A comparison of fading, non-fading and a combination of procedures in training word recognition with moderately retarded adults.

Transcription

1 University f Massachusetts Amherst SchlarWrks@UMass Amherst Masters Theses February A cmparisn f fading, nn-fading and a cmbinatin f prcedures in training wrd recgnitin with mderately retarded adults. Leslie Ellen Weidenman University f Massachusetts Amherst Fllw this and additinal wrks at: Weidenman, Leslie Ellen, "A cmparisn f fading, nn-fading and a cmbinatin f prcedures in training wrd recgnitin with mderately retarded adults." (1978). Masters Theses February Retrieved frm This thesis is brught t yu fr free and pen access by SchlarWrks@UMass Amherst. It has been accepted fr inclusin in Masters Theses February 2014 by an authrized administratr f SchlarWrks@UMass Amherst. Fr mre infrmatin, please cntact schlarwrks@library.umass.edu.

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3 A COMPARISON OF FADING, NON-FADING AND A COMBINATION OF PROCEDURES IN TRAINING WORD RECOGNITION WITH MODERATELY RETARDED ADULTS A Thesis Presented By Leslie Ellen Weidenman Submitted t the Graduate Schl f the University f Massachusetts in partial fulfillment f the requirements fr the degree f Master f Science May 1978 Department f Psychlgy

4 A COMPARISON OF FADING, NON-FADING AND A COMBINATION OF PROCEDURES IN TRAINING WORD RECOGNITION WITH MODERATELY RETARDED ADULTS A Thesis Presented by Leslie Ellen Weidenman Apprved as t style and cntent by: Beth Sulzer-Azarf f, Chairpersn f Cmmittee Ellen P. Reese, Member A. Jhn W. Dnahe, Member Nrman F. Watt, Department Head Psychlgy Department

5 iii AC KNOWLE DGE ME NTS I wuld like t thank the fllwing peple fr all their assistance in the cmpletin f this prject. the residents f Walters, Kennedy, Hebrn, and Baker drmitries at Mansfield Training Schl fr their participatin as subjects Jack Thaw and Michael Palmer, Psychlgy Department, Mansfield Training Schl fr their general supprt and assistance in lcating subjects Pam Hilpert fr her help in data cllectin Jhn Dnahe, my cmmittee member, fr inspiratin Ellie Reese, my friend, frmer advisr, and cmmittee member fr getting me started in graduate schl, getting me invlved with this prject, and fr her cntinued supprt and valuable cmments Beth Sulzer-Azarff, my friend, advisr, and cmmittee chairman fr her advice, encuragement and cntingencies my sister, Meredith, fr her help in data cllectin and her sympathetic ear.

6 iv TABLE OF CONTENTS INTRODUCTION 1 Early Research in Discriminatin Training... 5 Terrace's Research Prgram in Errrless Learning g Basic Research in Discriminatin Training!!! 12 Transfer f Stimulus Cntrl 24 Applied Research in Discriminatin Training 31 Reversal Training 40 Fading Prcedures 50 Emtinality 58 METHOD 69 Subjects 69 Apparatus 70 Setting 72 Materials 72 Preliminary Training Materials 76 Prcedure 77 RESULTS 84 DISCUSSION 100 Subject Variables 102 Interpretatin f Obtained Data 105 Cmbinatin Training Results 120 REFERENCE NOTES 127 REFERENCES 128 Appendix A 132 Appendix B 138 Appendix C 141 Appendix D 143 Appendix E 148

7 V LIST OF TABLES Table 1. Order f Wrds Trained 78 Table 2. Training Schedule 83 Table 3. Number f Errrs n Prbe Trials by All Subjects in the Fading and Cmbinatin Grups 93 Table 4. Number f Errrs n Secnd Set f Prbe Trials by 3 Subjects in the Fading and Cmbinatin Grups 94 Table 5. The Per Cent f Nn-fading Wrds Mastered Withut Errrs During Training by 5 Subjects in the Nn-fading and Cmbinatin Cnditins 96

8 vi LIST OF FIGURES Figure 1: Apparatus used fr match-t-sample training ~ 71 Figure 2: Percent f crrect trials during training and review fr three cnditins: fading, nn-fading, and cmbinatin training 85 Figure 3: The percent f errr during 15 training trials fr subjects in the fading, nnfading, and cmbinatin cnditins 86 Figure 4: The percent f errr n fading and nnfading wrds by subjects in the cmbinatin training cnditin 86 Figure 5: The ttal number f crrect trials n each wrd trained under fading, nnfading, and cmbinatin cnditins 8 8 Figure 6: The percent f crrect trials per training wrd in fading, nn-fading, and cmbinatin cnditins 88 Figure 7: The percent f crrect trials n retentin tasks fr three training cnditins at fur time intervals 90 Figure 8: The percent f crrect trials n transfer tasks fr three training cnditins at fur time intervals 91 Figure 9: The percent f crrect trials during retentin when training wrds were riginally acquired with and withut errrs 95 Figure 10: The percent f crrect trials n transfer tasks when wrds were riginally acquired with and withut errrs 95

9 vii Figure 11: The percent f crrect trials n retentin tasks fr all fading wrds when riginally acquired with and withut errrs 97 Figure 12: The percent f crrect trials n transfer tasks fr all fading wrds when riginally acquired with and withut errrs 97 Figure 13: The percent f crrect trials n retentin tasks fr all nn-fading wrds when riginally acquired with and withut errrs 98 Figure 14: The percent f crrect trials n transfer tasks fr all nn-fading wrds when riginally acquired with and withut errrs 98

10 , INTRODUCTION When planning a curse, unit, r individualized lessn, a teacher is faced with the task f selecting an apprpriate teaching methd frm amng a variety f available prcedures, sme f which reflect different appraches t educatin. Often, the chsen methd is selected n the basis f cnsideratins that are nt necessarily relevant t the quality f the prgram. Fr example, it is nt uncmmn t find materials used fr reasns such as: They were used befre, they required little additinal preparatin n the part f the teacher r they were the easiest t btain. Teachers familiar with behaviral principles f Educatinal Psychlgy are mre likely t cnsider factrs such as the entering behavir f their students the cmplexity f the behavir t be taught and the cnditins under which the behavir is t be emitted, when chsing a teaching strategy. The behaviral apprach t teaching advcates cnsideratin f these factrs alng with the principles f learning and behavir change. This apprach, which starts with the premise that teaching includes arranging effective instructinal prgrams t meet individual student needs, fcuses teacher attentin n student and curriculum variables and the methds f behavir change. It recmmends that teachers be aware f and prepared

11 . 2 t prvide the apprpriate cnsequences fr student behavirs in a learning situatin. In particular, cntingencies need t be arranged s the desired behavirs will ccur, and be reinfrced when they d ccur. Traditinally, as Skinner (1961) pints ut in his influential article n the imprtance f prgramming and teaching machines, student learning behavirs have been under aversive cntrl. Instead f maintaining this type f system with its undesireable side effects (e.g. avidance, inattentin, mental fatigue) Skinner implres educatrs t rearrange the educatinal envirnments s psitive reinfrcers and nt punishers will fllw apprpriate student behavirs. He demnstrated hw careful prgramming and the use f teaching machines can facilitate learning, and attributed the success f these methds t the fllwing three factrs: 1) reinfrcement ccurs frequently and immediately, 2) students prceed at their natural rates, and 3) the prgram fllws a cherent sequence. He als emphasized the rle f the teacher and stimulus materials is t teach rather than simply t impart" knwledge. This can be accmplished by active student participatin in the learning prcess. Andersn and Faust (1975) labelled this the principle f active respnding. Skinner stated it mre simply, "T acquire the behavir, the student must engage in the behavir" (page 389)

12 3 What types f behavir are invlved in learning in the classrm? Upn examining schl experiences, ne finds that students are asked t define terms, identify examples, slve prblems, synthesize material, evaluate, etc. All these activities can be fund in Blm's taxnmy (1956) r William's typlgy (Nte 8) and can be seen in schl settings. With s many different behavirs and systems f describing them, the task f effective prgramming with active student participatin appears mre cmplex. As a basic student behavir frm which many mre cmplex nes are derived, discriminatin will be examined clsely. The findings frm an intensive investigatin f discriminatin will prvide an imprtant fundatin fr many ther skills. Skinner (1961) discussed the imprtance f discriminatin as a fundamental skill in the fllwing statement. We call an effective persn 'discriminating'. He can tell the difference between the clrs, shapes, and sizes f bjects, he can identify three dimensinal frms seen frm different aspects, he can find patterns cncealed in ther patterns, he can identify pitches, intervals and musical themes and distinguish between different temps and rhythms and all f this in an almst infinite variety. Subtle discriminatins f this srt are as imprtant in science and industry and in everyday life as in identifying the schl f a painter r the perid f a cmpser, (page 381) This emphasis n discriminatin is als seen in the wrk f psychlgists interested in cncept frmatin and the teaching f cncepts. In particular, Eecker, Englemann,

13 4 and Thmas (1976) in their textbk, Teaching 2: Cgnitive Learning and Instructin, teach the reader hw t test fr cncepts. They define a cncept as a critical grup f stimuli that identifies the bject r the idea. Any particular example f a cncept will cntain all the critical features f the cncept as well as many irrelevant features. The jb f the learner is t discriminate thse cases in which all the critical features are present, thus an example f the cncept, frm thse instances in which sme f the critical stimuli are nt present. Jhnsn and Chase (Nte 2) refer t examples in which ne r tw f the critical features are missing as nn-examples f the cncept. Thus it appears that the basic task required f a learner is t discriminate examples frm nn-examples f cncepts. As the educatinal system is cntinually attempting t teach cncepts it seems reasnable t fcus n the literature n discriminatin training in the search fr knwledge pertaining t effective prcedures and methds fr teaching. A search f the literature n discriminatin training reveals a diversity f research frm bth the animal labratries and applied settings. The nature f the research, which naturally reflects the theretical rientatin and interests f the investigatr, may, at first glance, seem far remved frm the basic cncerns f the educatr wh seeks guidelines fr effective teaching. Hwever, the ptential impact f the accumulating bdy f knwledge is

14 5 great. Eventually, with further research, imprtant additinal general principles f teaching will be frmulated as an utcme f this area f study. T date, the impact has been limited, althugh, many prcedures based n experimental findings f discriminatin learning studies are nw being used with special ppulatins and fr training a variety f specific skills. This paper fcuses n the issues in the field f discriminatin training with an emphasis n the develpment f the field, current research directins, and the significance f the findings fr the applied setting. The majr tpics that enter int the discussin include the thery f errrless learning, its impact n training prcedures, fading techniques, and the parameters f a successful fading prgram. Early Research in Discriminatin Training T teach a discriminatin requires that the desired respnse be brught under the cntrl f the psitive, r discriminative, stimulus (S+ r S D ). This prcess can be described as reinfrcing the behavir in the presence f the S+ and extinguishing the same behavir in the presence f the negative stimulus (S- r S A ). Instances f discriminatin learning can be seen in hundreds f everyday situatins. Cnsider the fllwing examples: a student learns t fllw directins after

15 . 6 cmpleting the wrng assignment a sales manager learns t institute an incentive prgram fllwing several years f experiencing an annual pst-hliday sales slump an adult learns when certain cmments are inapprpriate after being ridiculed r ignred. In each case, the learner experienced an unpleasant event which resulted in a change in his behavir. It is likely that under thse same circumstances, thse particular behavirs wuld nt re-ccur. Thrugh cntinued interactin with their wn envirnments, each learner wuld cme t recgnize thse cnditins under which thse behavirs wuld nt be punished. When this has ccurred, ne wuld say that the student, sales manager, r adult had learned a discriminatin and their behavir was under stimulus cntrl The situatins described abve represent examples f the traditinal methd f discriminatin training ften called trial-and-errr. It is bviusly effective, althugh there are disadvantages. Primarily, trial-and-errr implies that the behavir will underg extinctin r sme ther unpleasant cnsequence, befre the crrect pattern f respnding is learned. This feature f respnding in the presence f the S- was at ne time cnsidered essential fr discriminatin learning. When Skinner's (1961) article

16 7 appeared, advcating the use f psitive cntrl in the learning envirnment, researchers began t lk at discriminatin learning frm a new perspective. Skinner argued that errrs did nt prmte ptimal learning in that errrs are ften fllwed by aversive cnsequences which culd prduce emtinal respnses as well as take up learning time. This wuld nt happen in situatins where psitive reinfrcement was used t maximize crrect respnding. Errrs wuld be kept t a minimum thus increasing the prductivity f the learning time. Researchers investigating discriminatin learning began t re-examine the ntin that respnding in the presence f the S- was essential as well as t study the rle f errrs in the training prcess. Wells Hively, ne f Skinner 1 s graduate students, published a paper (1962) in which he demnstrated hw a difficult discriminatin culd be taught t a grup f children withut the use f aversive cntrl and withut many errrs. Hively develped a series f match-tsample tasks f increasing difficulty. Children were seated in frnt f a respnse panel with several respnse keys upn which gemetric patterns culd be displayed. Children were shwn a sample pattern and a rw f chice patterns. The task was t select the pattern that matched the sample by pressing the apprpriate respnse key. The cmplexity f the patterns and f the alternative chices

17 8 increased as the series prgressed. In a sequence f experiments, Hively examined the variables that affected the children's perfrmance n the task f greatest difficulty, called the "criterin task". He recrded the number f errrs made by each subject and fund that the acquisitin f the criterin task was facilitated by arranging a series f prgressively mre difficult discriminatins. He described his sequence as a series f successive apprximatins t the criterin task. One interesting utcme f Hively 1 s experiments was the finding that children wh experienced the criterin task prir t receiving the prgressive training sequence perfrmed prly in cmparisn with children wh received the prgressive sequence withut the prir experience n the criterin task. This result suggested that nt nly were errrs unnecessary fr discriminatin learning but they culd als be detrimental. Terrace's Research Prgram n Errrless Learning Research n the effects f errrs during discriminatin training was als being cnducted in animal labratries. Terrace, (1963a) in his wrk with pigens, develped a systematic prcedure fr teaching discriminatins "errrlessly". The errrless prcedure was quite different frm the traditinal trial-and-errr methd. Trial-and-errr training cnsists f randm presentatins f the

18 9 discriminative stimuli (s+ and S-). Respnding during S+ is reinfrced whereas respnding during S- underges extinctin. As the name implies, t rial-and-errr prcedures result in subjects making many errrs befre the discriminatin is established. In Terrace's errrless prcedure, the subject was similarly presented with the S+ and the S- in a randm rder. Hwever, the initial S- presented was quite different in appearance frm the stimulus that was t serve as the ultimate S- at the end f discriminatin training. The initial stimulus chsen was nt likely t ccasin a respnse frm the subject. As the prgram prgressed, the initial S- was altered gradually until the stimulus appeared in its final frm. This type f prcedure resulted in very few errr respnses t the S-. Terrace's riginal study (1963a) demnstrated the effectiveness f the errrless prcedure in teaching a redgreen clr discriminatin t pigens. The training sequence began with the establishment f a key peck respnse t the S+ (red key). When the subject was respnding reliably, the S- was intrduced. In this study, the initial S- was a dark key which was gradually transfrmed t a green key. The initial S- difference in clr, intensity, and length f presentatin frm the terminal S-. Presenting the dark key fr a brief perid made it likely that the subject

19 10 wuld nt peck the key. Gradually, the green clr was faded in t the equivalent brightness f the red key. Likewise, the length f presentatins was increased t match the S+. Terrace cmpared the perfrmance f birds under fur training cnditins that differed alng the dimensins f 1) an early r late intrductin f the S- fllwing establishment f the key peck respnse, and 2) a prgressive (faded) r cnstant ( trial-and-errr ) presentatin f the S-. The fur experimental grups resulting frm the cmbinatin f the abve dimensins were: - early prgressive - late prgressive - early cnstant - late cnstant The mst interesting result f this study was the superir perfrmance f the subjects in the early-prgressive grup when cmpared with thers. Terrace cncluded that bth an early intrductin and a prgressive presentatin f the S- were essential features f an "errrless" prgram. One explanatin fr the success f the errrless prcedure was that the gradual methd transferred a knwn r easy discriminatin t a mre difficult ne. In the abve example, the initial discriminatin required the subjects t respnd t the red key (S+) and nt t respnd t the dark key (initial S-). This is an easy discriminatin fr pigens as they are nt likely t peck a dark key.

20 . 11 The majr imprtance f the study was that it cnfirmed the belief that a discriminatin culd be learned and learned well withut making errrs. A pst-acquisitin test n the red-green discriminatin fund that the perfrmance f the birds in the early-prgressive grup remained accurate T study this prcedure further, Terrace cnducted a secnd set f experiments in which stimulus cntrl was transferred frm a clr discriminatin t a mre difficult line-tist discriminatin. Again using pigens as subjects, Terrace used the errrless training prcedure t train subjects t discriminate the red and green keys. Then, grup ne was abruptly changed frm the clr stimuli t the hrizntal vertical lines, while the secnd grup had several trials in which the clr stimuli were superimpsed n the line stimuli. A third grup experienced super-impsitin f the clrs alng with a prgressive reductin f the clrs until nly the lines remained. The furth grup received nly vertical-hrizntal training and did nt have any previus experience with clr. All grups learned the line- tilt prblem, hwever, nly the grup that received superimpsitin and fading f stimuli acquired the discriminatin errrlessly. Errrs ccurred in all the ther grups althugh the superimpsitin-nly grup had fewer errrs, indicating that sme transfer

21 . 12 had ccurred. These results clearly shw the advantages f the prgressive technique fr reducing errrs. The final prtin f Terrace's study cnsisted f administering anther set f trials with the clr discriminatin task. Surprisingly, the perfrmances f the different grups varied cnsiderably. Only the birds that had been in the fading cnditin during the line discriminatin training perfrmed perfectly. The thers, wh had made errrs n the line-tilt prblem als made errrs when they were retested n the red-green discriminatin. These results were interpreted t mean that errrs disrupted the perfrmance f a previusly learned prblem. Terrace's findings were similar t thse that had been btained by Hively with yung children. Bth studies demnstrated that discriminatins culd be acquired with few r n errrs. The results als indicated that errrs, instead f being essentail fr discriminatin learning, might in fact have a detrimental affect n already mastered discriminatins Basic Research in Discriminatin Training The fllwing sectin will prvide a discussin f the findings f several basic research prgrams investigating the variables that affect the success f "errrless" r fading prgrams. The term fading, which is ften used interchangeably with the term errrless, refers t the

22 13 gradual change in the stimulus cnditins that ccur during prgramming. It shuld als be pinted ut that the term "errrless" generally refers t a specific criterin f perfrmance that is set (smewhat arbitrarily) by the experimenter. Fr example, in Terrace's wrk (1963a), he defined errrless as. 2 5 r fewer respnses t the S-. As keypecking is a high frequency, lw effrt respnse, 25 pecks des nt represent a significant amunt f pecking. Hwever, sme respnses did ccur in the presence f S-, s errrless shuld nt be interpreted t mean a perfect perfrmance. Such effrts frm the animal labratries make an imprtant cntributin twards increase the understanding f the mechanisms that are invlved in fading fr use in applied settings. The publicatin f Terrace's early studies alng with his chapter n Stimulus Cntrl in Hnig ' s bk Operant Behavir: Areas f Research and Applicatin (1966) stimulated a great deal f research in the field. Terrace essentially believed that learning "errrlessly " was smehw unique. That is, he prpsed that the mechanisms invlved in errrless learning were different than thse underlying trial-and-errr learning. T supprt his thery, he cited as evidence the fact that the behaviral byprducts which ften accmpany traditinal discriminatin training were nt present when the subjects received

23 14 errrless training. Fr example, his subjects did nt exhibit aggressive r emtinal behavirs during S-, nr did they shw behaviral cntrast effects. In additin, there were n shifts in the peaks f generalizatin gradients away frm the value f the S-. Terrace attributed these effects t the errrless prgram. He believed that by eliminating the situatin in which subjects experienced nn-reinfrced respnses t the S-, he had prduced a learning envirnment which wuld facilitate learning withut the accmpanying side-effects. The impact f his wrk can be seen in the numerus studies that fllwed. In fact, a large prtin f the research n discriminatin learning dealt directly with Terrace's ntins. Hwever, nt all investigatrs shared his belief in the unique prducts f errrless learning. Effrts were taken by several researchers t refute Terrace's claims. Specifically, the issue f the behaviral by-prducts f errrless learning was studied. The effrts f many investigatrs revealed a number f prblems with the thery f errrless learning. Additinally, related research in the area detected prblems with the arbitrary nature f the definitin f an errrless perfrmance and the selectin f the measured respnse. T illustrate the prblems with the behaviral byprducts issue, the research n behaviral cntrast will

24 15 be examined. Terrace cntended (n the basis f his wn research) that errrless prcedures did nt ccasin behaviral cntrast. Rilling (1977), in his chapter n Stimulus Cntrl, reprted that he and his students cnducted a series f experiments v/hich demnstrated that the ccurrence f behaviral by-prducts was nt related t the ccurrence f errrs during training. In the case f behaviral cntrast, Kdera and Rilling (1975) replicated the prcedure in Terrace's 1963 study using a slightly different set f discriminative stimuli. Where the S+ and S- had been a red and green key in Terrace's study, Kdera and Rilling used a green key as the S+ and a dark key as the S-. This change in stimuli brught abut a change in the results. Nt nly was errrless acquisitin f the discriminatin achieved in the early-prgressive grup but the ther grups learned errrlessly as well. In additin, behaviral cntrast was bserved in all experimental grups. Slight differences in the degree f cntrast were apparent as a functin f early r late intrductin f the S-. Hwever, after analyzing the data, n direct relatin was fund between the number f errrs and the amunt f behaviral cntrast bserved. Anther issue addressed by Terrace's critics was his ntin f the neutrality f the S- during errrless learning. Terrace (1966b; 1972) maintained that the S- functins

25 16 as an aversive stimulus fllwing learning with errrs whereas it functins as a neutral stimulus fllwing errrless learning. Neutrality was assumed due t the lack f emtinal and aggressive behavirs emitted by subjects in the errrless cnditins. Subjects in the errr (r traditinal) grups were bserved t emit emtinal behavirs such as wing flapping and aggressive behavirs twards the key when the S- was present. Tw explanatins have been ffered fr the ccurrence f emtinal and aggressive behavirs. Terrace prpsed that aggressin is prduced by the "frustratin that ccurs as a by-prduct f nn-reinfrced trials". Rilling, n the ther hand, suggests that the withdrav/al f the pprtunity fr reinfrcement is the cause. Research specifically cncerned with the ccurrence f aggressive behavirs was cnducted in an attempt t clarify the situatin. Rilling and Caplan (1973) trained pigens t discriminate between a green key (S+) and a dark key (S-) using an errrless prcedure. In additin, they prvided a target bird in the experimental chamber which set the ccassin fr aggressive and attack behavirs. The rate f attack during each stimulus cnditin was recrded thrughut discriminatin training. The results shwed a rate f attack significantly higher than the perant level fr all subjects regardless f the training prcedure and

26 17 the resultant errrless acquisitin f the discriminatin by all subjects. These data cannt accmmdate Terrace's assertin that aggressin is the utcme f nn-reinfrced respnses t the 3- but d lend supprt t Rillings ntin that the withdrawal f the pprtunity fr reinfrcement is the crucial variable in determining whether r nt aggressive behavir will ccur. In additin t the investigatin f aggressin, Rilling and his clleagues examined the questin f neutrality f the S- by directly measuring the aversive quality f the S- during discriminatin training. First, Rilling, Askew, Ahlskg, and Kramer (1969) established a successive discriminatin r "escape prcedure" as a valid indicatr f the aversiveness f the S-. The successive discriminatin prcedure invlved tw respnse keys and a pair f discriminative stimuli. Apprpriate respnding t the S+ and the S- was established n the first key. Respnses t the secnd key resulted in a "time-ut" r terminatin f the stimulus appearing n the first key and a 5-secnd darkening f the chamber. During traditinal discriminatin training, Rilling et al, fund that respnses t the secnd key were mre frequent during S- than S+. This finding, Rilling nted, was cnsistent with Azrin, Hutchinsn and Hake's (1966) study and Rilling and Caplan's (1973) wrk n aggressin and supprted the ntin that the

27 18 subjects* respnding t prduce "time-ut" was an index f the aversiveness f the S-. With the validatin f the prcedure, Rilling, Kramer and Richards, (197 3) applied the technique t an errrless discriminatin t test Skinner's assertin that errrs are aversive and a learner will escape r avid a situatin in which errrs have ccurred. Varying the dimensins f 1) early r late intrductin f the S-, and 2) a prgressive r cnstant presentatin f the S- (mdelled after Terrace's 1963a study) fur experimental grups were studied. Training which cnsisted f a red-green clr discriminatin, and the pprtunity fr escaping S- was available fr each grup. The results f the discriminatin training replicated Terrace's findings in which the subjects in the prgressive grups made the fewest errrs. The effect f the dimensins f the training prcedure n the number f time-uts whwed that the time dimensin (early r late intrductin f the S-) had a greater effect than the methd f presentatin (prgressive r cnstant). Subjects in bth the late-cnstant and late-prgressive grups emitted many mre escape (time-ut) respnses than the early grups. Rilling cncluded that the number f respnses made t the S- was a pr predictr f the number f time-uts r escape respnses. The significance f this finding, accrding t Rilling, is that it fails t supprt Terrace's ntins cncerning the aversive prperties f

28 : 19 the S-. He summarizes his cnclusin in the fllwing statement T the extent that time-uts frm S- are an index f the aversive prperties f S-, these data d nt supprt the view that the aversiveness f a stimulus is directly prprtinal t the number f unreinfrced respnses emitted in its presence, (page 470) Other investigatrs shwed that the use f a prgressive technique as riginally utlined by Terrace is nt necessary t prduce an errrless perfrmance. Wessells (1974) fr example, btained an "errrless" perfrmance in an autshaping experiment with pigens. Autshaping refers t a prcedure in which the experimenter des nt directly shape the subject's respnse. In the Wessells study, a discriminatin between a green key (S+) and a white vertical line (S-) was trained in the fllwing manner. The S+ was illuminated fr 6-secnds and immediately fllwed by reinfrcement regardless f the bird's behavir. The white line (S-) was illuminated and never fllwed by reinfrcement. Pecking emerged during the presentatin f the S+. The pigens learned t discriminate the S+ frm the S- withut pecking the S-. Thrughut the study, Wessells recrded tw pre-pecking respnses, rientatin and apprach t the respnse key, in additin t the number f pecking respnses. He fund that the rate f these behavirs increased and decreased during S+ and S- respectively as the autshaping prgressed until, essentially n respnses

29 20 were emitted during S-. The results f Wessell's study raise the questin f the validity f the definitin f errrless learning. In restricting the definitin f an errrless perfrmance t the nnccurrence f a particular respnse, ne shuld remember the respnse may be the terminal pint in a chain f behavir. As Wessell demnstrated, bth rientatin and apprach t the respnse key are imprtant links in pecking respnse chain. By recrding the frequency f these pre-pecking behavirs, he has shwn that 1) they d ccur within the "errrless" prcedure, and 2) they cme under the cntrl f the discriminative stimuli as the key-peck itself des. It des nt seem realistic t assume that different mechanisms f learning culd accunt fr the develpment f stimulus cntrl f tw prtins f the same respnse chain. In Wessell's study, nly the key pecking respnse culd be said t have been acquired errrlessly accrding t Terrace's definitin. If ne accepts the errrless premise then the rientatin and apprach respnses wuld have t have cme under stimulus cntrl by means f the trial-and-errr prcedure. Anther prblem encuntered in a discussin f errrless learning is that it is nt always clear that the distinctin has been made between utcme (i.e. n respnses t the S-) and prcedure (prgressive methds r fading

30 21 techniques). Errrless learning refers t the utcme whereas errrless training refers t the prcedure. The use f "errrless" in bth instances can lead t cnfusin as it is cnceivable (and actual) that an errrless prcedure might nt result in errrless learning. As has been nted, the criteria fr an errrless perfrmance is selected arbitrarily, and as Wessells has demnstrated, the respnse measured may be arbitrary as well. Sme f the research cnducted n the specific behaviral by-prducts f discriminatin training has pinted ut that the training prcedure (prgressive r abrupt intrductin f the S-) may nt have any relevance t the number f errrs made by the subjects in the prgram. The prblem with the dual usage f the term "errrless" is that it may fail t cnvey the apprpriate meaning. Therefre, it seems that its usefulness as a descriptr f a bdy f research is limited and perhaps shuld be replaced by less ambiguus terms (eg. fading) where meaning is restricted t the prcedure r the utcme but nt bth. Frm the evidence described, it seems clear that errrless learning is nt the special prcess that Terrace believed it t be. His thery is unable t accunt fr all the available data and needs t be re-examined, perhaps refrmulated, r discarded. Rilling emphasizes this pint in his chapter and suggests that researchers might prfit

31 22 frm appraching the prblem f errrless learning and fading prcedures frm the pint f view f stimulus cntrl. This wuld enable investigatrs t determine the variables that affect the rate f respnse t the S- which in turn wuld prvide valuable infrmatin fr prgrammers interested in engineering systems fr applied settings. The majr variables that have prven t be imprtant can be categrized as prcedural and physical. Bth Terrace and Rilling have islated tw distinct prcedural variables. They are: (1) the time in the subject's experimental histry that the S- is intrduced, and (2) the rapidity with which the S- is intrduced. The imprtance f bth variables can be seen in the develpment f fading prcedures and in the riginal wrk n errrless learning. Fr example, in Terrace's 1963 studies, an early prgressive intrductin f the S- resulted in the least number f errrs. Bth prcedural variables were manipulated in Terrace's wrk, and nw, it appears that bth have cntributed t the cntrl f the errr respnses. Once the variables have been identified, the next task is t determine the degree f stimulus cntrl exerted by them. Fr the prcedural variables, ne determinant that has been identified is the physical similarity f the discriminative stimuli. Whether r nt the S+ and the S- differ n an inter- r an intra-dimensinal basis has been fund

32 23 t be a gd predictr f the number f respnses that ccur during S- in a traditinal discriminatin prcedure. Kdera and Rilling (1975) cnducted a study with pigens and examined the effects f using intradimensinal discriminative stimuli and cmpared the results with interdimensinal training. The sets f stimuli used were a green key (S+) and a dark key (S-) fr the interdimensinal set, and a green key (S+) and a red key (S-) as the intradimensinal pair. In a statement summarizing the results f his wrk and ther investigatins n the effects f stimulus similarity, Rilling cncluded that interdimensinal training prduces fewer errrs than intradimensinal training primarily because f the dissimilarity f the stimuli. T reduce the likelihd f errrs in the case f intradimensinal training, fading prcedures can be emplyed. By definitin, the changes in the stimulus wuld be gradual which wuld imprve the chances f success. Based n the actual evidence amassed s far n the effects f different prcedural variables, fading prcedures seem like a viable slutin t sme f the prblems encuntered in training difficult discriminatins in applied settings. What the effects f fading wuld be in an interdimensinal discriminatin are less apparent. The parameters f fading need t be studied further in rder t understand the limitatins f the prcedure. Rilling (1977) addresses this issue in the fllwing statement:

33 24 Regrettably, fading remains a part f the art rather than the science f perant cnditining... The parameters f fading which are necessary fr errrless learning remain uninvestigated. Hw rapidly shuld the intensity and duratin f the S- be increased t btain ptimal errrless learning? Furthermre, the effectiveness f fading is rarely cmpared with apprpriate cntrl cnditins in which fading is nt emplyed, (page 466) Transfer f Stimulus Cntrl In additin t the emphasis n errr reductin that results frm the applicatin f fading prcedures, fading is interesting frm the pint f view f transfer f stimulus cntrl. Fading techniques prvide a means f shifting stimulus cntrl frm ne set f discriminative stimuli t anther. Generally, when the variables are arranged prperly, subjects in fading prgrams make relatively few errrs, which is usually the gal f the designer f the fading prgram. Althugh applied research prgrams use fading techniques t transfer stimulus cntrl frm ne set f discriminative stimuli t anther, the research emphasis fr the mst part has fcused n the subjects' acquisitin f the target discriminatin rather than n the changes in stimulus cntrl that accmpany the varius stages in the fading prgram. The fact that fading can facilitate the change in stimulus cntrl frm ne set f discriminative stimuli t anther is particularly interesting when cnsideratin is given t the results f anther prcedure used in animal

34 .. 25 learning studies that is analgus t fading. The prcedure invlves training subjects t respnd simultaneusly t cmpund sets f discriminative stimuli (thus the term simultaneus cmpund cnditining). The stimulus cntrl exerted by the cmpnents f the cmpund is effected by prir experience with the stimuli. Impaired stimulus cntrl has been reprted when a training sequence, similar in sme respects t the fading prcedure, has been used. This reductin in the degree f stimulus cntrl acquired by the stimulus cmpnents has been termed "blcking" Blcking has been demnstrated bth in classical cnditining paradigms (Kamin, 1969) and recently within an instrumental paradigm (Dnahe, 1977) A blcking design can be described as a three phase experimental prcedure which can be diagrammed as fllws: Phase 1 Phase 2 Phase 3 Experimental A, B AC, BD C,D Grup Cntrl AC, BD C,D Grup In phase 1, subjects are trained t respnd differentially t a set f stimuli, A and B. In phase 2, additinal stimuli C and D are added t the riginal set thus prducing a pair f cmpund stimuli, AC and BD. The third phase cnsists f a generalizatin test fr the stimulus cntrl acquired by the cmpnents C and D. A cmparisn f the

35 26 results f the generalizatin test (phase 3) f the experimental grup and the cntrl grup indicates whether r nt blcking has ccurred. If the acquisitin f stimulus cntrl has been blcked, the generalizatin gradients f the experimental subjects will be flatter and less prnunced than the gradients f the cntrl subjects. The subjects in Dnahe 1 s 1977 study were pigens and the respnse was a keypeck. The discriminative stimuli cnsisted f tw line angles, in phase 1, t which tw different wavelengths f light were superimpsed in phase 2. The testing cnditins in phase 3 cnsisted f a generalizatin test ver a range f wavelengths. The results indicated that cntrl f respnding by the wavelengths f light was weaker fr subjects in the experimental grup than in the cntrl grup. That is, the acquisitin f stimulus cntrl was "blcked" by the phase 1 cnditining with the line angle stimuli. The relevance f these findings t fading shuld be clear if the blcking design is regarded as anther methd f transferring stimuls cntrl frm ne set f stimuli (A, B) t anther (C,D) thrugh a prcess f simultaneus cmpund cnditining (AC,BD). Essentially, the fading prcedure which emplys a prgressive change in stimuli has seemed t successfully accmplish what the blcking design seems t inhibit. Hwever, it shuld be kept in mind that the weakened stimulus cntrl

36 27 reprted in the blcking studies refers t the relatin between the level f cntrl in the experimental and cntrl grups. Withut an equivalent cmparisn grup fr the fading studies, where cntrl grups received prir experience with cmpnents f the cmpund stimuli (eg. phase 1 f blcking design), it is difficult t specify the degree t which ne prcedure inhibits and the ther facilitates the transfer f stimulus cntrl. One study cncerned with the degree f stimulus cntrl exerted by the cmpnents f the stimuli used in a fading prgram was cnducted by Fields, Brun, and Keller (197 6). They designed a prcedure using cmpund discriminative stimuli and prbe trials that permitted mnitring f stimulus cntrl f all cmpnents during the entire fading prgram. Fields, Brun, and Keller trained pigens t differentially respnd t a red (S+) and black (S-) key. A fading prcedure was used t transfer stimulus cntrl t the white lines that differed in rientatin by 90". the lines were gradually faded in until they appeared at full intensity n the respnse key alng with the clr stimuli. This was fllwed by the gradual remval f the clr cmpnents which cmpleted the transfer f stimulus cntrl t the line stimuli. Thrughut training, prbe trials cnsisting f independent presentatins f each cmpnent and the cmpund stimuli were presented. The

37 : 28 degree f respnding t the prbes prvided a measure f the stimulus cntrl achieved by each f the cmpnents. The results shwed that during the initial fading in f the lines, nly the clr stimuli cntrlled respnding. When the cmpund prbes were presented, respnding ccurred but t a lesser degree than t the clrs alne, indicating that respnding was cntrlled entirely by the clr stimuli. During the early stages f the remval f the red stimulus, respnding t red was greater than t either the cmpund stimulus r the lines. As fading cntinued, the cmpund stimuli gained greater cntrl and eventually, when the red was nearly faded, the line stimuli achieved cntrl t the apprximate level f the cmpunt S+. They als reprted that reintrducing the clr stimuli resulted in apprpriate respnding and cntrl by the clrs. This indicates that cntrl by the clr stimuli was nt lst in the transfer f stimulus cntrl frm clr t line stimuli. What the authrs cnsider the mst significant utcme f this study is that it cnfirms a previusly suggested ntin that new stimuli presented in a fading prgram acquire stimulus cntrl in tw stages. T explain the tw stage prcess, the authrs turned t the blcking paradigm. Blcking, accrding t Fields, Brun and Keller, means

38 ). 29 previus discriminatin training with ne set f stimulus elements fund in cmpund stimuli reduces the cntrl acquired by the ther elements f the cmpund stimuli, (page 299) They als pint ut hw the blcking design relates t the acquisitin f stimulus cntrl in fading in the fllwing statement. In fading experiments where the intensity f the riginal (blcking) stimuli systematically decreases, the blcking effects might be expected t decrease as fading prgresses and the new stimuli shuld acquire cntrl f respnding This, in fact, is what happened, and in an errrless fashin. Stimulus fading, then, can be cnceptualized as a prcedure by which a thrughly blcked stimulus dimensin acquires cntrl f respnding in an errrless fashin due t the gradual eliminatin f the riginal blcking stimuli. (page 299 They further suggest that the parameters that affect r reduce the likelihd f blcking shuld in turn enhance the effectiveness f a fading prcedure when applied t the riginal stimuli. Such a ntin is appealing yet remains t be empirically demnstrated. Althugh sme f the parameters in questin still need t be identified, the blcking design prvides a theretical framewrk which may further the understanding f fading as well as prvide a directin fr future research. Fr example, by viewing the prblem f transfer f stimulus cntrl as a cntinuum with fading r facilitated transfer at ne end and blcking r impaired transfer at the ther, ne can direct the search fr cntrlling variables t thse that wuld affect

39 30 mvement alng the cntinuum. This view f fading eliminates the apparent cntradictin f utcmes f fading and blcking. Hwever, the identificatin f the cntrlling variables is still imcmplete. Once determined, they wuld allw fr systematic variatin t prduce varying degrees f blcking r transfer f stimulus cntrl in specific training prgrams. As has been discussed, it appears that when and hw the S- is intrduced, as well as the physical dimensins f the stimuli are imprtant variables in determining the rate f acquisitin f a discriminatin. Hw these particular variables interact v/ith each ther wuld als need t be evaluated if a cmprehensive accunt f stimulus cntrl is t be achieved. In spite f the lack f a cmplete understanding f the cntrlling variables invlved in fading, the prcedures have been widely used with a variety f respnses and subject ppulatins. The many studies that appear in the literature have reprted varying degrees f success in discriminatin learning with minimal errrs. Perhaps when the parameters have been identified, the results f many studies can be re-examined and explained. Until that time, attempts t islate the imprtant features will cntinue as the use f fading prcedures cntinues. It seems that a majr prblem cnfrnting applied researchers which prevents a ttally systematic apprach t identifying parameters

40 . 31 is that the immediate needs f clients and available resurces ften direct the curse f the investigatins. Hwever, cmmnalities can be fund amng the features f the reprted studies frm which the imprtance f particular variables can be inferred. Once the variables have been islated in this manner, they can then be subjected t a cmplete experimental analysis The fllwing sectins f this paper will be devted t a discussin f the applied research in the areas f fading and "errrless" learning. The riginal applied studies f fading grew frm attempts t test Terrace's ntins n errrless training. Later studies fcused n an investigatin f sme f the effects f errrless training n retentin and transfer f the learned discriminatins using a variety f ppulatins. Thrughut the discussin, reference will be made t cncurrent studies cnducted in the animal labs which ften prvided the impetus fr the applied research. Applied Research in Discriminatin Training In 1964, Mre and Gldiamnd reprted an early study n errrless discriminatin using Terrace's prcedures with human subjects. They trained a frm discriminatin with pre-schlers using a delayed match-t-sample frmat. In a delayed match- t-sample prcedure, the subject is shwn a sample fr a few secnds after which it is remved frm

41 . 32 view. A rw f chice stimuli are then presented (ne f which is identical t the sample), and the subject is asked t chse the ne that is the same as the sample. Tw series f stimuli were develped, a faded series and a full presentatin. The faded series transferred stimulus cntrl frm a brightness dimensin t a frm dimensin whereas the full presentatin represented a cntrl prcedure with all the stimuli at full intensity. In the fading series, the crrect chice was always at full intensity. The incrrect chices were initially dark and intensity was gradually increased as the prgram prgressed. The experimenters varied the pint at which the fading series was intrduced and terminated fr each f the six subjects. This enabled them t examine several variables such as the effect f prir training with full intensity n perfrmance, the dependence n the irrelevant cue f brightness, and the need fr fading in rder t acquire the discriminatin Fr all subjects, the fading prcedure was necessary t achieve perfrmance at greater than chance levels. The subjects wh received predminately faded training made fewer errrs and established the discriminatin in less time than thse wh were trained primarily with the full series. Examinatin f individual data revealed that mst subjects were dependent n the brightness cue until very

42 late in the series and that perfrmance was disrupted by intrducing the criterin series befre fading was cmpleted. In sme cases, after the intrductin f the full series, backtracking n previusly mastered fading trials was necessary befre accuracy was restred. This study clearly demnstrated ne f the advantages f using a fading prcedure which cnsequently affected its ppularity. It was mre effective in teaching a discriminatin than the traditinal trial-and-errr methds and it succeeded in a case where the ther methd failed. The usefulness f errrless prcedures was shwn in several studies by Sidman and Stddard (1967), Stddard and Sidman (1967), and Tuchette (1968) with severely and prfundly retarded bys, a ppulatin f subjects generally regarded as unable t learn. Using the ratinale that errrs are the prducts f the teaching methdlgy (Skinner, 1961) and prcedures that eliminate errrs frm the learning prcess make learning easier fr thse wh riginally had difficulty, Sidman and Stddard develped a fading prgram t teach a circle-ellipse discriminatin. In the Sidman and Stddard study, stimuli were presented n the uter eight keys f a nine key matrix. The subject's task was t select the circle frm the ellipses by pressing the crrect key. The first grup f subjects, the Prgram Grup, received a fading sequence cnsisting f

43 .. 34 backgrund fading fllwed by ellipse fading. A back-up prcedure was in effect where an errr n any trial result* in the representatin f the preceding array f stimuli. The secnd grup, the Test Grup, received cnventinal trial and errr training that cnsisted f tw cmpnents First, the subjects were presented with the circle-ellipse prblem. If a subject did nt master the discriminatin, he was presented with a frm-n frm discriminatin als in the cnventinal fashin and then re-tested n the circle-ellipse The results shwed that 7 ut f 10 children in the Prgram Grup learned the discriminatin althught nt withut making mistakes. In the Test Grup, nly ne subject mastered the discriminatin with the first presentatin f the circle-ellipse stimuli. Of the remaining 8 subjects wh received the frm-n frm test, 6 were able t master it but nly 3 were able t acquire the circleellipse discriminatin n the secnd presentatin. In the verall analysis f the data, the subjects in the fading grup established the discriminatin in less time and with fewer errrs than the test grup subjects. This study is interesting as it demnstrates again that fading prcedures can succeed where trial-and-errr training cannt. In additin, it pints ut that ther factrs besides a slw, gradual intrductin f the S- can

44 35 effect the utcme f training (i.e. whether r nt errrless acquisitin is achieved). A training prgram, with many alternative chices may ccassin errrs in the fading prgram. Sidman and Stddard carefully examined the errrs emitted by their subjects and fund that imperfectins in bth the arrangement f cntingencies and in the use f a back-up prcedure ften resulted in reinfrced errr patterns which interferred with the subjects' ability t learn the apprpriate respnse. In a fllw up study, Stddard and Sidman (1967) investigated the effects f errrs n children's perfrmance n the circle-ellipse discriminatin. Using a prcedure t establish threshlds f circle-ellipse differentiatin, they designed ne prgram t generate errrs and ne prgram t reduce the prbability f errrs. In the first phase f the experiment, all the subjects were given the riginal circle-ellipse discriminatin prgram. In the secnd phase, the cntrl grup cntinued thrugh the fading prgram until their detectin threshlds were reached. The experimental grup was advanced t the last stage f the prgram where the circle was virtually indistinguishable frm the ellipse but with each errr the prgram backed-up ne step thus making the discriminatin slightly easier. When the child culd reliably select the circle that stage became the reverse rder threshld. Once this threshld