Do equivalence classes mediate extensions of stimulus function?

85 Pages·2000·2.6 MB·English

by  Vaidya, Manish

DOEQUIVALENCECLASSESMEDIATEEXTENSIONS
OFSTIMULUSFUNCTION?
By
MANISHVAIDYA
ADISSERTATIONPRESENTEDTOTHEGRADUATESCHOOL
OFTHEUNIVERSITYOFFLORIDAINPARTIALFULFILLMENT
OFTHEREQUIREMENTSFORTHEDEGREEOF
DOCTOROFPHILOSOPHY
UNIVERSITYOFFLORIDA
2000
TABLEOFCONTENTS
ABSTRACT '»
GENERALINTRODUCTION 1
EXPERIMENT1 11
Method 12
Results 17
Discussion 37
EXPERIMENT2 42
Method 45
Results 48
Discussion 66
GENERALDISCUSSION 70
APPENDIX:INSTRUCTIONS 74
REFERENCES 75
BIOGRAPHICALSKETCH 79
ii
AbstractofDissertationPresentedtotheGraduateSchool
oftheUniversityofFloridainPartialFulfillmentofthe
RequirementsfortheDegreeof
DoctorofPhilosophy
DOEQUIVALENCECLASSESMEDIATEEXTENSIONS
OFSTIMULUSFUNCTIONS?
By
ManishVaidya
May,2000
Chairperson:TimothyD.Hackenberg,Ph.D.
MajorDepartment:Psychology
Stimulusequivalenceisdemonstratedwhenthefunctionsofstimuli
establishedinreinforcedconditionaldiscriminationtrialsareshowntobe
interchangeableinunreinforcedconditionaldiscriminationtrialsinvolvingthesame
stimuliinnovelconfigurations. Althoughmuchhasbeenlearnedaboutequivalence
relations,thepreparationstypicallyusedhavenotallowedapreciseunderstanding
oftherelationshipbetweentrainedandderivedconditionalrelationsortheroleof
equivalenceclassesinmorecomplexbehavioralrelations. Thepurposeof
Experiment1 wastoattemptamorepreciseunderstandingoftherelationship
betweentheacquisitionoftrainedconditionaldiscriminationsandtheemergenceof
untrainedconditionaldiscriminations. Sixundergraduatestudentswereexposedto
18conditionaldiscriminationtrialtypesdesignedtotrainandtestfor33-member
equivalenceclassesfromthebeginningoftheexperiment. Oncechoiceswere
stable,thecontingenciesfor2of6trainedrelationswerereversed. Theresults
showedthattherewasalagbetweentheacquisitionofthetrainedconditional
relationsandtheemergenceofderivedconditionalrelationsthatdefineequivalence
classes. Inaddition,thereversalofcontingenciesforasubsetofthetrainedoriginal
relationsproducedchangesonsomeofthederivedconditionaldiscriminationsbut
notothers. Thesedatasuggestedthat(a)thebehavioralprerequisitesfor
conditionalrelationsandequivalencerelationsarenotidenticaland(b)thedifferent
stimuluscontrolrelationsthatdefineanequivalencerelationcanvaryindependent
ofoneanother. ThepurposeofExperiment2wastoascertaintheroleof
equivalenceclassesintheextensionofstimulusfunctionsacrossclassmembers.
Threeundergraduatestudentswereexposedtotheconditionaldiscriminationtask
describedabovewithasuccessivesimplediscriminationtaskinterlacedthroughout
thesessionfromthebeginningoftheexperiment. Theresultsshowedthat
extensionofstimulusfunctionwassometimes(a)observedpriortothedevelopment
ofequivalencerelationsand(b)notobserveddespitetheformationofequivalence
relations. Thesedatasuggestthatequivalenceclassesareneithernecessarynor
sufficientfortheextensionofstimulusfunctions. Takentogether,theseresultscall
intoquestiontheassumedintegratednatureofequivalencerelationsandtheirrolein
theextensionofstimulusfunctions.
iv
GENERALINTRODUCTION
Someoftheoldestquestionsinpsychologypertaintoreferenceand
meaning. How,forexample,dosymbolscometorepresent,orreferto,other
figures,objects,orevents?Earlybehavioristaccountssuggestedsimplesubstitution
astheanswer. Asymbolwassaidtomeanthesamethingasitsreferenttothe
extentthatsymbolandreferentproducedthesamekindofbehavior. AsWatson
(1924)putit:
[w]ordsnotonlycananddocalloutotherwords,phrasesandsentences,but
whenthehumanbeingisproperlyorganizedtheycancalloutallofhis
manualactivity. Thewordsfunctioninthemannerofcallingoutresponses
exactlyasdidtheobjectsforwhichthewordsserveassubstitutes(p.233).
Althoughcurrentapproachesnolongerassume thatreference-likerelationsinvolve
thecompletesubstitutabilityofsymbolsforobjectsorevents, thefundamental
problemofreferenceandmeaninghasscarcelybeenresolved. Thekeyissue,as
Watsonrecognized,lieswiththeextensionofstimulusfunction,orthe
circumstancesinwhichaneutralstimulusmaycometofunctioninamannersimilar
toanalreadyestablishedstimuluswithoutdirecttraining.
Someimportantconceptualandempiricaladvancesinthestudyofuntrained
extensionsofstimulusfunctionhavecomefromanareaknownasstimulus
equivalence(Sidman, 1971, 1994). Briefly,researchinstimulusequivalenceis
concernedwiththestudyoftheorigin,maintenance,andmodificationofbehavior
undercontrolofrelationsbetweenstimuli. Theexperimentalpreparationusedto
investigateequivalencerelationsgenerallyinvolvesaconditionaldiscrimination
procedureinwhichasubjectchoosesoneofseveralavailablestimuli(called
comparisonstimuli)conditionallyuponthepresenceofanotherstimulus(calledthe
samplestimulus). Choosingtheexperimenter-designated"correct"comparison
producesareinforcingconsequencewhereaschoosinganyothercomparisonends
thetrialwithoutreinforcement. Asubjectisexplicitlytaughtseveralinterrelated
conditionaldiscriminations(e.g.,givenA1 pickB1,notB2orB3;givenB1 pickC1,
notC2orC3)andthentestedfortheemergenceofotherconditionaldiscriminations
thatwerenotdirectlytrained(e.g.,givenB1 pickA1,notA2orA3;givenC1 pick
B1,notB2orB3;givenA1 pickC1,notC2orC3;andgivenC1 pickA1,notA2or
A3). Accurateperformanceonthesenovelconditionaldiscriminations,inthe
absenceofreinforcement,issaidtoindicatetheexistenceofanequivalencerelation
amongthestimuli(Sidman&Tailby, 1982).
Thesestimulus-equivalencerelationsaredefinedintermsof3propertiesthat
defineequivalentsetsinmathematics-reflexivity,symmetryandtransitivity(Sidman
&Tailby, 1982). Thepropertyofreflexivityisseenwhenasubjectselects
comparisonstimulithatarephysicallyidenticaltothesamplestimuli. Forexample,
giventrainingtopickA1 givenA1,asubjectpicksB1 givenB1 without
reinforcementfordoingso. Thepropertyofsymmetryisseenwhenthesampleand
comparisonfunctionsofstimulibecomeinterchangeable. Forexample,givena
historyofreinforcementforselectingB1 givenA1 assample,asubjectselectsA1
givenB1 asasamplewithoutreinforcementfordoingso. Thepropertyof
transitivityisseenwhenthesamplefromoneconditionaldiscriminationexerts
conditionalcontrolovertheselectionofacomparisonfromadifferent,butrelated,
conditionaldiscrimination. Forexample,givenahistoryofselectingB1 givenA1
.
3
andselectingC1 givenB1,asubjectselectsC1 givenA1 asthesample. These
relationshipsareillustratedschematicallyinFigure1
Thisthree-partdefinitionhasbeenextremelyimportantinestablishingaclear
matrixofbehavioraltasksthatcanbeusedtoindicatethepresenceorabsenceof
equivalencerelationsamongthestimuli. Asanexample,consideranexperiment
reportedbySidman(1971). Usingaslightlydifferenttrainingstructure,a
developmentallydelayedsubjectwastrainedtoselectapictureofacat(B1)given
thespokenword"cat"(A1)andtoselectthewrittenwordCAT(CDgiventhe
spokenword"cat"(A1). Asaresultofthistrainingthesubjectcametorespond
accuratelyonotherconditionaldiscriminationsthathadnotbeendirectlytrained.
Forexample,itwasfoundthatthesubjectcouldnowselectthepictureofacat
(B1)giventhewrittenwordCAT(CDasastimulusandselectthewrittenword
CAT(CDgiventhepictureofacat(B1). Sidman(1971)concludedthat,byvirtue
oftheconditionaldiscriminationtraining,thestimulihadbecomesubstitutableor
"equivalent"withinthecontextoftheconditionaldiscriminationprocedure.
Animportantfeatureofthesestimulus-equivalenceclassesisthe
demonstrationthatstimulithatbecomeequivalentinthecontextofaconditional
discriminationtaskcanalsobecomeequivalentinothercontexts. Basedonthe
observationthatstimulusfunctionsextendacrossmembersofequivalenceclasses,
ithasbeensuggestedthatthecontextofstimulusequivalenceexperimentsmay
serveasausefullaboratoryanalogueforthestudyofextensionsofstimulus
functionsinnaturallanguages,providingapotentialbasisfortheexperimental
analysisofreferenceandmeaning(Hayes, 1992;Sidman, 1986). Itisimportantto
notethatifthestimulirelatedviaequivalencerelationsdidnotalsobegintoshare
)
4
i i
v
A1 3> B1 s» C1
-c- <-
A
LEGEND
^ Trained relations (A1-B1; B1-C1)
« Symmetry (B1-A1; C1-B1)
> Transitivity (A1-C1
«c_ Symmetrical Transitivity (C1—A1)
Figure 1. A schematic representation of the properties that
define an equivalence relation. The solid lines indicate trained
relations and the broken lines indicate derived relations.
5
establishedstimulusfunctionstheywouldbeoflittleuseaslaboratoryanaloguesof
symbolicrelations. Forexample,ifthewords"water,""agua,"and"paanee"
enteredintoequivalenceclasseswithoutalsobeginningtosharestimulusfunctions,
thentheirbeingequivalentwouldonlybemeaningfulintermsofthederived
conditionaldiscriminationsusedtodocumenttheequivalencerelations. Itis,
however,preciselytheobservationthatstimulirelatedviaequivalencealsobeginto
sharestimulusfunctionsthathassuggestedthatthefunctionsofthestimuliin
equivalenceexperimentsmaybelikenedtothefunctionsofsymbolsinnatural
languages(Hayes, 1992;Sidman, 1986).
Theseobservations,incombinationwiththefactthatequivalenceclass
formationhasnotyetbeenreportedwithpreverbalhumansornonhumans
(Devany,Hayes,&Nelson, 1986;Sidman,etal., 1982)but(seeSchusterman&
Kastak, 1993),haveledmanytoconcludethatequivalence-likerelationsmaybe
fundamentallyrelatedtosymbolicorlinguisticfunctioning(Hayes&Hayes, 1989;
Sidman, 1994). Ithasfurtherbeensuggestedthatresearchontheextensionof
stimulusfunctionviaequivalenceclassesmayyieldsomeinsightsabouthow
humanscometobehavesystematicallyandpredictablyinthepresenceof
circumstancesthathaveneverbeforebeenexperienced(Hayes, 1992;Sidman,
1986).
Althoughsomeresearchhasexaminedtheextensionofrespondenteliciting
functions(e.g.,Dougher,Auguston,Markham,&Greenway, 1994)andoperant
consequencefunctions(e.g.,Hayes,Kohlenberg,& Hayes, 1991),themajorityof
workinthisareahasbeenconcernedwiththetransferofdiscriminativestimulus
functions(e.g.,Auguston&Dougher, 1997;Barnes,Browne,Smeets,&Roche,
6
1995;Lazar,1977;Lazar&Kotlarchyk, 1982;Wulfert&Hayes, 1988). The
earliestexperiment explicitlyconcernedwithtransferoffunctionandstimulus
equivalencewasreportedbyLazar(1977). Adultsubjectswereaskedtopointto
eachmemberofseveralpairsofstimuliacrossrepeatedtrials. Twodistinctclasses
ofstimuli(roughly,"pointed-tofirst"and"pointed-tosecond")emergedfromthis
training. Inthenextphase,thesamestimuliservedassamplesinaconditional
discriminationtaskinwhichnovelstimuliwereintroducedascomparisonsin
reinforcedtrials. Followingthat,conditionaldiscriminationtrialswerepresentedin
whichthenovelstimuliservedassamples("incorrect"responsesduringthis
conditionwereremediatedwithdirecttraining). Finally,thesequencetestwas
re-presentedwiththenovelstimulitotestfortransferoffunction. Lazar(1977)
reportedthat2ofthe3subjectsrespondedappropriately. Thatis,thesesubjects
pointedtothenovelstimulusthatwasplacedinthe"first"classfirstandthe
"second"classsecond. Thediscriminativepropertiesofthetrainingstimulushad
thusextendedtootherstimuliinthesameequivalenceclass.
Studieshavealsoexaminedtheextensionofotherkindsofdiscriminative
functions. Catania,Home,andLowe(1989)establishedahighresponserateinthe
presenceofonestimulus(atree)andalowresponserateinthepresenceofa
differentstimulus(astar)ina5-year-oldchild. Theschedulesandstimulialternated
severaltimeswithinasessioninamultipleschedulearrangement. Inthenext
phase,thesestimuliwereusedascomparisonsinconditionaldiscriminationtrials
involvingtwonovelstimuliassamples(awormandablock). Afterseveralsessions
ofgreaterthan90%correctmatchesandconsistentratedifferencesinthemultiple
schedule,thesubjectwasre-exposedtothemultipleschedulewiththedifference