschedules produce anupwardly curved rate ofresponding with increasedrate of responding as theinterval nears its end• Example: study more andmore as a test approaches.– noticeable post-reinforcement pause• Example: don’t study muchafter a test has justoccurred.Variable Interval Schedule• Variable Interval (VI): Reinforcer given for the firstresponse after a varying, unpredictable amount of time– VI 30 sec schedule- on average the first response after every30 seconds is reinforced but the time of reinforcement mightvary between 1 sec & 1 min– Examples• VI 2min - a food pellet is dispensed on the first bar-press following a2 minute interval (on average) but exact time bar-press cannot bepredicted• VI 15min – Hilary’s boyfriend, Michael, gets out of school and turnson his phone some time between 3:00 and 3:30 (the average is after15 minutes) – the “reward” of his answering his phone puts hercalling behavior on a VI schedule, so she calls every few minutesuntil he answers9Variable Interval Schedule• Characteristic Pattern:– Moderate steady rate ofresponse– little or no post-reinforcement