226-243 Abstraction of Temporal Attributes

7/30/2019 226-243 Abstraction of Temporal Attributes.

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Journal of Experimental Psychology:A n i m a l Behavior Processes1982, Vol. 8, No. 3, 226-243Copyright 1982 by the American Psychological Association, Inc.0097-7403/82/0803-0226S00.75

Abstraction of Temporal AttributesWarren H. Meek and Russell M. ChurchBrown University

Cross-modal transfer of classification rules fo r temporal intervals w as demon-strated in four experiments. In Experiment 1, rats learned a temporal discrim-ina t ion between a 2-sec and an 8-sec signal in one modality (vision or audition).There was positive transfer to a temporal discrimination between a 2-sec andan 8-sec signal in the other modality when the response rule was maintained,and negative transfer when the response rule was reversed. Experiment 2 dem-onstrated positive cross-modal transfer in a temporal generalization procedure.Experiment 3 demonstrated cross-modal transfer of both duration arid temporallocation in a procedure in which rats were exposed to three successive signaldurations. Experiment 4 demonstrated cross-modal transfer of both duration andtemporal order in a procedure in which rats were exposed to simultaneouslypresented signal durations, one auditory and one visual. The conclusion is thatrats can abstract temporal attributes from modality-specific aspects of a signal.

Some animal information processing m aybe mediated by modali ty-specific systemst h a t are relatively independent. Other pro-cessing m ay disregard the specific qualitiesof a sense modal i ty (e.g., audition, vision)in favor of a higher level analysis of non-specific components. This involves, in part,the abstraction from the stimulus of certainbasic attributes common to all stimuli, e.g.,dura t ion , intensity, location, and number.There are m a n y examples of sensoryequivalence in h u m a n subjects in which dif-ferent stimulus energies (e.g., acoustical,chemical , and radiant) can carry the sames t imulus information and control the sameresponse (e.g., Freides, 1974). Althoughsome of these cross-modal equivalences can-not be due to verbal coding since they arefound in infan t s , languagema y be influent ialin m a n y cases of h u m a n cross-modal t r ans fe r(e.g., Blank & Bridger, 1964; B r y a n t , Jones,Claxton, & Perkins, 1972; Koen, 1971).The evidence for cross-modal perfor-

This investigation w as supported by National ScienceFoundation G ran t BNS 79-04792. A report based onthis work w as presented at the Third Harvard Sym-posium on Quanti tative Analysis of Behavior:Acquisi-t ion, Cambridge, Massachuse t t s , June 1980. The au-thors thank Fariba Komeily-Zadeh for her assistancein conducting the experiments .Requests for reprints should be sent to Warren H .Meek, Depar tment of Psychology, Brown Univers i ty ,Providence, Rhode Island 02912.

mance in animals comes primarily fromt r ans fe r studies in which a specific changeof performance trained to some attribute ofon e sense modality is immediately evidentdur ing testing to the same attribute of an-other sense modality. Although cross-modalequivalence in animals has been a muchstudied topic, relatively few investigatorshave reported successful cross^modal trans-fer (e.g., Ettlinger, 1977; MacDonall &Marcucella , 1976; Over & Mackintosh,1969; Seraganian & Popova, 1976; Ward,Silver, & Frank, 1976; Yeterian, Waters,& Wilson, 1976). Church and Meek (inpress) reviewed the relevant literature andconcluded that it is uncertain whether anyexperiment has unambiguously demon-s t ra ted cross-modal t r ans fe r in animals. Theresults from all of the studies examined m aybe accounted for in terms of mediationby experimenter-controlled bridging stimuliwhich are present during both training andt ransfer testing.Our interest in this study was to determineunequivocally whether rats are capable ofabstracting temporal attributes from visualand auditory stimuli. The proposal is thatstimulus information about such basic stim-ulus attributes as duration, intensity, loca-tion, and number may be identical whens t imulus modalities are different.A simple discrete-trial choice procedurew as used in Experiment 1 to demonstrate the

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ABSTRACTION OF TEMPORAL ATTRIBUTES 227cross-modal tran sfer of dura tion betw eenvision and audition. To extend the generalityof the results, we used the basic design ofExperiment 1 again in Experiment 2 w i tha temporal generalization procedure. In Ex-periment 3, rats w ere exposed to three suc-cessive signal durations and classified thesequence according to a complex combina-tion rule. A cross-modal test w as employedto demonstrate the abstraction of temporallocation as we l l as durat ion. In Experiment4, rats w ere exposed to s imul taneously pre-sented signal durations, one auditory andon e visual. A cross-modal test was then em-ployed to demons t ra te the abstraction oftemporal order as wel l as dura t ion . In over-view, these experiments focus on durationas a basic attribute. The results indicate thatanim als that have learned a particular tem-poral discrimination in one modality canabstract the temporal at tributes from themodality-specific aspects of the signal.

Experiment 1:Simple Choice Discrimination(Transfer of Signal Durat ion)In this experim ent a discrete-trials choiceprocedure w as used to measu re any cross-m odal tran sfe r of specific learning betw eenvision and audition. Rats were first trainedto classify the duration of a signal in onemodal i ty as shor t (left response) or long(right response) wi th a procedure that leadsto rapid temporal discr iminat ion learning(e.g., Church & D eluty, 1977; Maricq, Rob-

erts, & Church, 1981). Follow ing this train-ing wi th signals in one modality, animalsw ere ret rained w i th s ignals in a differentmodality (vision or audition). In order toobtain a sensitive indication of cross-modalt ransfer , half of the anima l s w ere g iven non-reversal cross-modal re t raining w i th s ignalsin the new modality (i.e., reinforcement ofa left response follow ing a short signal andreinforcement of a right response follow inga long signal), and half of the animal s weregiven reversal cross-modal retraining wi t hsignals in the new m odali ty (i.e., reinforce-m ent of a left response following a long sig-nal and reinforcement of a right responsefollowing a short signal). This same designhas been used by others (e.g., Over & Mack-

in tosh, 1969; Wilson & Shaffer, 1963). Ifthere is cross-m odal t rans fer of the at t r ibuteof duration from on e modality to another,the percentage of correct responses of thenonreversal group would be above chance(50%), and the percentage of correct re-sponses of the reversal group w ould be belowchance.The exper iment employed random-dura-tion intertrial intervals and a signal-omissiontes t, s ince prev ious w ork has show n tha tf ixed-durat ion inter t r ial in tervals m ay p a r -tially account for apparent cross-modalt ransfer (Meek & Church, in press). Threefinal t es t day s w ere included to determinethe extent to which the classifications w ereindependent of modality.Method

Subjects and ApparatusThe subjects were 20 experimentally naive male al-bino N o r w a y rats (Charles River CD ), about 10 mo oldwhen th e exper iment began. Anim als w ere individuallyhoused in m etal cages ( W ah m an n M fg. Co., Baltim ore,Mary land) in which w a t e r w as continuously available.The rats w ere fed a daily ration of about 15 g of Charles

River Rat Formula mixed w i t h w ate r immedia tel y afterth e daily session. A light/dark cycle of 16:8 hr wasmaintained in the anim al colony. A ll te s t ing w as con-ducted dur ing th e l ight phas e of the cycle.The rats w orked in 10 sim ilar lever boxes (23 X 20 X22 cm ). Noyes Precision food pellets (45 mg) were de -livered through an opening in the front wal l to a foodcup. A glass w a t e r bottle h u n g from th e back wa l l ofth e chamber. Each bo x contained tw o retractable stain-less steel levers, one on each side of the food cup. Thelevers in Boxes 1-6 were 1.6 X 4.6 cm, located 3.8 cmabove the grid floor (Gerbrands Model 6311). The leversin Boxes 7-10 w ere 2.5 X 5.0 cm, located 5.0 em abovethe floor (BRS/LVE Model 123-07). Each lever boxw as housed in a large insulation-board chamber de -signed to minimize outside light or sound. Six boxes hada 7.5-W lamp at tached to the middle of the back w al lof th e chamber; four boxes had a 6-W lamp attachedto the outside of the roof of the lever box. A noise gen-erator could be used to deliver w hite noise of about 80dB (re 20 pN/m2; General Radio Sound Level Meter,Model 1565-D, A scale) above background level througha 4-in. (10.2-cm) speaker mou nted inside each cham ber.In Boxes 7-10, electric shock could be delivered to thegrid floor through an auto transformer , a power t rans-former, an d d 150-kfl resistor in series wi th th e animal.In each insulat ion-board cham ber , there was a fan forventilation. A time-shared PDP-12 com puter controlledth e experimental equipm ent and recorded th e responses.Procedure

Pretraining. Each rat received at least two sessionsof continuous reinforcement train ing. Du ring these ses-


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228 W A R R E N H. M E C K AND RUSSELL M. CHURCHsions a pellet of food w as del ivered each minu te for 30m i n , and , in addition, each lever press produced food.The sess ion began w ith the inser t ion of the left lever,an d 10 responses were reinforced, af ter w hich th e leftlever w as retracted and the r ight lever inserted. T enright lever responses w ere then reinforced, followed byretraction of the r ight lever and inser t ion of the leftlever. This a l te rna t ion be tw een levers cont inued unt i lthe ra t had pressed each lever 30 t imes or 30 min hadpassed , w hichever came f ir s t . The housel igh t i l lumina te dthe cham ber a t a l l t imes dur in g the ses s ion.Training (Days 1-21 j. Half of the rats w ere t r a i nedto press the left lever (short response) follow ing a l ightt e rmina t ion s ignal of 2-sec duration and to press ther ight lever (long response) follow ing a l ight term inationsignal of 8-sec du ra t ion ; the r ema in ing ha l f of the ratswere tra ined in the same manner with sound onset asthe s ignal . On each tr ia l one of the tw o s ignal du rationswas randomly presented w i t h a probability of .5. Thehouseligh t w ent off (or the sound wen t on) for the se-lected duration; at the end of this period of time, thehouse l ight w as tu rned back on (or the sound w as t u rnedoff), and both levers were inserted into the box. If thea n i m a l made the correct response, a pellet of food w asimmediately delivered; if it made the incorrect response,no pellet w as delivered. W hen either lever w as pressed,there was a .5-sec delay and then both levers were re-tracted. Af te r an in ter t r ia l in terva l of 5 sec plus a geo-metrically distributed dura t ion w i th a m i n i m u m of .1sec and a mean of 40 sec, another tr ia l was begun. OnDays 1-5, if an incorrect response had been made onthe prev ious t r ia l, the same s t imulus dura t ion w as pre-sented again on the next trial (correction procedure).From Day 6 unt i l the end of the exper im ent , there w ereno correction trials. A daily session began w ithin 30 minof th e same t ime each day and las ted for 1 hr 50 min .A record was kept of the number of left and right re-sponses follow ing each of the two s ignals .Cross-modal training (Days 22-28), Each group ofra ts (l ight and sound) w as evenly divided into nonre-versal and reversal groups in terms of their originallyt ra ined response rules . The first 20 t r ia ls of the first dayof cross-modal training consisted of the same procedureused on Days 6-21. No dat a w ere collected on thesetrials. Thereafter, rats were retrained w i t h 2-sec and 8-sec s ignals from a new m odali ty (light or sound) . Ha l fof the rats were tested wi th the same response rule (re-inforcement of a left response follow ing a 2-sec s ignaland reinforcement of a right response follow ing an 8-secs ignal) , and ha l f w ere tested w i t h a reversed responserule (reinforcement of a right response follow ing an 8-sec s ignal and re inforcement Of a left response follow inga 2-sec signal).Signal-omission training (Days 29-35). The pro-cedure was the same as that used in cross-modal trainingexcept the s ignal was omitted.Retraining (Days 36-42). The rats received fur thersignal t r a in ing for 7 days u nder the same condi t ions a scross-modal training. Then there were 3 test days.Tests (Days 43-45). These 3 days are referred to asTest Days 1, 2, and 3. On Test Day 1, half of the ratshad l ight s ignal tra ining during the firs t 1.5 hr and soundsignal trials during the last 1.5 hr of a 3-hr session. Theremain ing half of the rats had the order of l ight andsound signal training reversed. The response rule for

both modali t ies remained the s ame as during cross-moda l t ra in ing. Test Day 2 was identical to Test Day1 except all response rules w ere reversed. Thus , theoriginal nonreversal groups received their first reversalcondi t ion, and the original reversal groups received theirsecond reversal condition. (Table 1 presents the condi-t ions of re inforcement for each group in each phase ofthe exper iment th rough Test Day 2.) Test Day 3 wasidentical to the first 7 days of retraining except (a) onlyeight subjects were tes ted, (b) s igna ls w ere e ither a 2-or an 8-sec duration of cons t an t .15-mA electric foot-shock (ra ther tha n l igh t or sound) , and (c) the responserules w ere reversed from those used in re t ra in ing fo rha lf of the rats in each original modali ty group.

ResultsThe p erformances of the n onreversal andreversal l ight groups w ere s imilar throu gh-ou t training (see Table 1). During the lastseven sessions of t ra ining, the m e an per-centage of correct responses of ra ts in thenonreversal group trained w ith light w as notsignificantly different from the mean per-centage correct of ra ts in the reversal grou ptrained w i th l ight. The performances of thenonreversal and reversal groups tra ine d w i t hsound were also similar. The percentage of

correct responses of ra ts in the groupst ra ined w i t h sound, however , w as signifi-cantly higher than the percentage of correctresponses of ra ts in the groups tra ined w i thlight, r(18) = 4.35, p


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ABSTRACTION OF TEMPORAL ATTRIBUTES 229wi th sound) had a mean percentage correctnot significantly less than 50%, t(4) = 1.5,p < .10, but signif icant ly different from thecomparable nonreversal group, f(8) = = 3.0,p < .05.Figure 1 show s the percentage correct forindividual subjects in each group averagedover responses to both 2-sec and 8-sec du-rations for the first session of cross-modaltraining.Figure 2 shows that the difference be-tween nonreversal and reversal groups w asmain ta ined for at least five sessions of re-t ra in ing, fs(8) > 2,36, ps < .05. The reversal-nonreversal differences for the seven sessionsof cross-m odal t ra ining w ere greater for ra tst ransferred to sound tha n for ra ts t rans ferredto light. An analysis of variance of the per-centage of correct response during cross-modal t ra inin g, w i th factors reversal-non-reversal, signal (light or sound) , and session,

showed all three main effects to be reliable:reversal-nonreversal, F(l, 120) = 77.0, p


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230 W A R R E N H . M E C K A N D RUSSELL M . CHURCH

SOUND

G R O U PFigure 1. Percentage correct fo r ind ividual subjects dur-ing the first session of cross-modal test ing fo r subjectsw i t h nonreversal and reversal classification rules. (Fig-ures were draw n w i th a comp uter program developedby Hayes, 1981.)

accuracy to long signals of r a t s t r an s -ferred to light w as rel iably greater than fo rrats t ransfer red to sound , f ( 18 ) = 3.72,p 3.77, p < .02.In addi t ion, performance to sound signalsw as bet ter than performance to l ight signals,*(9) = 4,1, /x.OOl. T he reversal groupsalso had a percentage of correct responsesfor the retrained signal modality that w assignificantly greater than chance ts(4) ^.3.78, p < .02.The m ajor resul t w as t h a t theperformance of the reversal groups on theoriginal ly t ra ined signal modali ty was no tsignificantly different from chance fo r eitherlight or sound, f s (4) < 1.

The resul ts from Test Day 2 are given inthe last column of Table 1. All original non-reversal groups had levels of performancebelow chance for both l ight and sound,t s ( 9 ) ;> 2.41, p < .05. The original reversalgroups also had a level of perform an ce belowchance for the retrained signal modali ty ,?(9) = 2.87, p < .02. In contrast , perfor-mance on the original ly t ra ined signal mo-dality w as significantly above chance,t(9) = 2.93, p < .02.With the exception of an initia l period inwhich no responding occurred, the resultsw i th electric shock as a s igna l (Test D ay 3 )w ere similar to those for previous cross-modal t ra ining. Combining over ra ts origi-nally t ra ine d w ith l ight or sound signals , thenonreversal groups w ere 64% 3% correct ,a level of performance signif icant ly abovechance, r(3) = 6.37, p < .01; the reversalgroups w ere 36% 2% correct, a level ofperformance significantly below chance,f ( 3 ) = 11.2, p < .01.

DiscussionThe major finding of Exper imen t 1 wa sthe posi t ive and negat ive cross-modal t rans-fer of a specific dura t ion d i sc r imina t ion . Thisresult replicates previous reports from ourlaboratory (Meek & Church, in press;Rob-

N O N R E V E R S A L S O U N DL IGHT0---0- S O U N DA - - - A L I G H T

DAYFigure 2. Percentage correct as a function of d ay s ofcross-modal t ran sfer tes t ing fo r groups w i th nonreversaland reversal classification rules. (Thes t imu lu s u sed inthe cross-modal t ransfer test [sound or l igh t ] is listedin the legend.)


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ABSTRACTIO N OF T E M P O R A L A T T R IB U T E S 231erts, 1982). Both positive and negative trans-fer of dura t ion were demons t ra ted dur ingthe first session of cross-modal t ra inin g, andthe difference betw een nonreversa l and re-versal groups persisted for five sessions.The rela t ively long random inter tr ia l in^terval eliminated the possibili ty that the in-ter t r ia l in terval mediated the t ransfer effectsince no control by t ime w as observed w h e nthe signal w as omit ted. The a m oun t of t r a n s -fer w as greater, and the t ran sfer las tedlonger than the cross-modal t ransfer by an-imals previously reported (e.g., Over &Mackintosh, 1969). The fact that the posi-tive t rans fer w as somew hat grea ter than thenegative t ran sfer probably reflects some newlearning tha t occurred dur ing the first ses-sion.The resul ts w i th sound and l ight s ignalsdiffered in three w a y s : (a) The asymptotict empora l discrimina t ion w i th sound w as sig-nificantly greater than the asymptotic tem-poral discr im ina t ion w i th l ight d ur ing bothtraining and retraining, (b) transfer fromlight to sound w as grea ter than from soundto light, and (c) rats transferred to light, butnot those to sound, made more erroneousshort responses than long responses. Similardifferences between l ight and sound s igna ldurat ions have been obta ined w i th hum ansubjects (e.g., Goldstone & Goldfarb, 1966).Posner (1978) , in descr ibing human in -formation processing, proposed that undersome condit ions audi tory signals wi l l haveautomatic access to in format ion ana lyzersand visua l signals wi l l not . If automaticitycontributes to a high level of performance,the asymptot ic level of performance mightgenerally be higher fo r soun d than l ight . Ofcourse, the in tensi ty of s t imulus change isalso a relevant variable. According to Pos-ner's proposal, to initiate visual processing,subjects must learn to direct attention to thevisual s t imu lus ; no such learn ing is requiredfor auditory processing. Thus subjects trans-ferred from light to sound wou ld havegreater t ransfer than subjects transferredfrom sound to light. Finally, according toPosner's proposal, the t ime to process a vi-sual s ignal is longer and more variable thanthe t ime to process an auditory signal. If thiswere the case in the ra ts t ra ined w ith soundsignals and transferred to light signals, the

l ight would be slower to initiate the t imingprocess. T his w ould produce a shorter sub-ject ive t ime, w hich results in the observeda symmet r i ca l error rates for the sound-lightgroup, i .e. , more short than long errors.Other w ork (Meek, Note 1) has used dif-ferent tests to demons t ra te tha t there arefundamen ta l differences in the tem poral pro-cessing of l ight and sound signals by rats.The resul ts of Tes t Days 1 and 2 for thenonreversal groups are simply replicat ions.On Test D ay 1, the ra ts cont inued to performthe t rained responses; on Test Day 2, theyhad nega tive t ransfer w hen the response ru lew as reversed. The im portan t resul ts from thetest days w ere obta ined from the originalreversal groups. Du ring Test Days 1 and 2 ,these groups differentially responded to lightand sound signals , a l though the same rein-forcement contingency applied to both sig-nals . Perform ance could be predicted by thesignal modality and response rule originallytrained. Such p erform an ce indicates tha tsensory-specific m em ories w ere establishedby the original t ra ining condit ions and con-tinued to persist even follow ing cross-modalt ransfer . This suggests that sensory-specif icinform ation is m aintained in conjunctionw i th an at t r ibute abstract ion system. Ani-mal s may ut i lize th i s in format ion netw orkby m atch ing sens ory-specific and nonspecificassociations w i t h the s t im uli curren t ly avai l-able. This finding is consonan t w i th w ork inh u m a n cognit ion w herein people can recallsensory-specific information al though theemphasis of the t a sk is on abs t rac t ing infor-m ation that is equivalen t betw een modali ties(e.g., Broadbent, 1958; Posner, 1978).The results from Test D a y 3 w ith electricshock provided another example of cross-m odal t rans fer . The m ain purpose of th is testw as to determ ine w hether ra t s th a t exper i-enced negative transfer (rats in the reversalgroups) learned not to t r ans fe r a responserule to a new modality. The result was thatthe an imals con t inued to use the responserule last trained w hen t ransferred to the newelectric shock signal.In summ ary , the major finding from thisexperiment w as cross-modal t ransfer of aspecific duration discrimination. In addition,(a ) d i sc r imina t ion performance w as bet terfor sound than fo r light signals, (b ) t ransfer


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232 WARREN H . MECK A ND RUSSELL M . CHURCHfrom l igh t to sound w as greater t h a n fromsound to l ight, and (c) a l though the a t t r ibu teof dura t ion may be used independently ofstimulus modali ty, modali ty-specific infor-mat ion i s al so ava i lable for use.

Experiment 2: Temporal Generalization(Trans fe r of Dura t ion)To demons t r a t e the general i ty of cross-m odal t r ans fe r of dura t ion , w e a t tempted toreplicate the posi t ive transfer resul ts of theprevious experimen t w i th a different t imingprocedure , a temporal general izat ion task.In thi s procedure only one lever w as us ed,

and except fo r ear ly stages of t r a in ing, itremained in the box. Ra ts w ere g iven t r a in -in g w i th th r ee du r a t ion s of a l ight signal.Half of the rats received signals of 2, 4, or6 sec, and half received signals of 6, 12 , or18 sec. If the s ignal was t h e in te rmedia teone, w hich occurred on a random half of thet r ia l s , re inforcement was pr im ed af te r a r an -dom in terval . I f the s ignal w as either of theextreme durations , there was no reinforce-me n t . The me a s u r e was the response ratedu r ing the f i rs t 5 sec af te r s igna l te rmina-tion. A similar procedure has been used ex-tensively in our laboratory (e.g., Church &Gibbon , 1982), arid it leads to s low tempora ldiscrimination learning. This procedure dif-fers from the one used in Exper imen t 1 inseveral respects. In the choice discr im inationprocedure, the an imal reports which of tworemem bered s igna l dura t ions is closer to thepresented s ignal by ma k i n g one of two dis-crete responses; in the temporal general iza-tion procedure, the an im al report s w he therthe remembered s ignal durat ion is closeenough to the presented s ignal by va ry ingits re sponse ra te .

MethodSubjects and Apparatus

T w e n t y ra ts , s imi lar to those used in Exper iment 1,w e r e used in th i s exper iment . The appara tus describedin Exper imen t 1 w a s used.Procedure

Pretraining. Each rat received at least two sessionsof cont inuous reinforcement t ra in ing. D uring these ses-s ions a pellet of food w as del ivered each minute for 30m in , and , in addition, each lever press produced food.Only the left lever was used. The session ended w h en

the rat had received 60 reinforcements or 30 min hadpassed, w hichever came first. For the next 2 days , ra tswere given discrete tr ials of a signal presentation(houselight off) followed immedia te l y by lever insertionand a random-interval schedule of reinforcement w itha 3-sec l imited hold. Reinforcem ent in terva ls w ere 1 secplus a geometr ica lly dis t ributed d ura t ion w i th a m i n i -m um of. 1 sec and a m ean of 5 sec. T he lever retractedfollow ing the reinforced response. The reinforced signaldura t ion w a s 4 s ec fo r half of the rats (4-sec group) and12 sec for the others (12-sec group). Intertrial in tervalsw ere 10 sec plus a geometr ica lly dis t r ibuted dura t ionw i t h a m i n i m u m of . 1 sec and a mean of 30 sec. Therats w ere tested in tw o sessions of 10 rats each. Theyw e r e random ly ass igned; 5 in each session w ere fromthe 4-sec group and 5 from the 12-sec group. Sessionsbegan w i thin 30 min of the sam e t ime each day andlasted 1 hr'50 m i n .

Training with unreinforced signal durations (Days1-40). Train ing w as the same as the f ina l condit ion ofpre t r a i n ing except tha t unreinforced s ignal dura t ions of2 and 6 sec for the 4-sec group and 6 and 18 sec for the12-sec group were also presented. The reinforced du-ra t ion w as presen ted on a random half of the t r ia ls , andt h e t w o unreinforced dura t ions w ere randomly presentedw i t h equal probabi l i ty on the rem ain in g t r ial s . The re-sponse lever w as w i t h d r a w n fol lowing nonreinforced sig-na l tr ials according to the rule used for reinforced signaltrials except that no reinforcement w as g iven . Beginningon Day 6 of training, the response lever was present ata ll t imes during the session.Cross-modal training (Day 41). Rats t ra ined w i t ha light-oft* signal w ere tested w i t h a sound-on signal.Except for the change in modali ty , the procedure re-m ained the s a m e as dur in g or igina l t ra in ing .Data taken. Responses w ere recorded as a functionof time for the first 5 sec of the random-interval rein-forcement schedule. A mean response rate was calcu-lated for these 5-sec intervals.

ResultsFigure 3 (left pane l ) show s m ean response

rate (responses/min) fo r subjects in the 4-sec group dur ing the las t 5 day s of t r a in ing(l ight s ignal) and the single test day (soundsignal) at each s ignal dura t ion. The responserate follow ing the re inforced s ignal (/?) andthe mean of the response rates follow ing thetw o unreinforced s ignals (/) w ere combinedin a discr imination index, ( J R . U)/R. Adiscrimination index of 0 w ould reflect chanceperform ance; h igher values w ould reflectbet ter d iscr imination. During the last 5 d a y sof training, the mean discrimination ratio forsubjects in the 4-sec grou p was .23% .03%;dur ing the 1 day of cross-m odal training, thi sdiscrimination index for the nine subjectsthat responded was also .23% .03%, anunrel iable difference be tween t r a in ing andtesting.


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ABSTRACTION OF TEMPORAL ATTRIBUTES j 233Figure 3 (right panel) shqws mean re-sponse rate for rats in the 12-sec group dur-in g the last 5 days of training (light signal)an d the single test day (sound signal) at eachsignal duration. During the last 5 days oft raining, the mean discr imination index fo rsubjects in the 12-sec group 'was .21% .04%. D urin g the 1 day of cross-modal t rain-ing, this discrimination index for the sevensubjects tha t responded w as .23% .03%, anunreliable difference between t ra ining andtesting.Dur ing training, the discrimination mea-sure for both 4-sec and 12-sec groups w as

reliably greater than chance, ts(9) s = 7,0,ps < .05, but the difference betw een thesetw o groups w as n ot s ignif icant , f ( 1 8 ) < l .During cross-modal training, the accuracyof subjects that responded in all groups w asreliably greater than chance, *s(15) a 2.36,ps < .05, and there were no reliable differ-ences in accuracy between training and test-ing, ?s(15) < 1. However , the response rateof both groups w as low er du ring cross-m odaltraining tha n du ring original training, f(6) =2.64, p < .05 and f(8) = 2.33, p < .05.

DiscussionDuring tes ting w i th the new modali ty ,there w as a reduction in response rate, but

the maximum remained a t the reinforcedvalue w ith no change in the accuracy of thediscrimination. The reduction in responserate shows that there w as some influence ofmodali ty , but the forpi of the generalizationfunctions indicates that ra ts that learned atemporal criterion (4 or 12 sec) wh e n theinternal clock w as driven by a l ight signalused th e same cri terion w hen th e clock w asdriven by a noise signal. F or this temporalgeneralization task , as for the previous task,any stimulus change (e.g., light or sound)w as sufficient to s tar t an intern al clock, andthe duration registered by the clock w as amajor de te rminan t of performance.Experiment 3:Condi tional D iscrim inations (Transferof Duration and Temporal Location)

In the previous tw o experiments , the an-imals had only to form a simple associationbetween a duration and a response. In Ex-periment 1, a "long" response w as ass ociatedwi th s ignal durations greater tha n some cri-terion; in Experiment 2, rapid response rateswere associated wi t h signal durations closeenough to some cr i te r ion/These s imple as-sociations between signal durations and re-sponses transferred from one modal i ty toanother (e.g., vision to audition).

80

5 6 UJ

- TRAIN (LIGHT)o-----O TEST (SOUND)

60

20

1 2 - 1 8T IM E ( S E C )

Figure 3. Average number of responses per minute as a function of s ignal duration under conditions oforiginal tra ining and cross-modal tes t ing. (Left panel shows data for the group trained w ith responsesreinforced after 4-sec signals; the right panel shows data for the group trained w ith responses reinforcedaf ter 12-sec signals.)


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234 W A R R E N H. MECK AND RUSSELL M. CHURCHTable 2Signal Duration, Reinforced Response, andReinforcement Rule

Signaldurat ion(in sec):A B c

Rein-forcedre - Rulesponse \A-C\ + 1 B

Larger(A/C)or(CIA)Same-different t raining (Days 1-50 and 61-65)

123123

24542535262

XXXXXX

22222222222

111333

New24524352526

LRRL

subset t r a in ing.

123321

XXXXXX

\2331.51

( D a y s 51-60)11133334455

Cross-modality t r a i n ing ( D ay s123123

1X33X1

111333

LRRL

123321

2222222 ,2222

66-75)1X33X1

111221.671.672.52.533

12331.51

Note. X = 1 , 2, or 3 sec.

Previous research wi th human subjectshas typically obtained cross-modal transferin task s involving the processing of simpleunid imens ional discriminations bu t modal-ity-specific learning in tasks involving com-plex pattern information processing (e.g.,Freides, 1974), In the present experiment ,the an imal s had a much more difficult t askthan in the firs t tw o experiments. A sequenceof three s ignals of var ious durat ions w as pre-sented. The animals had to select w hich ele-m e n t s of the sequence to t ime, and then touse a conditional classification rule. Thequestion w as whether , rats would transfer acomplex classification rule involving severalsequent ial ly presented durat ions from onemodali ty to another.

MethodSubjects and Apparatus

Tw enty rats s imilar to those used in Experiment 1were used in this experiment. The apparatus describedin Experiment 1 was used.Procedure

Pretraining. The pre t raining described in Experi-men t 1 was used.Same-different training (Days 1-50). Half of therats w ere trained on a sam e-different condit ional dis-crimination. Signals consisted of three segments wi thdurat ions , A, B, and C. A w hite noise signal w as on fordurat ion A, off for durat ion B , and on again for durat ionC. The durat ions A, B, and C could be 1, 2, or 3 sec,making a total of 27 possible signal combinations. Forthis experiment , only 18 of the 27 possible cases w ereused; those signals having segment C = 2 were omit ted(see Table 2.) On each t rial a signal combinat ion w aspresented. Then both levers were inserted into th e box.If the rat pressed the correct lever, food w as delivered;w h e n either lever w as pressed, there w a s a .5-sec delayand then both levers were retracted. After a 30-sec in -tertrial interval, another t ria l w as begun. Signals w ererandom ly presented w ith equal probabili ty. The house-light w as on a t a l l t imes during the session w hich beganwi th in 30 m in of the sa me t im e each day and lasted for1 hr 50 min . A record w as kept of the number of leftan d right responses following each signal.In the same-different condit ional discriminat ion, theleft (same) response was reinforced if \AC\ - 0 sec,an d the right (different) response was reinforced if\A-C\ = 1 sec. Intermediate values, in w h ic h \AC\ =1, were not reinforced. (Table 2. s ta tes th e experi-menter's classif icat ion rule w i t h the addition of a con-s tan t , 1, to constrain th e variable between 1 and 3 sec.)Dur ing the t ra in in g phase, a left response w as reinforcedif A and C w ere both 1 or 3 sec; a right response w asreinforced if A = 3 and C = 1 or if A = 1 and C = 3.The durat ion of B w as irrelevant . If the rat made theincorrect response, no pellet w as delivered, and the samesignal w as presented again on the next t rial (correct ionmethod).Testing on a new subset of signals (Days 51-60).The procedure w as s imilar to that previously describedexcept that a new subse t of 11 unreinforced signals w asadded, w ith durat ion B = 2 sec. From D ay 51 to theen d of the experiment , there were no correct ion trials.Table 2 shows the signal presentat ions and experi-menter's classif icat ion rules used for this stage of test ing.Retraining (Days 61-65). Training w as the same ason Days 1 -50 except tha t no correct ion trials w ere given.Oddity training (Days 1-65). Half of the ra ts w e retrained on an oddity condit ional discriminat ion. Thet r a in ing procedure wa s similar to that of the same-dif-ferent discriminat ion except as described below.In the oddity condit ional discriminat ion, the segmentclassification rules were such that if A = B, classify C;ifA = C, classify B; if B = C, classify A. If the segmentto be classified ( the odd segm ent) w as 1 sec, the leftresponse (sh ort) w as reinforced; if the segment w as 3sec, the right response (long) w as reinforced. Interme-diate values, in w h i c h the odd segment equaled 2 sec,


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ABSTRACTION OF T E M P O R A L ATTRIBUTES 235were not reinforced. The durations of A, B, or C couldbe relevant. If the rat made the incorrect response, nopellet was delivered, and the same signal was presentedagain on the next tr ial (correction method). From Day51 to the end of the experiment, there were nocorrectiontr ials .Cross-modality training with a new modality (Days66-75). Five subjects from each of the two groups(same-different and oddity) continued and were iden-tically treated in this phase of the experiment. Therew ere tw o major changes from previous training: (a) T hemodali ty of the signal w as changed from sound onsetto light te rmina t ion , and (b) there w ere tw o classifi-cation ru le s tha t w ou ld w ork . T he rats could use thepreviously described same-different rule based on a com-parison of the duration of A and C, or, more simply,they could use the duration of B. If B = 1 sec, a leftresponse rule was reinforced; if B = 3 sec, a right re-sponse w as reinforced. Intermediate values, in whichB = 2 sec, were not reinforced for either response. Table2 shows the signals and the experim enter ' s classificationrules used for cross-modal training.

ResultsSame-Different Training

The same-different discr iminat ionw a s n oteasy to learn. A fter 50 sessions, only 3 of the10 rats learned the t ask . The results fromthese 3 subjects for the last 5 days of re-training are shown in the left panel ofFigure 4.A s ingle factor (w ithin-subjects) analys isof variance indicated a significant relationbetw een the percentages of right (different)responses as a function of the absolute dif-ference between A and C, F(2, 4) = 49, p

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226-243 Abstraction of Temporal Attributes