Fear Conditioned With Escapable and Inescapable Shock - Effects of a Feedback Stimulus

8/12/2019 Fear Conditioned With Escapable and Inescapable Shock - Effects of a Feedback Stimulus

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Journal of Experimental Psychology:Animal BehaviorProcesses1984, Vol. 10, No. 3,307-323C o p y r i g h t 1 9 8 4 b y t h eA m e r ic a n P s y c h o lo g i c al A s s o c i a t i o n , I n c .

Fear Conditioned With EscapableandInescapable Shock:Effects of aFeedback StimulusSusanMineka,Michael Cook,and StephanieMillerUniversity of WisconsinMadison

Four experiments compared the levelof fear conditioned with escapableversusinescapable shock. In Experiments 1 and 2, master subjects that had received 50unsignaled escapable shocks were less afraid of the situation where the shock hadoccurred than were yoked subjectsthathadreceived inescapable shocks. Comparableresults were foundinExperiments 3 and 4, which used freezingas an index offear of a discrete conditioned stimulus (CS) that had been paired with shock.Interestingly, control per se was not necessary to produce the low level offearseenin themaster subjects: Yoked groups receivingafeedback signalat the time themaster madean escape responseshoweda lowleveloffearthatwascomparabletothat of the masters and significantly less than that seen in theyoked.subjectswithout feedback. In addition, there were strong suggestions that control and feedbackexert theireffects through the same or highly similar mechanisms. Possible expla-nationsfor howcontrol and the exteroceptivefeedback signal produce this effectare discussed.

Overthepast 15yearsanenormous amountofresearch hasbeen directed toward under-standing thedifferential behavioraland phys-iological effects that stem from exposure tocontrollable as opposed to uncontrollableaversive events. The general conclusion hasbeenthat exposuretouncontrollable aversiveevents isconsiderably more stressful for theorganism than is exposure to controllableaversive events.The greater stress has beenindexed by awide rangeofbehavioraldeficitsandphysiological changes, including impairedability to learn control in subsequent tasks,passivity,lowered aggressiveness, alterationsinlevels ofcertain important neurotransmitters,ulcers,analgesia,andmany others. (See Maier&Jackson, 1979; Maier & Seligman, 1976;Mineka &Kihlstrom, 1978; Overmier, Pat-terson, &W ielciwicz, 1980; Seligman, 1975,for reviews.)

Thisresearchwassupportedbygrantsto the firstauthorfrom the University ofWisconsin Graduate School andbyGrantBNS-7823612fromtheNational Science Foun-dation.Theauthors would liketothank Robert Hendersen,TomMinor,andMike Fanselowf ortheirhelpful commentson an earlier version of this manuscript.

Requests forreprintsshould besenttoSusan Mineka,Department ofPsychology, 1202W .JohnsonSt., UniversityofWisconsin, Madison,Wisconsin 53706.

The finding in this literature on uncon-trollability that is ofspecial interest for thisarticle isthat different levelsof fear arecon-ditioned toneutral stimuli paired with escap-ableasopposedtoinescapable shock. Mowrerand Viek (1948)firstreported thisfinding offear from asenseofhelplessness, and it hassincebeen replicatedbyDesiderateandNew-man (1971),Brennan andRiccio(1975), andOsborne, M attingly,Redmond,andOsborne(1975).Inthese three most recent studiesre-searchers consistentlyfoundthat rats thatre-ceivedsignaled escapable shockssubsequentlyshowed less suppression to the conditionedstimulus(CS)in aconditioned emotionalre -sponse (CER) test thand idtheiryokedpart-nersreceivingthesame amountofinescapableshocks.Some limitationson theconclusionsas towhether suchdifferencesactuallyreflectdifferent levels of fear were, however, ap-parentin theOsborneetal.(1975)article. Inparticular,theyfound anoppositeeffectwhenusinganescape from feartaskasopposed toa CERtask.Infact,theire scapablypreshockedratslearned to escape from fear faster thandidtheir inescapably preshocked rats,andthisresultdid notappearto be asimple functionof differential activity levels. Unfortunately,Osborne et al. did not conclusively solvethisapparent discrepancy inresults when using

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8 S. M I N E K A , M. COOK AND S. MILLERthe CERtaskasopposedto theescape fromfear task as an index of fear. However, onepossibilityisthatthe inescapably preshockedanimals were showingatypical learned help-lessnessorproactive interferenceeffecton theescapefrom feartask that has an instrumentalcontingencyunlike the CER task.One purpose of the present experiments wastoprovideafurtherdemonstration that morefearis conditioned with inescapable shock byusing a third measure of fear like the CERthat does nothavean instrumental componentandthathasnotpreviously been usedinthislineofresearch. Therefore, inExperiments 1and 2 the multivariate fear assessment tech-niques ofCorriveau and Smith (1978) wereusedto assessd ifferential levelsof fear in es-capablyand inescapably preshocked rats. Withthese techniques seven interrelated measuresof fearwere usedtoassessthe subject's will-ingnessto leave a safe ledge and approach agrid floor where shock had previously oc-curred,aswellas toassesstheamount oftimethat wasspent on thegridflooroncean ap-proach responsehadbeen made. These tech-niques have previously been shown to bequite sensitive in detecting different levelsoffear following different amounts an d typesof flooding experiences following jump-upavoidance response training (Corriveau &Smith, 1978; Miller, Mineka, &Cook, 1982;M i neka , M iller,Gino, &Giencke, 1981).Thesecond issuein thepresent experimentsconcerns the importance of control per se inproducing the observed differences in fearconditionedwithescapableasopposed to in-escapable shock. To date, the results have gen-erally been interpreted in terms of the in-creased aversiveness or stressfulness of uncon-trollable shocks (e.g., Maier, Seligman, &Solomon, 1969;Seligman, Maier, & Solomon,1971).In addition, Desiderataand Newman(1971) and Brennan and Riccio (1975) dis-cussedthepossibility that inescapable shocksmay simply be more painful because of theyoked experimental design used in their ex-periments (Church, 1964).

However, a third possible explanation fortheresultsofsuchexperimentsisalsopossibleand worthy ofinvestigation.This third expla-nation stems from a theory proposed someyearsago byAverill(1973),whoargued thatthe beneficialeffectsof having control over theoffset of aversive events stemmed primarily

fromtheaddedpredictability inherentinhav-ingacontrolling response, that is,organismswith control also know when the event willterminate and havea salient marker of theensuing interval during which the aversiveevent will not occur. Although it seems unlikelythatall of thebeneficialeffectsthat derivefromcontrol stem fromthis mechanism, Starr andMineka(1977)did findevidence thatarelatedmechanism might be involved in the differ-ential levels of fearconditioned with control-lable versus uncontrollable shock.Intheir sec-ond experiment StarrandMineka foundthatyokedanimalsgivena feedback signal whenthe master animal made its escape or avoidanceresponsedid not differ from their masters inlevelsoffearconditioned to the CS, althoughyoked animals without feedback were signif-icantly moreafraidthan the other two groups.Theseresults suggest that control per se isnot necessary to observe the attenuation offear frequently seeninwell-trained avoidancelearners(cf.Kamin, Brimer, &Black, 1963;Starr&Mineka, Experiment 1).Rather, feed-back from the avoidance response itself ap-peared to be sufficient toproduce the atten-uationinyoked subjectswho had nocontrol.In addition, these results raisedthe interestingpossibility thatthe differences in fear condi-tioned with escapable versus inescapable shockmay also be due to the presence; versus absenceof feedbackrather thanto thevariableofcon-trol per se or tod ifferencesin amount of painexperienced by escapably versus inescapablyshockedsubjects.The followingexperimentswere designedin part to test this hypothesis using two dif-ferentparadigmsforassessingfear.In the firsttw oexperiments Corriveau andSmith's(1978)multivariate fear assessment techniques de-scribed earlier were used with an unsignaledescape paradigm. In Experiments 3 and 4freezingwasusedas anindexoffearin asig-naled escape paradigm wherefearwas assessedin asecond context other thanthe one inwhichfear was conditioned.

Experiment 1MethodSubjects and Apparatus

The subjects were32male albino ratsof the Fischerstrain obtained from Harlan Sprague-Dawley Company,Madison,Wisconsin. The animals were90-120days old


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EFFECTS OF CONTROL AND FEEDBACK ON FEAR 309at thetimeof theexperiment.They were housed individ-ually andmaintained on areverse 12-hrlight/12-hrdarkcycleday.Theexperimentwasconducted duringthedarkportionofthe cycle. Throughout the experiment all subjectsweremaintained onad-lib food andwater.

The apparatus consisted of two automated jump-upboxesobtained from LafayetteCompany. Ineach box a20.0 cm X11.5cmpartof onewallretracted, revealinga 12.5c m high X20.0 cm wide X 12.5c m deep ledgethat was 8.5 cm above the grid floor. The main chamberwas madeofPlexiglas(two wallsand the lid)and metal(themovable wall, the ledgecompartment,and the wallopposite the ledge). The grid floor consisted of fourteen0.48-cm stainless steel grids placed 1.6 cmapart (centerto center) to which constant current scrambled shock of0.7 mAintensity couldbedelivered.Each apparatus wasenclosed in a51.8cmhighX78.7cmwideX 40.7 cmdeepsound-attenuating chambercon-structed of/2 in,plywoodand 1 in.styrofoam witha50.5cm X29.0cmPlexiglas observation window. Inside eachofthesechambers weretwohouse-lightslocated25.5cmovertheapparatusand aspeakerf orgenerating white noisethat was also located 25.5 cm above the center of theapparatus.Foreach apparatus, a 21.0 cm X20.0 cmremovablePlexiglasbarrier could be used toconfinesubjects on theledge. The carrying/retaining boxes were plastic test cages,29.0 cm X 18.0 cm X 13.0 cm,with wood shavings onth ebottom and awire grid lid for atop.All programming of experimental events and obser-vationswascarriedout in thedarkenedexperimentalroom.W hitenoiseatapproximately6 3dB(A)wasdeliveredintotheapparatus at alltimes when subjects were in the ex-perimental room.Procedure 1A

The 16ratswere dividedintotwogroupsof 8subjectseach.Thegroupthatreceived escape training wasdesig-nated themaster-nofeedback(M-NFB)group. The secondgroup wasdesignated the yoked-no feedback (Y-NFB)groupandreceived noncontingent shocks. Experimentalchambers were counterbalanced across treatment groups.Th eexperimentwasdivided into fourphases: firstledgeexposure, escape training, second ledge exposure, and fearobservation.First ledgeexposure. Aftereach subjectwa splaced ontheledgeof itsrespective chamber, thePlexiglas barrierwas inserted, thereby blockingthesubject on the ledge.Subjects remained undisturbed on the ledge for 15m ininorderto increase familiarity with theledgeas asafeplace.Escape/yoked training. At the end of the 15 min ofledgeexposure the barriers were removed, and the movablewall waspushed forward sothat the ledgewas nowonly2.5 cm deep (not enough for the subjects to rest on). Thiswallmovement also servedtopushthesubjects onto thegridfloor.Duringthenext75 minsubjects wereexposedto aseriesof fifty0.7-mA shocks presented on a VT 90-s geometric schedule (range60-128s). Themasterrat (M-NFB) could turn offthe shock after 1 s bydepressingtheledge(the shock also terminated at 1 s if the ledge wasstilldepressedat that time from aresponse made priorto 1 s). The yoked (Y-NFB) animals received the sametemporal patternofshocksas didtheir partners; however,theirresponse manipulandumwasdisconnected. Inother

words, theresponse of the rat in theM-NFB groupde-terminedtheshock durationfor itsyoked partner.If theM-NFB rat failed to terminate the shock within 30 s, itwas terminated automatically fo rboth groups. Secondledgeexposure(timeout). After thelast escapetrial, the wall was retracted to its original position, andsubjects were again blocked on the ledge by the Plexiglasbarrier for 15min.Fear observation. The time out wasfollowed by a 1-hrassessment of thesubjects' fear of thegridfloorusingtheobservational techniquesdevelopedbyCorriveau andSmith(1978)and later used by Mineka etal.(1981),andby Miller et al.(1982).The barrier was removed, and bothM-NFBandY-NFB subjects were simultaneously observedby a trained experimenter. The seven dependent variableswere as follows:Approach latency (AL)t he time inseconds itinitiallytook thesubjectstoleavetheledgefor thegridfloor.

Safety-test latency (SL)t he time ittook the subjectsto make the initial safetytest(1-2paws or nose touchingthegridfloor). If the subject approached the grid floorwithoutasafetytest, this scorewasidenticalto theapproachlatencyscore.Number of safety tests before first approach (FST)the total number of safety teststhatoccurred before thefirst complete departure from the ledge.Totalnumber of safety tests(STT )ihe total numberofsafetyteststhatoccurredoverthecourseof the60-minsession. (This measure was not used by Corriveau andSmith.)Totalnumberofapproaches (NA)the numbero ftimesth esubject went back an d forth from th e ledge to thegrids.Timeinitiallyspent on thegrids after the first approach(FG)the total amount oftime inseconds spent on thegrids after the firstapproach and befqre the first returnto the ledge (recorded because all subjects thatapproachedthegridsatleastoncealso returnedto theledge afterthefirstapproach). Th esubjects that never left theledge re -ceiveda 0 for this measure.Totalgrid time( TG)t h etotal amountoftimein sec-onds that each subject spent on the grids during the 1-hrobservation phase.All ofthese dependent measures werehandscored bythe experimenter. Periodic reliability tests were made withasecond observer present.Theinterrater reliability checksrevealed the intraclass correlations to be over .993 for eachof the dependent variables( M = .997; cf.Tinsley& Weiss,1975).Procedure IB

Sixteenmore rats were divided into two groups of 8rats each. All phases of this experiment were identical toExperiment 1Afor theM-NFB groupgivenescape training.However,theyokedgroup, designated yoked feedback(Y-FB), received an exteroceptive feedback stimulus at theshock offset that consisted of the house-lights going offfor 3 s.Results

AsfoundbyMinekaet al.(1981), inspectionofthedatarevealed mildtosevere heteroge-neity of variance for five of seven measures


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310 S. MI N EK A, M. COOK, AND S.MILLER(except for FST and STT). In addition, allmeasureshad distributions that were severelyskewed and clearly not normal in the tails.Therefore, forallmeasuresforthis experimentand forExperiment2,ttestsandanalysesofvariance (ANOVAS)were performedon trans-formed scores. Negative reciprocal transfor-mationsoftheform 11were foundX + 10,to makethe data most amenable to A N O V Astatisticson thebasisofthree criteria (cf. Mos-teller & Tukey, 1977, chapter 5): (a) Thesetransforms reducedtheheterogeneityofvari-ance; (b) they made the distributions moresymmetric; (c) they produced a pattern wherethemeansof thetransformed scores paralleledthepatternofmediansof the rawscores. (SeeMineka etal 1981^ for further discussion.)In addition, safety testand approach latencyscores were converted to minutes before thenegativereciprocaltransformationswere madebecause of the large number of high scores(e.g.,3,600).Thedatawerealso analyzed withnonparametricstatistics,andthesame patternofresultswasfoundexcept where noted below.Experiment 1A

Escape training. Allsubjects learned theescape response very rapidly. Unfortunately,onlya cumulative record of the totalamountof shockwasavailable,and so the courseofescape learning could not be examined (butseeExperiments 3 and 4 for relevant results).The average amount of shock received was1 . 0 8 6 s pertrial (1-sminimum).Feartesting. Thettests revealed significantdifferences(p


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EFFECTS OFCONTROL ANDFEEDBACKONFEAR 311

1BTQ

Figfire 2.Meansof thetransformed,1 - [10/(X+ 10)],first grid (FG) andtotalgrid (TG) time scores for the fourgroupsofExperiments 1A and IB . (MNFB =master-nofeedbackgroup;YFB =yoked-feedback group; YNFB=yoked-no feedbackgroup.)

from feartaskthatdoes havean instrumentalcontingency.Inparticular, these results suggestthat morefearisindeed conditionedtostimulipairedwithinescapable asopposedtoescap-able shock. Failures to find this effect may bedue to the use ofindicesof fearthathaveaninstrumental contingency, thus allowing aproactive interferenceeffect fromthe inescap-ableshock to obscure such differences.The results of Experiment IBalso lend pre-liminary support to the hypothesis suggestedin the introduction that control per se maynot be thevariable ofimportanceinproducingthe different levels of fear conditioned withescapable versus inescapable shock.Inthisex-periment we found that the yoked subjectsgivenafeedback stimulus(Y-FBgroup) whenthe mastersubjectsmade their escape responseshowed levelsof fear comparable to that ofthe M-NFB group even though they had hadno control overthe shock. Thus,as in Starrand Mineka's(1977)second experiment usinganavoidance paradigm,itseems thattheaddedpredictability orfeedback inherentinmakingtheresponsemay be sufficient toproduce thereduced level of fear seen with controllableshock. However, before taking this hypothesistooseriously,wedeemeditnecessary torep-licatethe findings ofExperiments 1Aand IBusingatriadicdesign rather thanthetwo-groupdesigns of these preliminary experiments.Therefore, Experiment2 wasdesigned to do

this by having two groups yoked to the M-NFBgroup, oneY-FB group receiving feed-back when the M-NFB group responded (asin Experiment IB ) and one Y-NFB groupreceiving no such feedback (as in Exper-iment 1A).

Experiment 2Method

Subjects and ApparatusThe subjects were 36 male Fischer ratsobtainedfromHarlan Sprague-Dawley Company, Madison, Wisconsin.

Theywere90-120days old at the time of the experimentand were housed under conditions identical to thosede-scribed forExperiment 1.The apparatus consisted of the same twojump-upboxeswith their sound-attenuating chambers described in Ex-periment 1 and anadditional jump-upboxwith sound-attenuating chamber constructed at the University of Wis-consin.Inthis third jump-upbox a21.3cm X 11.0cmpartof onewallretracted revealinga 11.0c mhighX21.3cmwideX13.0cmdeep ledge thatwas 7.8 cmabovethegridfloor. Themain chamberwasmadeof Plexiglas(twowallsand the lid) and metal (the movable wall, the ledgecompartment, and the wallopposite the ledge). The grid*floor consisted of seventeen 0.2-cm stainless steel gridsplaced 1.2 cmapart (centertocenter),to which constantcurrent scrambled shock of 0.7 m A intensity could bedelivered. Although this box differed slightly from thoseused in Experiment 1, the differenceswere within 1 cmfor alldimensions. Further,a main effect forboxes wasnever found to be significant. The sound-attenuatingchamber,Plexiglas barrier,andcarrying/retainingboxwereidenticaltothoseinExperiment 1.Procedure

There were two groups comparable to those in Exper-iment 1A (M-NFB and Y-NFB) and a third group com-parable to the Y-FB group in Experiment IB .Thus, themaster controlledtheshock durationforboth yoked groups,one ofwhichreceivedthelights-offfeedbackstimulus.Thegroupswerelabeled M-NFB, Y-NFB,andY-FB.The M-NFB groupwas run in one of the twoidentical Lafayetteboxes but not in the third box because the ledge tensionwasslightlydifferent inthat box.The twoyoked groupswererun randomly in all three boxes.

ResultsEscape Training

Allsubjects learnedtheescape response veryrapidlyas inExperiment 1.Theaverage shockduration per trial was 1.15s.Fear Testing

Thedata revealed heterogeneityandskewed-ness similar to that in Experiments 1A and


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312 S. M I N E K A , M. COOK, AND S. MILLERIB .Therefore, the same negative reciprocaltransformationsf1 - , .\were employedx + 10;here. A N O V A S showed significant differences(ps


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EFFECTS OF CONTROL AND FEEDBACK ON FEAR

prisingthatno group differences were foundwiththis measure in Experiment 2. By con-trast, however, approach latencyand thetotalnumberofapproachesaregenerally sensitivemeasures,and so thefailureto find significantgroup differenceswith these measures in Ex-periment 2 is somewhat puzzling and has noready explanation.Nevertheless,thesimilar pattern of resultsfor the other three measures of fear in Ex-periments 1 and 2 suggests that less fear isindeed conditionedwithescapable thanwithinescapable shock and thatcontrol per se isnotnecessarytoproduce this effect. Instead,mimicking the feedback that comes frommakinganescape responsebydelivering anexteroceptive feedback signal to yoked subjects(Y-FBgroups) seems to be sufficient to pro-duce the lowered level offearcharacteristicofsubjectsthatactuallydohavecontrol.It shouldbe noted, however, that theparadigm used toproducetheeffectsseeninExperiments1 and2isconsiderably different fromthe paradigmsusedin theprevious experimentsonfear con-ditioned with escapable versus inescapableshock. Not only were different measures offear used than inprevious experiments butalso the shocks were unsignaled in our ex-periments, and sofearof the entire situation(grid floor and surrounding area) was beingassessed in the fear test. In all other experi-mentsinthisarea, fearwasconditioned to adiscrete CS, and fearof that CS was then as-sessedineitherthesameor ad ifferent context.Thus, the possibility exists that the effectswehave seen ofadding a feedback stimulus toour yoked subjects are somehow limited toour particular paradigm using unsignaledshockand/or Corriveau and Smith's fearas-sessment techniques.

Therefore, Experiment 3 was designed withthe goal of replicating the sameeffects seen inExperiments1 and 2 in aparadigm more likethat usedinprevious experimentsin thisarea.Theescape/yoked trainingwasstill carriedoutin the modified jump-up apparatus used inExperiments1 and 2, but the shocks were nowpreceded by a 20-sauditory CS. In the feartesting phase, fearof the CS was assessed ina context different from where it bad beenconditioned. Freezing duringthe CS andpost-CSperiodwasusedas theindexoffearratherthan atraditional CERtask. Asreported by

BoutonandBolles(1979)andBollesandCol-lier (1976), freezing can be a highly reliableindexoffearwhen the observations are madebywell-trained observers. In fact,in our lab-oratory we have found it to be preferable toCER testingforthree reasons.First,it ismorecost efficientbecause of the obviation of 5-7daysofoperantbarpresspretraining; second,dataare not frequently loston atestday be-causetheoperant baselinehasbeen destroyedafter the presentation of several fear-elicitingCSs;third,wehave found freezingto bemoresensitiveindetecting groupdifferences follow-ing avariety ofmanipulations than are thetraditional CER techniques we have used pre-viously (e.g.,Mineka &Gino, 1980;Starr&Mineka, 1977).

Experiment3Method

Subjects and ApparatusThesubjects were36male albino ratsof the Fischerstrain obtained from Harlan Sprague-Dawley Company,Madison, Wisconsin. The animalswere90-130days old

at the time of the experiment and were housed underconditions identicaltothose described forExperiment 1.The escape training phaseof the experiment utilizedth ethree jump-up boxes and their sound-attenuating en-closuresthatweredescribedinExperiment2. Themovablewallof thejump-up boxeswasalwayskeptin the forwardposition leavinga 2.5-cm deep ledge. The enclosures weremodified in the followingmanner: ASonalert(Model SC628) wasmounted3.5 cmabovethecenterof theceilingof the twojump-up boxes obtained from LafayetteCom-panyand 2 cmabovethecenterof theceilingof the boxconstructed at the Universityof WisconsinMadison.(Thisslightdifferencewas necessary becauseofthe slightlydifferent shapeandsizeof thethird jump-up box.) EachSonalert was capable of delivering a 2900-Hz tone (inter-rupted4.5 times/sand on for 70% of agiven second) ata noise level of 95dB(A) against a background of 63dB(A). This tone served as the CS. A0.6-mA scrambledshock,delivered by a constant current source to the gridfloor,servedas the unconditioned stimulus (US).Additionally,C Shabituationand feartesting were con-ducted in three identicalGerbrandsoperant conditioningchambers. Each measured 22 cm high X 22.5 cmwide X 19.5cm deep and had an inoperative responseleverlocated to the left of arecessed food magazine.ASonalert (ModelSC628)wasmounted3.5 cmabovethecenterof theceilingineach conditioning chamber, deliv-eringa2900-Hz tone (interrupted 4.5times/sand on for70% of agivensecond)at anoise levelof 96d B(A)againsta background of 56 dB(A). Each operant chamberwasenclosed in a 61 cm high X 68 cmwide X 55 cm deepsound-attenuating chamber obtained from IndustrialAcoustics Company.A 29 cmhighX44c mlong one-waymirror located on the front of each sound-attenuating


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314 S. M I N E K A , M . COOK, AND S,MILLERchamber allowed observation of the subjects by an ex-perimenter situated within the darkened experimentalroom.A 40-Wlight bulb, mounted withinatranslucentpanel on the interior ceiling ofeach sound-attenuatingchamber, 7 cmabovetheceilingof the operantchamber,served as illumination. A 100-mA, 28-V, red miniaturelightbulb, also mountedon the front of the sound-atten-uating chamber(sothatit wasunobservableby thesubjectwithin theoperant chamber), servedas atimingcue tothe observer situated near theenclosure(seeProceduresection).Programming of experimental events concerningtheoperant conditioning chamberswasdone automaticallyby relayequipment located in anadjacent room.Procedure

Three groupsofsubjects wererunwithn= 12ineacht rea tmentgroup. One to 2 daysprior to the first day ofexperimentationallsubjectswerebrieflyhandledandtheirtailsmarkedsothat theexperimenter could distinguishbetween them. The experiment was divided into threephases over the courseof 5days.Habituation. On Day 1each subjectwasplaced in anoperant chamber andallowed approximately 3-5 min tohabituateto itbeforethe firsttonewaspresented. Atotalofsixteen20-stones were presented on avariable time(VT) 4-min geometric schedule (range:176-317s). Thisphaseallowedfor the habituation of any unconditionedproperties of the tone to occur.Duringeach trial (presentation of atone)the experi-menterobserved and recorded the subject's behavior 12times at 5-s intervals using a point-sampling technique.Ofthe 12point-sample observations,4wererecorded dur-ingthe 20 simmediately preceding onsetof thetone(des-ignated PeriodA), 4 duringthe 20 s the tonewas on eriodB), and the last 4 during the 20 s immediatelyfollowingthe offset of thetone(Period C). Theonset ofthe redminiature lamp bulb (mounted on the front ofthesound-attenuating enclosure) servedto cue theobserverastowhenthebehavior samplewas to betakenand re-corded. The subject's behavior wasdivided into one offourmutually exclusive categories: (a) freezing absenceofskeletal movement exceptforthat due to respirationor minimal vibrassae movement, (b) sleepingdefinedidentically to freezingwiththeadditional requirement thatthe subject's eyesbe completely or almost completelyclosed,(c)groomingany licking,scratching,orrubbingofanypartof thebody,and (d) otherallbehavior fallingoutsideof thethree previous categories. Forpurposesofthepresent experiment onlythefreezingcategory,wascon-sideredto be ofinterest,and soonlytheresults from thefreezingdataare presented.Escape training. On Day 2,approximately 24 hrfol-lowinghabituation, escape trainingwasinitiated.Subjectswere run in triads, each memberof the triad-randomlyassigned to one of three treatment groups, master-nofeedback(M-NFB), yoked-feedback (Y-FB),andyoked-no feedback(Y-NFB),Afterbeing placedon thegridfloor,thesubjectsremained undisturbed for 30min. They,werethenexposed to 50 shock trials presented on a VT60-sgeometric schedule (range:30-106s).Eachtrialconsistedofa20-s toneCSfollowedby theonsetofshock deliveredto the grids. The shock was programmed to last a minimumof 1 s before it could beterminated by a response by

subjectsin theM-NFBgroup.Aresponse resulted ihthecotermination of the CS and US(after the 1-sminimumshock duration). Shocks that were not terminated by aresponse within30 s followingtheir onset were automat-icallyterminatedby theprogramming equipment. Subjectsin the Y-NFBgroup received identical exposure to CSsand USs as their masters but had no control over CS orUStermination. Subjects in the Y-FB;group received a3-slight-off feedbackstimuluswhentheir master respondedaswellasidentical exposureto the CSs andUSs.Fear testing. OneachofDays3-5,at approximately24-hrintervals, each subjectwasreintroducedto the op-erantchamberin whichit hadbeen habituated.Oneachday afterapproximately7min,the firsttonewaspresented.OnDays3 and 4 atotalofeight 20-s tones were presentedon a VT 7-min geometric schedule(range: 390-451s),whereas on Day 5onlyfour20-s tones were presented(onthe same schedule). Further, the same point-samplingtechniqueemployed during habituationwasused duringTrials 1-4 on Days 3-5 (i.e.,behavior was not observed/recorded for the last fourtrialson Days 3 and 4).Three experimenters were involvedin theobservationof thesubjects' behavior during habituationandfeartesting;therefore, some measureofinterrater reliabilitywasnec-essary.Becauseoflimitationsofspacein theexperimentalroom, onlytwoobservers couldbepresent duringagivenreliability-assessment session. Forthis reasonFleiss'gen-eralization ofCohen's statistic,kappa,wasusedtodeter-minecategory agreement in thecase where subjectsareobserved and rated by different pairs of raters (Cohen,I960;Fleiss, 1971). In the present case, the reliabilitysessions, encompassing 440 individual 'point-sampleob-servations and involvingall raters, resulted in = .91.W he nt he freezingcategoryw asconsidered aloneK= .91.Bothresultsaresignificant,p


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EFFECTSOFCONTROLANDFEEDBACKONFEAR 3 5

PERIOD A PERIODS PERIODC

I T I 2 3 2 3 2 3DAYS

Figure5.Meannumberoffreezingresponsesper d ay foreachof thethree groupsof E xperiment 3,summedacrossthetest trialsofeach day, separatelyforPeriodsA ,.B,and C.(MNFB=master-no feedbackgroup;Y FB = yoked-feedback group; YNFB =yoked-no feedback group; PeriodA- 20 s beforetone onset;Period B = 20 sduring tone; PeriodC = 20 safter tone offset.)

peatedmeasuresANOVA,withfivetrialsineachof1.0blocks.Theanalysis revealedasignificanteffect of the repeated measure, F(9, 99) =25.94,p


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316 S. M I N E K A , M. COOK, AND S. MILLER1.42.Duncan's post hoc comparison's revealedthat the Y-NFB group showed significantlymore freezingthandid the M-NFB andY-FBgroupsduring PeriodsB and C, but thelattertwogroupsdid not differ significantly.In ad-dition, analysisofsimple main effectsfor pe-riod and Duncan's post hoc comparisons re-vealedthatallthreegroups showedelevationsin freezingduring both PeriodsB and Coverthat seen in Period A, Fs(2, 22) ;> 12.17,ps


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EFFECTSOFCONTROLANDFEEDBACKONFEAR 7Procedure

Theprocedurewasidenticaltothat describedfor Ex-periment 3except thatthe subjects in themaster group(M-FB)received a 3-slights-off feedback stimuluseverytimetheymadea successful escape response.One yokedgroup (Y-FB) also received this feedback stimulus,andone yoked group(Y-NFB)did not. Interrater reliabilitywas verycomparabletothat forExperiment3.

ResultsandDiscussionHabituation

The habituation data were analyzed in a 3(group) X 3(period) mixed-design A N O V A asforExperiment3. Theanalysis revealedasig-nificantmaineffectforperiod,F(2,66)=9.45,p


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318 S. M I N E K A , M. COOK, AND S. MILLERExperiment X Period interaction,F(2, 132),ps


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EFFECTSOFCONTROLANDFEEDBACKONFEAR 319slightly different, withthe M-NFB groupofExperiment3 showing longer latencies at theoutsetoftrainingandslightly shorterlatenciesat the end oftraining than the M-FBgroupofExperiment4.However, because there werenooveralldifferences inamountofshockre-ceived in the two experiments and becauselevels of freezing did not differ between ex-perimentsduring Period A of fear testing,itseemssafetodrawatleast some tentative con-clusionsregarding the cross-experiment com-parisons. In particular, these results are con-sistent withthehypothesis that feedbackandcontrolexert theireffectsthroughthesameorhighly similar mechanisms. Because mastersubjectswith feedback showed levelsof fearthatwereverycomparabletothose shownbymaster subjects without feedback, it does notappear to be the case that exteroceptive feed-backexertsaneffectonreducingfearoverandabovethat producedby anescape response.1If exteroceptive feedbackwereproducing itseffect on reducing fear through a differentmechanismthan doesanescape response, thenonewould expect theretohave been additiveeffects, that is, M-FB subjects would showlowerlevelsoffreezingthan M ^ NFBsubjects.

GeneralDiscussionTheresultsof all four experiments concurinsupporting earlier conclusions regardingtheamountoffearthatisconditioned toneutralstimulipaired with escapable versusinescap-ableshock. Using both signaledandunsignaledshockandseveraldifferent indicesoffear,we

haveconsistentlyfoundlessfearingroupsre-ceiving escapable as opposed to inescapableshock. However, just asconsistently wehavealsofoundthat controlper se is notnecessarytoproducethelower leveloffear characteristicof the groups with control. Indeed, simplymimickingthe response of the master subjectbypresentation of anexteroceptivefeedbacksignal is sufficient toproduce the lower levelof fearingroups that havenocontrol overtheshock.Thusitappears that feedback doesnothavetoderivefromaresponse contingencyinorder to be effective in attenuating fear (seealso Starr & Mineka, 1977; Morris, 1975;Weisman &Litner, 1972). Instead, it seemsthattheroleoffeedback in reducing fearde-rivesfrom itsPavlovian (i.e.,temporal)rela-

tionship to the CS and the US ratherthanfrom its relation to the response per se. Itshouldbenoted that this conclusioniscontraryto that drawn by Weiss (1971) and Bolles(1971),whoargued thatthe efficacy of feed-back inreducing stressorfacilitating avoidancelearningmust stemfromtheintrinsic relationbetweenfeedbackandperformingaresponse,thatis, theresponse must inform theanimalthatit haseffectedachangein itsenvironment.Theinteresting question that remains is, ofcourse, through what possible mechanismproprioceptive or exteroceptive feedbackre-sults in lowered levelsof fear. One possiblemechanism suggestedby Starr and Mineka(1977)fortheir related resultsin anavoidancecontext isthata feedbackstimulus (FS)mayreducetheleveloffearconditionedto the CSby reducingthefunctional intensityof the US.Inparticular,the FS(andtheescape response)may partially inhibit the fear reaction thatwouldotherwise persist forsome seconds fol-lowing the termination of the US.Althoughsuch anexplanation wouldnot bewholly con-sistentwithstimulus-stimulus(S-S) viewsofconditioning that stress the importance of theUSand not the unconditioned response (UR)inconditioning,itsviability must awaitfurtherresearch designedto directly assess itsplau-sibility. For example, psychophysiological as-sessment of the fear reaction in M-NFB,Y-FB, and Y-NFB groups could be used todetermine whetherthepresence offeedback,eitherin the formof anescape responseor anexteroceptiveFS,doesin fact reduce the in-tensityand/orduration of the unconditionedresponse to the US. Evidence that such re-duction in the UR does indeed occur wouldbeconsistent with this explanation, althoughitwouldnot initself constitute definitive sup-portforthishypothesis.Asecond possible explanationfor howfeed-backreducesthelevelof fearconditioned tothe CS derives from the Rescorla^Wagnermodel(1972).Let us firstconsider Experiment3,where there arethree elementsof the sit-

1Itshouldbenoted that this lackof adifferencebetweentheM-FBandM-NFB groupswas not simplydue to afloor effect. As can beseenin Figures5 and 6,levelsoffreezingduring PeriodsB and C were sufficientlyelevatedsothat anypossible groupdifferences should havebeendetectable.


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320 S. M I N E K A , M. COOK, AND S. M I L L E Ruation that mustbeaccountedfor:theCS,thebackground cues, and the FS or escape re-sponse (for Groups Y-FB and M-NFB, re -spectively). If one considers that the back-ground cues competebothw ith the FS or es-cape responseforinhibitory strengthandwiththe C S for exc itatory s trength, the n a possibleaccount of our results in Experiment 3emerges. For Groups M -NFB and Y-FB theescape response andexteroceptive FS,respec-tively,should acquire strong inhibitory powerbecause they areexcellent predictors of fairlylong shock-free intervals. This would reducethe amount of inhibitory power that couldaccrueto thebackground cuesin theintertrialintervalsforthose groupsbycomparison withthe amount of inhibitory power that couldaccrueto thebackground duringtheintertrialinterval (ITI) for Group Y-NFB. W hen onethenconsidersinturnthattheamountofcon-ditioning that can accrueto the CSon a giventrial is greater the lower the e xcitatory strengthofthec ompeting background cues present onthat conditioning trial, then the higher levelof fearof the CS in the Y-NFB groups makessense.Bec ause the background cues are moreinhibitory(or at least lessexcitatory)for theY-NFBgroups,theasymptoteofconditioningto the CSwill be higher for this group. Forthe othertw ogroups, M -NFB and Y-FB, thebackground cues are less inhibitory (or moreexcitatory), and so compete more effectivelywith the CS fore xcitatory power, resulting ina lower asymptote of conditioning to the CS.A parallel explanation of the results of Ex-periment 4 can also be developed along thesamelines w heretheprimarydifference isthateither the proprioceptive feedback from theescaperesponseand/ortheexteroceptivefeed-back signal would be acquiring inhibitorypower.Thev iabilityofthis explanationfor the re-sults ofE xperiments 3 and 4 in terms of theRescorla-Wagnermodel could be assessed bytesting the three groups for their fear of thebackground c ues using Corriveau and Smith'sfearassessment techniquesas inE xperiments1 and 2. If this explanation is correct, onewould predict that fear of the backgroundwould begreater in Groups M-NFB, M-FB,and Y -FB thaninGroup Y-NFB(an outcomeopposite to that obtained in Experiments 1and 2,whereno CS wasinvolve d).Andindeed ,there are two recent experiments in the lit-

erature thatareconsistent w ith this prediction.Fanselow (1980)foundthatratsdeve loped anaversion for acontext inwhich they receiveda CS that was negatively correlated with shockas compared to contexts in which they receivedeitherasignal thatw asuncorrelatedwith shockorasignal that waspositively correlated withshock. Inother words,whenaCSispresentand acquires s trong inhibitory power, thereisevidence that the background or contextualcuesbecome more excitatory than when thereis no CS- (or CS+). In addition, Pattersonand Ov ermier (1981) showed thata contextualcue that was present during inhibitory fearconditioning became excitatory as demon-strated by its effect on increasingthe rate\ofongoing Sidman avoidance responding in adifferent context.Bycontrast,ac ontextualc uethat was present during excitatory fear con-ditioning did not become excitatory whentested in the Sidman avoidance context. Insum,although the resultsofthesetw oexper-iments do not provide definitive support fo rthe explanation of our results based on theRescorla-W agner m odel because they useddif-ferent parameters and were aimed at exam-iningd ifferent issues, theyare consistent withthisexplanationandprovide supportforsomeof its basic assumptions.Although theRescorla-Wagner model ap -pears to provide a plausible explanation forwhy the Y-NFB groups showed higher levelsof fearof the CSthandid the M-NFB, M-FB,and Y-FB groups in Experiments 3 and 4, itdoes not provideas ready an explanation fortheresultsofE xperiments1 and 2,which usedunsignaled shocks and tested for fear of thecontext directly. Bec ause there w as noexplicitCS to compete directly with the backgroundcontextual cues for excitatory power,it doesnot seemasobvioushow thepresenceoffeed-back (eitherin theformof anescape responseor a FS) should result in less fear being con-ditioned to the context. In fact, one mightevenpredicttheopposite resultif one considerswhathappens to the s trength of the contextualcues for the different groups of Experiments1 and 2d uringthe ITI.If it ispresumed thatthe contextual cues gain exc itatory strengthduring the shock periods and lose it duringtheITIs, then one might expect the amountof lossofe xcitatory power during the ITI tobe afunctionof how much competition thereis for inhibitory power. Because the M-NFB


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EFFECTS OF CONTROL AND FEEDBACK ON FEAR 321and Y-FBgroups have inhibitory power ac-cruing to the feedback (escape response or FS).onevery trial, the feedback should competewith thecontextual cuesforlossofexcitatorypower during the ITI. If loss of excitatorypowerduring the ITI is less for these groupsthanforgroupY-NFB,thenonemight expectthat cumulative gains in excitatory power tothe context during the shock trials to begreaterfor these groupsthan for the Y-NFB group,insteadoflessas wasactually found.Athird possible accountofthese resultswasalso first proposed by Starr and Mineka (1977).ForGroups M-NFB, M-FB, and Y-FB as thefeedback acquires fear inhibitory properties,a process of counterconditioning may occurthat reduces fearof the CS.Because thereisno powerful inhibitor of fear for GroupY-NFB, the possibility of such countercon-ditioningdoesnotexistforthisgroup,and sofear of the CSremains higher. Although weknowof no evidence supporting the possibilityof such counterconditioning in sequentialcompound conditioning situations, it doesseem like a viable alternative. However, be-cause feedback stimuli take longer to acquirefear inhibitory properties thando CSs to ac-quire fear excitatory properties (cf. Rescorla&W agner, 1972),this possibility seemsto re-quire that if fear had been assessed in ourgroups at anearlier stage, such group differ-ences would not have emerged and theM-NFB arid Y-FB groups would have beenmorefearful of the CSearlierin conditioningthanthey wereafter 50trials.A fourth possible account of our resultsbased on Wagner's (1976, 1978) short-termmemory modelwasmentioned briefly in thediscussion ofExperiment3.Accordingtothismodelit is possible that the feedback stimuliand/or theescape response disrupt rehearsalof the CS-US association for the M-NFB,M-FB,and Y-FB groups. The expected resultofsuch disruption in rehearsal would be theattainment of a lower asymptote of condi-tioningforthese groups than for theY-NFBgroups. This account would not require thefeedback stimulus or the escape response tobecome inhibitory. Therefore, further exper-imentsdesigned to assess whether they do be-come inhibitory wouldbe a firststepintestingbetween these alternative hypotheses.Althoughthesefirst four possible accountsof our results all assume that less fear was

present in the M-NFB, M-FB, and Y-FBgroups at the end of the conditioning phase,a fifth possible account stems from the pos-sibility thatourresults primarily demonstratea different rate of extinction of fear in thethree groups in the fear testing phase. Thisaccount stemsfromthe observationthattherearemore changesfrom the fear conditioningto the fear testing phasefor the M-NFB,M-FB, and Y-FB groups than for the Y-NFBgroups. For the M-NFB and M-FB groups thepresence of the ledge and the possibility ofmakinganescape responseare notpresentatallin Experiment 3 and 4, and access to theledge from a position that would allow theescape responseto bemadewas not possiblein Experiments 1 and 2 until an approachresponse to thegridshadalready been made.Similarly,for the Y-FB groupsof all fourex-periments,theabsenceof the feedback stim-ulus in thefeartesting phasemayhave allowedfor an easy discrimination between the twophasesto havebeen formed.In fact,one wayof conceptualizing the elements of the con-ditioning paradigmfor theY-FB groupsis tosay that they had a compound US consistingofshockplusan FS;bothelementsof the UScompound were gonein thefeartesting phase.By contrast,theY-NFB groupshadrelativelylesschangefrom the fear conditioning to thefeartesting phases because theydid not loseanFS or access to an escape response. Thusaccording to this account, there is greater dis-confirmation ofpreviously learned expectan-cies duringthe feartesting phase for the M-NFB,M-FB,andY-FB groups thanfor the Y-NFBgroups.Inother words, havingcontrolin the form of an escape response, and/oradded predictability by virtue of having an FS,may notresultinless conditioningoffearperse, but rather may make the organism moresensitivetochangesin environmental contin-gencieswhen the situation changes. As a result,fears once acquired may be givenup morequickly whentheoriginal contingencies havechanged.It should be noted that according to thislast account the groups should not differ attheoutsetof thefeartesting phase,butratherdifferences should emerge overthe courseoftesting. Unfortunately, an assessment ofthispossibilityf orExperiments1 and 2 is notfea-siblebecause fear testing occurred continu-ously overa 1-hr period and no discrete CS


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322 S. MI N EK A, M . COOK, AND S. MILLERwas employed. For Experiments 3 and 4, thisaccount would predict that thegroups wouldnot differon the first fewtrialsof extinction.In order to check thispossibility, Duncan'spost hoccomparisons were used to contrastthelevelsof thegroups duringthe CS for thefirsttwoextinction trialsofboth Experiments3and 4. InExperiment3 theM-NFBand Y-FB groups showed significantly lowerlevelsoffreezingthan the Y-NFB group byPeriodsBand C ofTrial 1 andduring PeriodB ofTrial2.InExperiment4this same patternofgroupdifferencesexistedforPeriodB ofboth Trials1and 2. ForPeriodC ofExperiment 4onlythe Y-FB group showed significantly lowerfreezing than the Y-NFB group on Trial 1;both the Y-FB and M-FB groups displayedlowerfree zing levelsthandid theY-NFB groupduringPeriod C of Trial 2. In sum, the resultsof Experiments3 and 4suggestthatthe dif-ferentialrateoffear extinction accountis notviable.Asisevident from theprevious discussion,itis notpossibleatpresentto becertainwhichofthe fourmechanisms considered iscorrectinaccountingfor ourresults. Nevertheless,webelieveour results are important in highlight-ingthe importance of two issues. First, theyraise some question aboutthe validityof theconclusions of the hundreds of experimentsconducted over the past. 15 years or sothathavecompared theeffectsofcontrollable ver-sus uncontrollable shock on a variety of de-pendent variables (see Maier&Jackson, 1979;Maier&Seligman, 1976, forrecentreviews).In general, such experiments have assumedthatthe use of ayoked control design suchasthatemployed with our M-NFB and Y-NFBgroupsissufficient todraw conclusions abouttheeffectsofcontrolandlackofcontrol. How-ever,our results suggest that at least some oftheeffects that have been attributed to con-trol mightinfacthave been attributed to theadded predictability or feedback that stemsfrom having control. In other words,ifsuchexperimentshadincluded groups comparableto our Y-FB groups, they might have foundthat some of their effectsattributed to controlper seweremistakenly interpreted. Inkeepingwiththis suggestion, several yearsagoAltenor,Volpicelli, and Ehrman (in press) reportedseveral failuresto replicate the basic learnedhelplessnessorproactive interferenceeffectin

ratsthathad been treated similarly to our Y-FB groups,thatis,thathadreceived inescap-able shocks followed by feedback stimuli inthe pretreatment phase. ThuSi although itseems unlikely that all the effects that havebeen attributed to control per se really wouldreduce to the effects of added feedback,ourresultsandthose ofAltenoretal.dosuggestthatcontrolsforthis possibility shouldbe in-cludedinmoreexperiments inthisarea in thefuture.The second issue highlighted by our resultsconcernstheimportanceofexaminingthe dy-namicsoffearconditioning inmore complexcontexts than those in which it has traditionallybeen examined. Most conclusions about thedynamicsof Pavlovianconditioning have beenderived fromtraditionalPavlovian paradigmswherethesubjecthas nocontrol overthe US(andno feedback aboutUS offset).However,manyof theeveryday events where Pavlovianconditioning occurs do involve situationswheresubjects have somecontrolover the USand/or some feedback that the US has ter-minatedandwillnothappen againfor awhile.Asseenin theprevious experiments, such fac-tors mayplayan important role in how muchfear is conditioned to neutral events pairedwith the US and/or how quickly such fear,once acquired, will extinguish once the situ-ation has changed slightly.

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ReceivedJuly 11, 1983Revision received January25 1984

Fear Conditioned With Escapable and Inescapable Shock - Effects of a Feedback Stimulus

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