1977), (Nel- - Illinois State University Websites et... · journal oftheexperimental analysis of...

JOURNAL OF THE EXPERIMENTAL ANALYSIS OF BEHAVIOR

EQUIVALENCE CLASS FORMATION IN LANGUAGE-ABLEAND LANGUAGE-DISABLED CHILDREN

JEANNE M. DEVANY, STEVEN C. HAYES, AND ROSEMERY O. NELSON

AUBURN UNIVERSITY, UNIVERSITY OF NEVADA-RENO, ANDUNIVERSITY OF NORTH CAROLINA-GREENSBORO

Stimulus equivalence seems to have relevance to the study of semantics and of language more gen-erally. If so, there may be a relation between language use and the demonstration of stimulus equiv-alence. This was examined in three groups of children ranging in chronological age and matched ona conventional measure of mental age: normally developing preschoolers, retarded children who usedspeech or signs spontaneously and appropriately, and retarded children who did not. All childrenwere taught a series of four related discriminations and were then tested to determine if classes ofequivalent stimuli had formed. All of the language-able children (retarded and normal) formedequivalence classes, whereas none of the language-disabled children did so. Although the exact natureof the relation between stimulus equivalence and language remains to be clarified, these results supportthe view that stimulus equivalence is a phenomenon with relevance to language.Key words: stimulus equivalence, conditional discrimination, language, verbal behavior, children

In traditional views of language, much ismade of the symbolic nature of words, butrelatively little work has been done to showwhy or how words come to function as sym-bols. Instead, the literature has asserted thatwords do act as symbols and has traced theiruse. Verbal humans are said to be able to"manipulate symbols" (Clark & Clark, 1977),to "map words onto internal concepts" (Nel-son, 1974), or to use words to "refer" to ob-jects, events, or relations (Premack, 1976).Exactly what constitutes a symbol and whatgives rise to symbolic relations in verbal hu-mans is rarely addressed. For instance, thetextbook quoted above by Clark and Clarkrepeatedly refers to the symbolic nature oflanguage, but fails even to include the word"symbol" in its index. It is as if the origin ornature of symbolic activity per se need not beexplained.

Behavioral perspectives should be well po-sitioned philosophically to address the ontog-eny of symbolic relations. Previous views of

The authors wish to thank the staff and students of theHenry Wiseman Kendall Center and the University ofNorth Carolina-Greensboro Child Care Education Cen-ter, especially Joan Moran and Pieter VanIderstine, fortheir cooperation and support of this project. Special thanksare also extended to Rick Cook, who collected all of thereliability data and to Murray Sidman and Aaron Brown-stein for their helpful comments. Requests for reprintsshould be addressed to Jeanne M. Devany, Departmentof Psychology, Auburn University, Alabama 36849-3501.

the nature of meaning, however, have re-stricted the scope of behavior-analytic inves-tigation. From a Skinnerian viewpoint, the"meaning" of a word to a listener is estab-lished through direct contingencies embeddedin interactions with the verbal community(Skinner, 1957). The symbolic meaning of thearbitrary vocal stimulus "bread," for exam-ple, is found through observation of the be-havior it occasions, based on the direct contin-gencies of reinforcement in which itparticipates. Other than the fact that thesecontingencies are largely social, the meaningof a word is thought to be established in amanner functionally identical to stimulus-control processes readily seen in infrahumans.From the standpoint of the listener, this anal-ysis essentially views symbols as discrimina-tive stimuli and not of special interest in theirown right.

Symbols used by humans, however, appearto be much more flexible than discriminativestimuli as typically conceived. For example,in a Quebecois human child, the English writ-ten word "bread" or the French written word"pain," their spoken counterparts, pictures ofbread, and loaves of bread all enter into a richnetwork of relations in which each may (in asense) stand for the others. This seems to bea defining property of symbols and is consis-tent with the word's etymology. The word"symbol" comes from root words meaning"together" and "to throw." Symbols, then, are

243

1986, 469 243-257 NUMBER 3 (NOVEMBER)

JEANNE M. DEVANY et al.

stimuli that are "thrown together" with otherstimuli. The relation between a symbol and areferent seems necessarily bi-directional. Aword "stands for" another event only if theevent "is called" the word.

There is one behavioral process, stimulusequivalence, that appears to relate quite closelyto the issue of symbolic activity (Sidman &Tailby, 1982). When humans are taught aseries of related conditional discriminations,the component stimuli of the discriminationsoften become related to each other in new waysthat had not been explicitly taught in training(e.g., Sidman, Cresson, & Willson-Morris,1974). For example, if a child is taught tomatch A to B and then A to C, it is likely thatthe child will, without additional training, beable to match B to A and C to A and, perhapsmost importantly, match B to C.We speak of an equivalence class if the

stimuli in the class show the three definingrelations of reflexivity, symmetry, and tran-sitivity (Sidman & Tailby, 1982). In match-ing-to-sample procedures, reflexivity is gen-eralized identity matching-matching a novelstimulus to itself under conditions of no re-inforcement. That is, if an organism is pre-sented with bread, it will select bread from anarray of items even in the absence of pro-grammed reinforcement of that choice. Sym-metry refers to the functional reversibility ofthe conditional relation: if A, then B; and ifB, then A. In the presence of the printed wordBREAD, a loaf of bread is selected; and, inthe presence of a loaf of bread, the printedword BREAD is selected. This reversibilitymust be demonstrated in the absence of directreinforcement to be considered symmetry(Sidman, Rauzin, Lazar, Cunningham,Tailby, & Carrigan, 1982). To demonstratetransitivity, at least three stimuli are required.If after the relations "if A, then B" and "if B,then C" have been taught, the relation "if Athen C" emerges without additional training,transitivity has been demonstrated. For ex-ample, if the child has been taught to selectbread upon hearing "bread" and to select theprinted word BREAD upon seeing bread,when the child selects BREAD upon hearing"bread," without any additional teaching, thentransitivity has been demonstrated.

In the context of stimulus equivalence, a"symbol" and its "referents" form a class offunctionally substitutable elements. The re-

lation between a symbol and its referent is nota unidirectional conditional relation (althoughthe members of the class are conditionally re-lated to each other); the relation is function-ally reversible. The relations among the mem-bers of an equivalence class appear toapproximate what psycholinguists and othersmean when they say that a word representsor "stands for" its referent in a way that aconditionally related response does not.

If equivalence classes have to do with verbalor symbolic activity, and if symbolic stimulidiffer from more typical forms of discrimina-tive stimuli, we would expect that it would beeasy to demonstrate the formation of equiva-lence classes with humans and difficult to doso with nonhumans. This is exactly what hasbeen found in the research done to date. Theformation of classes of equivalent stimuli hasbeen demonstrated using a wide variety of hu-man subjects and materials (Dixon, 1976;Dixon & Spradlin, 1976; Gast, VanBiervliet,& Spradlin, 1979; Mackay & Sidman, 1984;Sidman, 1971; Sidman et al., 1974; Sidman& Tailby, 1982; Spradlin, Cotter, & Baxley,1973; Spradlin & Dixon, 1976; VanBiervliet,1977; Wetherby, Karlan, & Spradlin, 1983).Although conditional relations have beendemonstrated in a variety of infrahumans, in-cluding dolphins (e.g., Herman & Thompson,1982), rats (e.g., Lashley, 1938), pigeons (e.g.,Edwards, Jagielo, & Zentall, 1983), andmonkeys (e.g., Nissen, 1951), these relationshave not yet been shown to result in stimulusequivalence as they do in most humans. Todate, there has been no success in unequivo-cally demonstrating the formation of anequivalence class in any infrahuman, includ-ing the higher primates, although efforts havebeen made (Sidman et al., 1982). Further, re-searchers have had considerable difficultydemonstrating transitive transfer in chimpan-zees and other infrahumans even under con-ditions of direct reinforcement (Fouts, Chown,& Goodin, 1976; Kendall, 1983).A type of "transitive" responding has re-

cently been demonstrated in monkeys (D'A-mato, Salmon, Loukas, & Tomie, 1985), butit did not require symmetrical responding.This clearly distinguishes it from stimulusequivalence as currently defined, and maymake their results more amenable to directconditioning explanations. Similarly, verycomplex classes of stimuli can be established

244

STIMULUS EQUIVALENCE AND LANGUAGE

in chimpanzees (Savage-Rumbaugh, 1984),but no direct tests of symmetry or transitivityhave been done to see if these classes functionas equivalence classes (Savage-Rumbaugh,personal communication, May 1985). Thesevarious findings suggest that the ability to formequivalence classes is related to language de-velopment, not because language and stimulusequivalence both do not occur in infrahu-mans-with proper training they may-butbecause both are known to occur with relativeease in most humans, and are at least difficultto show in infrahumans.

Thus, the relations seen among stimuli inan equivalence class seem to parallel the sym-bolic relations commonly said to be character-istic of language. If so, the ability to formequivalence classes should be related to lan-guage acquisition or use; however, no exper-iments relating language use and equivalenceclasses have yet been published. One approachto the problem is to compare the performancesof normally developing children with the per-formances of language-impaired children onan equivalence test. If the normally develop-ing children were able to form equivalenceclasses and the language-deficient childrenwere not, the data would provide further sup-port for the view that the ability to form classesof equivalent stimuli is related to language.Additional research could begin to address theprecise nature of that relation.The present project addressed the question:

Is there a difference between normal and lan-guage-deficient children in performance ontests of equivalence? Three groups of childrenwere used: normally developing children, re-tarded children demonstrating some expres-sive speech, and retarded language-deficientchildren. The three groups were matched withrespect to conventional measures of mental age.Each of the children was taught a series ofconditional discriminations and was subse-quently tested to determine if an equivalenceclass had formed.

METHODSubjects and Subject Identification

Twelve children, four in each group, whosemeasures of mental age ranged from 14 to 36months, served as subjects. The first groupconsisted of normally developing preschoolers

recruited from the UNC-G Child Care Cen-ter. The second and third groups were com-posed of retarded children. All of these chil-dren were enrolled in educational programsat the Henry Wiseman Kendall Center inGreensboro.

All of the normally developing preschoolershad speech skills that were generally consis-tent with their chronological ages. No formalassessment of their speech and language skillswas done; however, in the training and testingsessions no abnormalities of speech or lan-guage were noted. In addition, no abnormal-ities were noted by the classroom teacher, norwere any observed during in-class observationby the experimenter.

Half of the retarded children engaged inspeech outside of language-training sessions.All of these children spoke in complete, albeitbrief, sentences when prompted and oftenspontaneously asked for desired items or com-mented on events in the classroom. Two ofthese children had articulation problems,however (Carl and Allen, names changed toprotect confidentiality). The other retardedchildren lacked functional speech or languageskills. None of these children spontaneouslyused words, signs, or picture boards. Two ofthe children were echolalic, repeating wordsor phrases without evidence of comprehension(Debbie and Andrew), and two of them ut-tered vowel sounds (Craig and Barb).The retarded children were classed into

language and no-language groups on the basisof converging categorization from three inde-pendent observers. The speech pathologist atthe retarded children's institution was askedto categorize all of the children in two pre-school classes into one of two categories: pos-sessing functional speech or sign skills (usedin communication, even if poorly articulated),or as lacking functional speech or sign skills.This was done before the study began. Shewas not told the purpose of the study otherthan that it was an investigation of the easeof concept learning in children of varying levelsof language and cognitive skills. The experi-menter UJMD) observed each of the subjectsin the classroom for a minimum of one and ahalf hours prior to the onset of the project.Children were categorized on the basis ofwhether they used signs or speech during thisperiod. In addition, the reliability observerused throughout the experiment was an ad-

245


Table 1

Subject characteristics.

ChronologicalMental age age (in(in months) years-months)

Normal childrenAlex 30 2-6Bobby 37 2-11Claire 20 2-6Diane 19 2-1

Retarded/language childrenAllen 31 3-7Beth 36 4-4Carl 20 3-3David 19 2-8

Retarded/no-language childrenAndrew 30 4-1Barb 36 4-4Craig 18 4-4Debbie 14 2-7

vanced graduate student with many years ofexperience working with retarded and lan-guage-impaired children. He observed each ofthe subjects at least once for approximately anhour and was not informed of their previousclassification. After the session was completed,he was asked to categorize the child on thebasis of his or her behavior in the session. Inall cases, the three observers were in agree-ment.The children in the three groups were

matched for mental age on the basis of anindividual intelligence test (the Stanford-Bi-net Intelligence Scale, Form L-M, or the Bay-ley Scales of Infant Development). The re-tarded children were all assessed by personnelat their facility. The normal preschoolers wereassessed by the experimenter. There were fourlevels of mental age for each group, rangingfrom 14 to 36 months.The children's names were changed to pro-

tect confidentiality. Each child was given aname beginning with the same letter as thenames of his or her mental-age-matched con-trols. The mental-age scores and chronologi-cal ages of each child are presented in Ta-ble 1.

StimuliIn the training phase, the children were

taught four conditional discriminations: if A,then B; if D, then E; if A, then C; if D, thenF. Four tasks were learned by each child (A-

c

A

Ag

E

4 =TRAIN

<-> =TEST

Fig. 1. Examples of the stimulus figures used in thisexperiment.

B, D-E, A-C, and D-F). The tasks consistedof matching made-up animal-like figures us-ing a matching-to-sample format. On eachtrial, the A or D stimulus was presented as asample with either B and E or C and F ascomparisons. Each child was trained and testedusing a different stimulus set, made by ran-domly selecting from a pool of items. All ofthe stimulus figures were colored with water-color magic markers. Six colors were used:red, brown, green, purple, yellow, and orange.Each item was colored a different color. Colorassignment was random, except that all sixcolors had to be used in each set of stimuli. Ablack-and-white example of the stimuli isshown in Figure 1.

In a given trial, the three stimuli (one sam-ple and two comparisons) were presented on8½/2 x 11-in. sheets of white paper. When thelong side of the sheet was placed horizontally,the sample stimulus was at the top center ofthe page and the two comparisons were in thebottom half of the page, each 1.5 in. from theedge of the sheet. The left-right order of pre-sentation of the comparison stimuli was coun-terbalanced across trials to prevent the childfrom responding correctly on the basis of stim-ulus position. Each sheet contained the stimulifor one trial.The materials used in the test phase were

identical to those used in the training phase,except that the sample stimuli were stimulithat previously had been comparisons duringthe conditional discrimination training.Equivalence would be indicated by matching

246


between B and C, inasmuch as A had beenthe matching sample for both, and between Eand F, both of which had been matched to D.Ten trials of the test phase were devoted toeach of four types of problems: either B or Eas a sample with C and F as comparisons;either C or F as a sample with E and B ascomparisons.

SettingThe sessions for the retarded children were

held at a small table in an unused classroom.The child always sat at the table, which wasplaced against a wall. The experimental ma-terials were placed on the table in front of thechild or were held up off the table slightly topermit easier viewing. Sessions for the normalchildren were held in a small office. The childand the experimenter sat on a rug on the officefloor. The stimulus sheets were presented byplacing them on the floor directly in front ofthe child or by holding them slightly off thefloor.

ProcedureEach child was taught individually, and the

same training sequence was used for all. First,the child was taught to select B in the presenceof A (A-B). Then the child was taught to se-lect E in the presence of D (D-E). Then thesetwo tasks were mixed; the stimulus cards fromboth sets were mixed together and presentedin a random order. Once this task was mas-tered, training on A-C was begun. Then D-Fwas taught. Once D-F was mastered, A-C andD-F were mixed and presented to the child.When the child reached the mastery criterionon this mixed task, the stimulus items fromall four tasks were mixed and presented. Oncethe child reached the mastery criterion on thisfinal task, the test trials were presented. Themastery criterion used throughout training was9 of 10 consecutive unprompted responses cor-rect.

At the beginning of each session, the ex-perimenter greeted the child and spent severalmoments conversing. Even if the child wasnonverbal, the first portion of the session wasspent talking to the child in order to set arelaxed and pleasurable tone. The experi-menter started off the experimental procedureby saying, "I have some things I would likeyou to help me with. Let's see if you can helpme. I also have some things to play with and

we will play with those as well." For the re-tarded/no-language children this was short-ened to "Let's do some work," which was thestandard cue used for these children. The firsttask (A-B) was then presented. At the begin-ning of each trial, the experimenter pointedto the sample and said, "Touch the one thatgoes with this one."

For the normal children, correct responsesduring the training phase produced one ofseveral consequences including praise, blow-ing soap bubbles, and singing. Correct re-sponses by the retarded children produced briefaccess to tiny flashlights, soap bubbles, bal-loons, juice, and cheese crackers. When nec-essary, physical prompting (guiding the child'shand to the correct choice) and visual prompt-ing (placing the experimenter's finger on thecorrect choice) were used as teaching aids. Vi-sual prompting was used in a trial if the childhad failed to make a response during the pre-vious trial or if the previous two responses hadbeen incorrect. If the child's response follow-ing visual prompting was correct, the visualprompt was faded by placing a finger 2 in.away from the correct stimulus on the nexttrial, 6 in. away on the next trial, and thenremoving the prompt entirely. Physicalprompting was used if the visual prompt failedto produce correct responding. After guidingthe child's hand to the correct choice, thephysical prompt was faded on subsequenttrials. First, very light pressure was used toguide the child's hand, then the experiment-er's hand shadowed the child's without anyguidance, then the child's hand was touchedbriefly after the choice, and finally the promptwas removed entirely. If an incorrect responseoccurred, the previous level of assistance wasreinstituted.

Initially, all correct responses led to the de-livery of one of the consequences. At the endof the training phase, when the conditionaldiscriminations were mixed and presented, theschedule was gradually thinned until a pro-grammed consequence was delivered only af-ter every three or four correct responses. Thiswas done to equate the rate of reinforcementto that used in the testing phase.

In the test phase, 40 trials were presented.Rewards contingent on responses consistentwith the formation of an equivalence classwere not delivered during testing. The com-position of these trials has already been de-

247


Table 2Number of sessions to final mastery criterion.

Alex 2 Bobby 2Allen 7 Beth 6Andrew 16 Barb 8Claire 16 Diane 21Carl 7 David 11Craig 14 Debbie 16

scribed. The four trial types were randomlyintermixed. After every third or fourth re-sponse (correct or incorrect), the child waspraised or one of the other programmed con-sequences was delivered for cooperation, goodsitting, and the like. If the child asked forexplicit feedback about a response, the exper-imenter said, "In this part of the game, I mustbe very quiet. I think you are doing a goodjob of working on this."The data were collected over several ses-

sions with each child. Most sessions lasted ap-proximately 20 min, and no session ran longerthan 30 min. The number of sessions requiredto reach the final training mastery criterion ispresented in Table 2. The equivalence testwas always conducted immediately after thechild reached the final mastery criterion. Forsome children, this occurred near the end of asession; for others this occurred near the be-ginning.

Recording and ReliabilityBehavior in each trial was scored as "cor-

rect," "incorrect," or "no response." The ex-perimenter was the primary data collector. Acorrect response was defined as touching thecorrect comparison stimulus while refrainingfrom touching the incorrect comparison or thesample stimulus. An incorrect response wasdefined as touching the incorrect comparison,touching the sample, touching both the correctcomparison and the sample or incorrect com-parison, or touching another part of the stim-ulus sheet. A no response was defined as anyother behavior. In the testing phase, the "cor-rect" response was the response that would beexpected if an equivalence class had formed.

Reliability data were collected in 20% ofthe sessions, distributed across children. Thesedata were collected by a trained graduate stu-dent who was familiar with the general na-ture of the project but was unfamiliar withthe specific hypothesis. The rater sat in a po-

Table 3Interobserver agreement during multiple sessions whenreliability measures were obtained.

Number of trials Agreement

67 8860 100150 96260 100200 100120 100

sition from which he could not observe theexperimenter's data sheet. During sessions inwhich the observer was present, the experi-menter paused briefly after each trial beforedelivering the consequence, permitting the ob-server to record the data without knowledgeof the experimenter's scoring.

Reliability was calculated on a trial-by-trialbasis using the formula [Agreements/(Agree-ments + Disagreements)] x 100. An agree-ment was scored if the two observers both re-corded a response as correct or as incorrect.For the purposes of reliability computations,a prompted trial was considered correct. In-terobserver agreement per session ranged from88% to 100%. These data are summarized inTable 3.

RESULTSConditional Discrimination TrainingThe individual data grouped by measured

mental age are presented in Figures 2, 3, 4,and 5. In each figure, the data for the matchednormal child, retarded/language child, andretarded/no-language child are presented. Thedata are graphed as the percentages of un-prompted correct responses in blocks of 10consecutive trials.An inspection of the individual data shows

that performance varied among the three sub-ject groups. The retarded/language and nor-mal groups consistently required fewer trialsto complete the conditional discriminationtraining than did children in the retarded/no-language condition. In the normal group, Alexrequired 95 trials to complete the training,and Bobby required 107 trials; Claire re-quired 185 trials, whereas Diane required 273trials. In the retarded/language group, Allenrequired 277 trials, Beth required 223 trials,Carl required 227 trials, and David required


ALEX- Normal

1001 0 0/0 0 00 0 -O

0 A-BJE MIX C F MIX MIX TEST

ALLEN- Retarded Lang

000*~~ 1

A-C MIX *MIX

0

0 *I/ 1-

TEST

BLOCKS OF TEN TRIALSFig. 2. Individual training and testing data for Alex, Allen, and Andrew (MA = approximately 30 months). The

data are presented as the percentage of correct unprompted trials (vertical axis) across blocks of 10 trials (horizontalaxis).

264 trials. In the retarded/no-language group,Andrew required 507 trials, Barb required 280trials, Craig required 370 trials, and Debbierequired 750 trials.An analysis of variance indicated a signifi-

cant difference among the three groups in thenumber of trials needed to complete the con-ditional discrimination training, F(2, 9) =6.34, p < .019. A Newman-Keuls post-hocanalysis (Ferguson, 1976) revealed no signif-icant difference between the normal and theretarded/language group, but did betweenthese groups and the retarded/no-languagegroup (p < .05).There was also a difference among the three

groups in the number of prompts used in theconditional-discrimination training. The meannumber of prompts (visual and manual) usedper child was 29 for the normal group, 40 for

the retarded/language group, and 184 for theretarded/no-language group.

Equivalence TestThe test data are presented in different form

in Figure 6. Each graph represents one sub-ject. The columns in each individual graphrepresent the number of "no responses" madeby the child during each block of 10 trials. As"no responses" do not allow us to determineif an equivalence class has formed, the per-centages of correct responding were calculatedas the number of correct responses divided bythe total number of responses in that block.Each row of graphs represents the data fromone group with respect to language. Each col-umn of graphs represents the data for thosechildren matched for mental-age scores (acrossgroups).

100-

A-D-B E MIX

0c-U

w

Uz

cr:wCL

249


0I B0 BY r

/ - ~BOBBY- Normal

___/

MIX

S

55-4/

MIX

I.p/ BETH- Retarded Lang

S

TEST

100-BARB- Retarded No Lang

A-B

l

D-E

0

I.1

A-C D-F

'p

MIX

0

, /

MIX (all)

A

TEST

BLOCKS OF TEN TRIALSFig. 3. Individual training and testing data for Bobby, Beth, and Barb (MA = approximately 36 months). The


The data confirmed the prediction that thelanguage-able children would perform betterthan the language-deficient children on thestimulus-equivalence test. Calculated as justdescribed, the average correct responding inthe test phase in the normal group was 84.5%.In the retarded/language group, the averagepercentage of correct responding was 78.25%.In the retarded/no-language group, the av-

erage correct responding was 44.5%-veryclose to chance level (50%). No increase across

trials in the number of no responses was seen

in any group. The effects were quite consis-tent across children with widely varying mea-

sured mental age. Every one of the subjects inthe normal and retarded/language groupsshowed high percentages of correct respond-ing, whereas the performances of all of thechildren in the retarded/no-language groupremained near chance level throughout. Theexception to this was Craig (column C, third

graph). His performance deteriorated duringthe test until correct responding was at 0%.Notations made on the data sheets during thetest phase indicated that he consistentlytouched the center (white space) of the stim-ulus sheets rather than consistently choosingthe incorrect comparison stimulus.

All of the normal and retarded/languagechildren improved from the first to the lasthalf of the testing period. For the normal chil-dren, the mean percentage of correct respond-ing in the first half was 77.75%, and the meanfor the second half was 95.5%. For the re-tarded/language children, the mean percent-age of correct responding in the first half was69.75%, and during the second half, 88%. Forthe retarded/no-language group, mean cor-rect responding during the first half was

46.25%, and during the second half, 39.25%.Improvement in performance during testingwithout reinforcement procedures has previ-

250

I10

0

0

1001

100-i

0

D-D-A-B E MIX MIX TESTMIX -C

MIX

i

A-B

05

S0

D-E

0

A-C

/j

D-F

.


D-E

/0

0A-B

0

MIX

0

0-@'

A-C

0

/

0~

*.4

D-E

MIX

/

o

MIX

I.

eq

MIX

AO

A-C

CLAIRE- Normal

CARL- Retarded Lang

0-0-0

TEST

/

D-F

BLOCKS OF TEN TRIALSFig. 4. Individual training and testing data for Claire, Carl, and Craig (MA = approximately 20 months). The


ously been found in the equivalence literature(e.g., Sidman, Kirk, & Willson-Morris, 1985).A one-way ANOVA on the percentage of

correct responding confirmed that the lan-guage-able children performed significantlybetter than the language-deficient children onthe stimulus equivalence test, F(2, 9) = 18.51,p <.0006. A Newman-Keuls analysis re-vealed no significant difference between thenormal and the retarded/language group, butdid between the retarded/no-language and thenormal (p < .01) and the retarded/language(p < .01) groups.

DISCUSSIONDuring the test, each language-able child

showed the formation of equivalence classes,whereas each language-disabled child per-formed at chance level. Although correla-tional, the data provide support for the viewthat symbol use and the ability to form equiv-

alence classes are closely related. These resultswere found consistently with children acrossa range of chronological ages and mental-agescores. They included the youngest child (25months) yet reported to show formation of anequivalence class, indicating that extensivelanguage training or mastery is apparently notrequired for the formation of equivalenceclasses. In addition, for the first time, a clearlyspecified group of humans has been identifiedwho apparently fail to form equivalenceclasses.The results showed that this deficit cannot

be explained on the basis of an inability tolearn conditional discriminations per se. Theretarded/no-language children required moretrials and more prompts than the children inthe other two groups to meet the mastery cri-terion in the conditional-discrimination train-ing portion of the project. These data are con-sistent with reports on the acquisition ofdiscriminations and conditional discrimina-

100-wcc

0

cc

0

zw

wa-A-B

100-CRAIG -Retarded No Lang

0

A/'0 0mix

TEST

251


DIANE-Normal

ILang

BLOCKS OF TRIALSFig. 5. Individual training and testing data for Diane, David, and Debbie (MA = approximately 19 months). The


tions by retarded children with severely lim-ited language abilities (e.g., Churchill, 1978;Lovaas, 1977; Routh, 1973). All the retarded/no-language children did acquire all the con-ditional discriminations, however, and wereeventually able to respond consistently andcorrectly without prompting. None subse-quently showed stimulus equivalence as a re-sult of this successful training.

Supplementary data collected post hoc withretarded/no-language subjects and not re-ported here (see Devany, 1985) support theview that the failure of the retarded/no-lan-guage children on the equivalence test was notdue to the use of unfamiliar, abstract, or non-salient visual stimuli, nor to a failure to showgeneralized identity matching, but seemed tobe related to the lack of symmetrical respond-ing. Whenever symmetry has been shown inthe equivalence literature, transitivity has alsobeen found.

Different results might have been obtainedhad a more stringent mastery criterion beenused than the one used here (9 of 10 responses

correct). Once the criterion was met, subjectsproceeded immediately to the next phase oftraining or to testing. This may have pre-cluded overtraining, which can alter the per-formance of severely handicapped individuals(Shover & Newsom, 1976). Had the trainingbeen greatly extended, the language-disabledchildren might have shown the developmentof equivalence classes. A major purpose, how-ever, of overtraining would be to ensure thatthe baseline conditional discriminations weremaintained. Because the subjects in the pres-ent study were tested immediately followingmastery of the mixture of all four discrimi-nations, maintained in the presence of athinned schedule of reinforcement, it seemsunlikely that the baseline discriminationswould have deteriorated during the brief test-ing period.

It also seems unlikely that the responses ofthe children in the retarded/no-languagegroup were extinguished during testing, as thelevel of noncontingent reinforcement in testingwas matched to the level of contingent rein-

252


Retarded Lang0

0-00 _

n nnn

.II*/n11

, 0

goo0

.00

1n Ii

Retarded No Lang

5

. . - U

Lai aa5

/0 ~.*...- 7Hnn n

0

0

nnn

0

/ilFnSn 5

BLOCKS OF TRIALSFig. 6. Individual test data. Each graph presents the data for one child. Each column of graphs presents the data

for those children in a particular language group. Each row of graphs presents the data for those children matchedfor mental age. The data (dots) are presented as the percentages correct (of all responses attempted) across blocks of10 trials. The columns within each graph present the number of no responses that occurred within that block of 10trials.

forcement used by the end of the training. Also, children differed from the other children inthe testing phase might have been too short ways other than a failure to speak or sign.for these children to demonstrate equivalence They required substantially more training toclasses, but this is not supported by trends in meet the mastery criterion and needed moretheir testing data. prompting, for example. Matching by mental-

It is true that the retarded/no-language age scores can only crudely equate children on

9QI

CZ

Normal

100

02

7-*I?

50

100

*A/.00*0

nn

01--10-n .000

Ianr1IL

-0

nfl

Lu

zLu0L

lh

*

m5

lA*co

50

100

50

zCKi

, wmm

m0

z0m

C')*5 Z

CO)mC')

100-

50

253

/lw

0

n n..

i

-

v0

0

n


their level of intelligent behavior. These in-telligence tests include some items that requireverbal abilities and others that do not. Thus,a child without language skills could bematched on MA to a child with language skillsonly by having better developed nonverbalskills. The precise pattern of such abilities,and their causes, may be important in the for-mation of equivalence classes. Although lan-guage ability per se cannot be pinpointed asthe source of the differences seen, these resultsmake that possibility more plausible. It mightbe possible to disentangle this issue from thatof retardation per se by examining equiva-lence-test performance of aphasic children withnormal performance (nonverbal) IQ scores.Yet the important point here is that despiteconsiderable heterogeneity within groups on avariety of measures, including trials to crite-rion, prompts, mental-age scores, and chrono-logical age, there was no evidence of a rela-tionship between these differences andequivalence-test performance within groups.Thus, there seems to be little basis for ap-pealing to these variables as the source of thedifferences seen between groups. For exam-ple, the youngest normal child (Diane) took273 trials to acquire the baseline conditionaldiscriminations, and one of the higher MAretarded/no-language children (Barb) re-quired 280 trials. However, Diane showed theacquisition of equivalence classes, but Barbdid not.

It is not possible to say from these datawhether the ability to form equivalence classesis a precursor of symbol use, a product of it,or if the two are both a reflection of the sameprocess. It could be that the ability to formequivalence classes is a unique and distinctskill that itself is required for stimuli to beused symbolically. Conversely, language maybe a distinct skill that in turn permits the for-mation of equivalence classes. Finally, it ispossible that both the formation of equiva-lence classes and the acquisition of languageare the result of other common processes.

Further analyses of the performances of veryyoung developing children might help clarifythis issue. If, for example, performance on anequivalence test is excellent before the childhas acquired any labels, the argument that theability to form equivalence classes is distinct(e.g., Sidman, 1986) and may itself lead tolanguage acquisition would be strengthened.

Similarly, if successful language training alsoestablishes equivalence-class formation in re-tarded children, the effect of language onequivalence classes would be implicated. If thetwo areas are essentially synonymous or if theyboth reflect common behavioral properties(such as the ability to respond in terms ofarbitrary relations per se [e.g., Hayes, 1986;Hayes & Brownstein, 1985]), training inequivalence-class formation or its presumedunderlying behavioral process should assist inlanguage acquisition, and vice versa.

Improvement during testing. All of the lan-guage-able children showed improvement intest performance across blocks of test trials.This improvement in performance duringtesting has been seen in several studies (Lazar,Davis-Lang, & Sanchez, 1984; Sidman et al.,1985), although this study is the first in whichthe effect was seen in blocks of testing trialswithout conditional-discrimination traininginterspersed between test trials. The results ofthis project demonstrate that the interspersalof test and training trials is not necessary forthe occurrence of improvement during testingand that improvement across the course oftesting may be seen when testing trials arepresented in a massed (as opposed to inter-spersed) format.The reasons for this improvement are not

clear. The improvement suggests that rein-forcement of correct responding was occur-ring. In this project, however, responses wereneither explicitly rewarded nor punished inthe test phase. Any reinforcement that oc-curred in the test phase was unprogrammed.One possible source of reinforcement may havebeen subtle cues emitted by the experimenter(the Clever Hans effect; Sebeok, 1980). Al-though every effort was made to minimize anysuch cues, the possibility of subtle differentialreactions cannot be disregarded. This im-provement during testing, however, has beenobtained repeatedly in studies in which au-tomated equipment was used, which pre-vented the possibility of differential feedback(e.g., Sidman et al., 1985).

It has been suggested (Sidman et al., 1985)that this improvement occurs because theequivalence test itself provides a context inwhich the equivalence class is formed. In thisview, the conditional-discrimination trainingprovides the necessary history and the intro-duction of testing trials provides the necessary

254


context in which equivalence classes areformed. Alternatively, it may be that equiva-lence classes emerge during testing in part be-cause humans have histories in which re-sponding consistently had been more likely tobe reinforced. In this view, subjects may dis-criminate the source of control over responsesin each trial. At first, for example, a responsemay be at strength because one of the stimuliis pretty. Another may be at strength becauseone of the comparison stimuli looks like thesample stimulus. These bases, however, do notprovide consistently strong responding in alltrials and thus are discarded because rein-forcement has rarely followed inconsistent re-sponding in the past. Thus, perhaps a kind ofresponse-contingent feedback is provided dur-ing testing-namely, the presence of respond-ing based on a common source of control. Onlyresponding controlled by an equivalence classwill be at strength in every trial to which thesubject is exposed, and thus over trials re-sponses controlled by the equivalence classcome to dominate other possible responses.This could be tested by including some irrel-evant trials (with no correct answer based onequivalence) interspersed with the other test-ing trials. If this analysis is correct, this pro-cedure should interfere with the formation ofequivalence classes.

Receptive language and instructional control.The receptive language skills of the childrenin this project were not formally assessed. Allof the children responded to simple instruc-tions, such as "Sit down" and to consequencessuch as "No!," but the extent to which theycould comprehend labels and other conversa-tion is not known. Because this study usedonly novel visual stimuli, the extent to whichreceptive language skills might have contrib-uted to success or failure in establishingequivalence classes is not clear. However, thereare some data (Remington, 1985) indicatingthat receptive language may be an importantvariable in the formation of equivalenceclasses.

Because receptive language appears to be amatter of control by symbolic stimuli, stimu-lus equivalence may be relevant to rule-gov-erned behavior. A growing body of literature(Baron & Galizio, 1983; Hayes, in press) sug-gests that human actions under the control ofrules or instruction differ fundamentally fromthose under control of direct contingencies of

reinforcement. If equivalence classes have todo with language, we would also expect thecontrol such stimuli exert over behavior toparallel the control that instructions seem toexert over behavior in humans. The availableevidence, while still limited, indicates that thisis what occurs. For example, if the spoken andwritten words "men" and "boys" and picturesof males are part of an equivalence class("males"), and a boy learns to enter the "men'sroom" at a restaurant, he may also come toenter the "boy's room" at another, or the roomwith a drawing of a stick person with pantsat a third, without explicit training to do so.As a parallel, after an equivalence class (ABC)is formed, if one member (A) becomes dis-criminative for a response, then B and C willalso become discriminative for the same re-sponse (Hayes, Brownstein, Devany, Kohlen-berg, & Shelby, 1985; see also Lazar, 1977).To take another example, if someone is toldthat the word for "good" in French is "bon,"and the word for "bon" in Spanish is "bueno,"and if "good" functions as a conditioned rein-forcer for behavior, it seems likely that"bueno" will now also do so, without "bueno"ever having been paired with positive reinfor-cers. Similar results have been found withequivalence classes (Hayes et al., 1985).

Thus, it may be possible that instructionalcontrol is based fundamentally on stimulusequivalence as a behavioral process (Hayes,1986; Hayes & Brownstein, 1985). For ex-ample, consider a dog's approach to its ownerwhen commanded "come here." The action ofthe dog seems similar to the behavior of ahuman being when given the same command.There appears to be nothing special about thecontrol exerted by verbal stimuli over a hu-man as compared with the control exerted overan infrahuman by discriminative stimuli moregenerally. It is possible, however, that thesource of control over the action of the dogand human is different. The words "comehere" may be effective for the dog because inthe past the probability of reinforcement forapproach was higher in their presence thanin their absence. The human, however, maybe responding not because of a direct historyof this sort, but in part because these stimuliparticipate in equivalence classes establishedby the verbal community. Their discrimina-tive effect may be only indirectly tied to a di-rect history of reinforcement involving other

255

256 JEANNE M. DEVANY et al.

members of the class, or to additional classesrelated to the class. If so, rules and instruc-tions may exert their control through very dif-ferent processes than do typical discriminativestimuli.The data from this project support the view

that there is a relation between the ability toform equivalence classes and language. Spe-cifically, the language-disabled children wereshown to be unable to form equivalence classesunder conditions in which very young normaland language-able retarded children were eas-ily able to do so even though they masteredthe requisite conditional discriminations. Thisconnection between language and stimulusequivalence may lead to the development oftraining techniques for the remediation of lan-guage and generalization deficits in develop-mentally disabled populations.

In the thirty years since the publication ofVerbal Behavior (Skinner, 1957), empiricalprogress in the behavior-analytic understand-ing of language has been disappointing. Thismay be, in part, because research has focusedon the behavior of the speaker, creating no-table difficulties for a behavior-analytic ap-proach in the areas of response definition andmeasurement (Hayes & Brownstein, 1984). Ifthe present analysis is correct, the study ofstimulus equivalence provides another, possi-bly more fruitful, avenue for the study of lan-guage phenomena.

REFERENCESBaron, A., & Galizio, M. (1983). Instructional control

of human operant behavior. Psychological Record, 33,495-520.

Churchill, D. W. (1978). Language of autistic children.Washington, DC: V. H. Winston.

Clark, H. H., & Clark, E. V. (1977). Psychology andlanguage: An introduction to psycholinguistics. New York:Harcourt, Brace, Jovanovich.

D'Amato, M. R., Salmon, D. P., Loukas, E., & Tomie,A. (1985). Symmetry and transitivity of conditionalrelations in monkeys (Cebus apella) and pigeons (Co-lumba livia). Journal of the Experimental Analysis of Be-havior, 44, 35-47.

Devany, J. M. (1985). Stimulus equivalence and languagedevelopment in children. Unpublished doctoral disser-tation, University of North Carolina-Greensboro.

Dixon, M. (1976). Teaching conceptual classes withreceptive label training. Acta Symbolica, 7, 17-35.

Dixon, M., & Spradlin, J. (1976). Establishing stim-ulus equivalences among retarded adolescents. Journalof Experimental Child Psychology, 21, 144-164.

Edwards, C. A., Jagielo, J. A., & Zentall, T. R. (1983)."Same/different" symbol use by pigeons. AnimalLearning & Behavior, 11, 349-355.

Ferguson, G. A. (1976). Statistical analysis in psychologyand education (4th ed.). New York: McGraw-Hill.

Fouts, R. S., Chown, B., & Goodin, L. (1976). Transferof signed responses in American Sign Language fromvocal English stimuli to physical object stimuli by achimpanzee (Pan). Learning and Motivation, 7, 458-475.

Gast, D. L., VanBiervliet, A., & Spradlin, J. E. (1979).Teaching number-word equivalences: A study oftransfer. American Journal ofMental Deficiency, 83, 524-527.

Hayes, S. C. (1986). The case of the silent dog-Verbalreports and the analysis of rules. A review of Ericcson& Simon's, Protocol Analysis: Verbal Reports as Data.Journal of the Experimental Analysis of Behavior, 45,351-363.

Hayes, S. C. (Ed.). (in press). Rule-governed behavior:Cognition, contingencies, and instructional control. NewYork: Plenum Press.

Hayes, S. C., & Brownstein, A. J. (1984). Verbal be-havior: Is the human operant laboratory an ideal placeto begin? Experimental Analysis of Human BehaviorBulletin, 2, 11-13.

Hayes, S. C., & Brownstein, A. J. (1985, May). Verbalbehavior, equivalence classes and rules: New definitions,data, and directions. Paper presented at the annualmeeting of the Association for Behavior Analysis, Co-lumbus, OH.

Hayes, S. C., Brownstein, A., Devany, J., Kohlenberg,B., & Shelby, J. (1985, May). Stimulus equivalenceand the acquisition of meaning. Paper presented at theannual meeting of the Association for Behavior Anal-ysis, Columbus, OH.

Herman, L. M., & Thompson, R. K. R. (1982). Sym-bolic, identity, and probe delayed matching of soundsby the bottlenosed dolphin. Animal Learning & Behav-ior, 10, 22-34.

Kendall, S. B. (1983). Tests for mediated transfer inpigeons. Psychological Record, 33, 245-256.

Lashley, K. S. (1938). Conditional reactions in the rat.Journal of Psychology, 6, 311-324.

Lazar, R. (1977). Extending sequence-class member-ship with matching to sample. Journal of the Experi-mental Analysis of Behavior, 27, 381-392.

Lazar, R. M., Davis-Lang, D., & Sanchez, L. (1984).The formation of visual stimulus equivalences in chil-dren. Journal of the Experimental Analysis of Behavior,41, 251-266.

Lovaas, 0. I. (1977). The autistic child. New York: Ir-vington.

Mackay, H. A., & Sidman, M. (1984). Teaching newbehavior via equivalence relations. In P. H. Brooks,R. Sperber, & C. McCauley (Eds.), Learning and cog-nition in the mentally retarded (pp. 493-513). Hillsdale,NJ: Erlbaum.

Nelson, K. (1974). Concept, word, and sentence: Inter-relations in acquisition and development. PsychologicalReview, 81, 267-285.

Nissen, H. W. (1951). Analysis of a complex condi-tional reaction in chimpanzee. Journal of Comparativeand Physiological Psychology, 44, 9-16.

Premack, D. (1976). Intelligence in ape and man. Hills-dale, NJ: Erlbaum.

STIMULUS EQUIVALENCE AND LANGUAGE 257

Remington, R. (1985, April). Is signing a substitute forspeech with retarded children? Paper presented at theUniversity of North Carolina-Greensboro.

Routh, D. K. (Ed.). (1973). Theexperimentalpsychologyof mental retardation. Chicago: Aldine.

Savage-Rumbaugh, E. S. (1984). Verbal behavior at aprocedural level in the chimpanzee. Journal of the Ex-perimental Analysis of Behavior, 41, 223-250.

Sebeok, T. (1980). Looking in the destination for whatshould have been sought in the source. In T. A. Sebeok& J. Umiker-Sebeok (Eds.), Speaking ofapes (pp. 407-428). New York: Plenum Press.

Shover, L. R., & Newsom, C. D. (1976). Overselectiv-ity, developmental level, and overtraining in autisticand normal children. Journal of Abnormal Child Psy-chology, 4, 289-298.

Sidman, M. (1971). Reading and auditory-visualequivalences. Journal of Speech and Hearing Research,14, 5-13.

Sidman, M. (1986). Functional analysis of emergentverbal classes. In T. Thompson & M. D. Zeiler (Eds.),Analysis and integration of behavioral units (pp. 213-245). Hillsdale, NJ: Erlbaum.

Sidman, M., Cresson, O., Jr., & Willson-Morris, M.(1974). Acquisition of matching to sample via me-diated transfer. Journal of the Experimental Analysis ofBehavior, 22, 261-273.

Sidman, M., Kirk, B., & Willson-Morris, M. (1985).Six-member stimulus classes generated by conditional-discrimination procedures. Journal of the ExperimentalAnalysis of Behavior, 43, 21-42.

Sidman, M., Rauzin, R., Lazar, R., Cunningham, S.,Tailby, W., & Carrigan, P. (1982). A search forsymmetry in the conditional discriminations of rhesusmonkeys, baboons, and children. Journal of the Exper-imental Analysis of Behavior, 37, 23-44.

Sidman, M., & Tailby, W. (1982). Conditional dis-crimination vs. matching to sample: An expansion ofthe testing paradigm. Journal of the Experimental Anal-ysis of Behavior, 37, 5-22.

Skinner, B. F. (1957). Verbal behavior. New York: Ap-pleton-Century-Crofts.

Spradlin, J. E., Cotter, V. W., & Baxley, N. (1973).Establishing a conditional discrimination without di-rect training: A study of transfer with retarded ado-lescents. American Journal ofMental Deficiency, 77, 556-566.

Spradlin, J. E., & Dixon, M. H. (1976). Establishingconditional discriminations without direct training:Stimulus classes and labels. American Journal ofMentalDefciency, 80, 555-561.

VanBiervliet, A. (1977). Establishing words and objectsas functionally equivalent through manual sign train-ing. American Journal of Mental Deficiency, 82, 178-186.

Wetherby, B., Karlan, G. R., & Spradlin, J. E. (1983).The development of derived stimulus relations throughtraining in arbitrary-matching sequences. Journal ofthe Experimental Analysis of Behavior, 40, 69-78.

Received August 15, 1985Final acceptance June 17, 1986

1977), (Nel- - Illinois State University Websites et... · journal oftheexperimental analysis of...

Documents

Transcript of 1977), (Nel- - Illinois State University Websites et... · journal oftheexperimental analysis of...