fei75766_ch16_495-533.indd 512  02/06/20 01:34 PM
Part VI    Learning-Cognitive Theories512
on the average. Again, training must startwithcontinuous reinforcement, proceed 
toalowresponse number, andthenincrease toahigher rateofresponse. Apigeon 
rewarded every third response ontheaverage canbuild toaVR6schedule, then
VR10,andsoon;butthemean number ofresponses must beincreased gradually 
toprevent extinction. After ahighmean isreached, say,VR500,responses become 
extremely resistant toextinction. (More onrateofextinction inthenextsection.)
Forhumans, playing slotmachines isanexample ofavariable-ratio schedule. 
Themachine issettopayoffatacertain rate,buttheratiomust beflexible, thatis,
variable, toprevent players from predicting payoffs. 
Fixed-Interval   With thefixed-interval schedule, theorganism isreinforced forthe
firstresponse following adesignated period oftime. Forexample, FI5indicates 
thattheorganism isrewarded foritsfirstresponse afterevery 5-minute interval. 
Employees working forsalary orwages approximate afixed-interval schedule. They 
arepaidevery week, every 2weeks, orevery month; butthispayschedule isnot
strictly afixed-interval schedule. Although pigeons typically show aspurt inwork 
toward theendofthetimeperiod, most human workers distribute theirefforts fairly 
evenly rather thanloafing most ofthetimeandthenshowing anend-of-the-period 
spurt. Thissituation isdueinparttosuchfactors aswatchful supervisors, threats 
ofdismissal, promises ofpromotion, orself-generated reinforcers. 
Variable-Interval   Avariable-interval schedule isoneinwhich theorganism isrein-
forced afterthelapse ofrandom orvaried periods oftime. Forexample, VI5means 
thattheorganism isreinforced following random-length intervals thataverage 
Because slotmachines payoffonavariable-ratio schedule, some people become compulsive gamblers. 
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