Vol. 49 No. 4 November 1996 Section 4 Page 357

T HE QUA RTE RLY JO U R NA L OF EX P ER IM E N TA L PSYCH OL OG Y, 1996, 49B (4), 357± 381

Com bining O perant-baselin e-derived C ond itio ned E xcitors and Inh ib itors from th e Sam e and Different Incentive Classes: An Investigatio n of A ppetitive± Aversive In teraction s Stanley J. Weiss, D avid A . Thom as, and R ichard D. Weissm an The A merica n U niversity, Wa shington, DC, U.S.A.

T h e dy n am ics of ap p etitive± aversive interaction th eory w ere assay ed in an exp erim en t w h ere excitors an d inh ibitor s fro m th e sam e an d differen t incen tive classes w ere com p ou nd ed . E xcitatory and inh ibitory ince ntive p ro per ties acqu ired by th e d iscrim inative stim u li resu lted fro m th e reinforcem en t d ifferences betw een com p on ents of four- com p o n ent m ultiple train ing sch edu les, w ith th e in¯ u en ce of com p eting p erip her al res po nse s factore d into th e d esign . Rats’ bar p ressin g w as m aintained in to ne an d in click by food or free-o p er ant sh ock avoidan ce; extinction w as p ro g ram m ed in click-p lus-light and in th e sim ultan eous absen ce of ton e, click, and ligh t. In Test 1, an excitor th at occasio n ed op era nt respo n din g and an inhibitor th at occasio ned resp on se cessatio n w ere com p ou nd ed . H ere, com po u n d ing an inhibitor w ith an excitor fro m th e sam e incen tive class redu ced re sp on d ing sign i® can tly m ore th an d id com po u n d ing an inh ibitor w ith an excitor fro m th e oth er incen tive class. In Test 2, the com po u n d s con sisted of ele m ents th at ind ividu ally occasion ed op eran t resp on d ing. H ere, com po u n d ing s tim uli th at w ere excitors fro m d ifferen t incen tive classes ap p eared to create re cipro cal inh ibition th at cou n te racted th e add itive effects p ro d u ced w h en th ese stim u li w ere excitors fr om th e s am e incen tive class. Pred iction s fr om app etitive± aver sive interactio n th eory an d Weiss’ two -factor m od el of stimu lus con trol w ere co n ® r m ed w ithin th is exp erim en tal design , w h ere all con d ition ing w as a by-pro d u ct of the behav iou ral con tingen cies p ro gr am m ed o n the op er an t baselines.

T here are a num ber of general th eories of m otivated behaviour th at postulate two central processes or system sÐ the ap petitive, b ased o n reactions to stimuli that attract the org an ism , an d the aversiv e, based o n reactions to stimuli th at repel it (G ray, 1975; K on orski, 1967 ; M ow rer, 1960). A ccording to ap petitive± aversive interaction theory (D ickinso n &

Requ ests for reprin ts shou ld be sen t to Stan ley J. Weiss, D epartm ent of Psych ology, The Am erican U niversi ty, Wash ingto n, D C 20815, U.S.A. This researc h was sup porte d in part by G ran t M H -16853 from the Nationa l Institute of M ental H ealth , U nited States Public He alth Service , aw arde d to the ® rst author. It was presen ted at the Psycho nom ic S oc iety Conven tio n, Wash in gto n, DC , 19 93. q

1996 The E xp erim ental Psych olog y S ociety

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W E IS S , T H O M A S , W E IS S M A N

Pearce, 1977), w hen behaviour is m aintained by o ne class of reinforcer, (1) the behaviour sh ou ld b e energiz ed by presenting a condition ed excitor for that system (e.g. B ull & O ver m ier, 196 8; E m urian & Weiss, 1972; Rescorla & L oL ordo, 1965; Weiss, 1971, 1976 , 1977, 1978; Weiss & Schindler, 1985, E xp. 2, 1989; Weism an & L itner, 1969) or a conditioned inhibitor for th e oth er system (e.g. G rossen, K ostansek, & B olles, 1969), an d (2) th e behaviour should be red uced by presen ting a conditioned inhib itor for that system (e.g. Reberg & Black, 1969; Rescorla & L oL ord o, 1965; Szw ejkow ska & K on orski, 1959 ; Weiss & S chind ler, 1985, E xp. 1; Weism an & L itner, 1969) or a conditioned excitor for the other m otivational system (e.g. Brad y, 1951; Bu ll, 1970; D avis, 1968 ; D avis & K reuter, 1972 ; E stes & Skinner, 1941; G rossen, et al., 1969; O ver m ier, B ull, & Pack, 1971; Weiss & Schindler, 19 89). Som e contrad ictory evidence to the reciprocally inhibiting interactions cited above has been reported (Bacon & B indra, 1967; C oulso n & Walsh, 1968; D avis & K reuter, 1972; D eVito & Fo w ler, 1982; H enton , 1972; O ver m ier & Bull, 1970; O ver m ier & Payne, 1971; O ver m ier & Schw arzkopf, 1974). H ow ever, it should be ap preciated that such contradictions m ay well, at least in part, be due to the fact that ``. . . the outcom e of these su m m ation tests d epends to a large extent o n the interaction between the m o tor patter ns established d uring ap petitive an d aversive training rather th an [just] the effect of the C S on som e central resp onse or m otivational system ’ ’ (D ickinso n, 1977, p. 72; see also Weiss, 1978 ). Id entifying these p erip heral co ntributions to the outcom e of these behav ioural assays is often dif® cult. N evertheless, w hen Weiss an d S chind ler (1989) did so in the stu dy repor ted by O verm ier an d Schw arzkopf (1974)Ð results th at ap parently contradicted ap petitive± aversive interaction theory becam e entirely co nsisten t w ith the theory. In the design of the p resent experiment, the co ntribution of com peting or com plim entary op eran ts (see D ickinson, 1977; Trap old & O ver m ier, 1972) w as directly factored into the test outcom es, p er m itting the in¯ uence of th e incentive m an ip ulation to be revealed unam biguously. First of all, excitors alw ays occasion ed barpressing, an d inhibitors never occasio ned barpressing, irrespective of their reinforcem ent class. Second, all tests w ere co nducted in extinction to avoid the presentation of stimuliÐ such as food, sh ock, or feeder clicksÐ that m ight elicit peripheral responses that could com pete w ith the d ependent variable: bar p ressing. T he scienti® c pow er an d parsimony of ap petitive± aversiv e inter action theory is derived from the assum ption that the b ehaving organ ism evalu ates different re inforcem ent conditions as an affective com parator. A ccording to this for m ulation, affectively com parable stimuli are m otivationally equivalent irrespective of w heth er these affective states are derived from the ap petitive or the aversiv e system s (D ickin so n & D earing, 1979; D ickinson & Pearce, 1977; M illenson & de V illiers, 1972; Rescorla & Solom o n, 1967). T his is n ot m ean t to imply th at an an imal does n ot distinguish between shock an d the absence of food or between food an d safety from shock. Rather, ap petitive± aversive interaction theory em p hasiz es that the com m o n affective state derived from these differen t repelling or attractive circum stances can have com parable effects in m otivating behavio ur. T hus, th is is fundam entally a m odel b ased on hedonics. Predictions from the principle of affective com parab ility w ere substantiated w hen: (1) aversively co ntrolled behaviour w as energiz ed by a signal for an aversive (repelling) event, w hether that even t w as the presentation of shock (aversive excitor) (Rescorla &

E X C IT O R S A N D IN H IB IT O R S

359

L oL ordo, 1965; Weism an & L itner, 1969) or the rem oval of food (ap petitive inhibitor) (G rossen et al., 1969); (2) an ap petitive inh ib itor blocked a shock-derived associatio n co m parably to a shock-associated aversive excitor (D ickinson & D earing, 1979); (3) an ap petitive excitor accelerated (superconditioned) con ditioned suppression to an add ed elem ent as an aversive inhibitor would (D ickinson, 19 77); (4) an ap petitive inhibitor an d aversive excitor b oth served as conditioned punish ers (L eitenberg, 1965); an d (5) a stimulus associated w ith food (an ap petitive excitor) as w ell as one associated w ith safety from shock (an aversive inhib itor) served as condition ed reinforcers (L oL ord o, 1969). T he goal of the cur rent research w as to assay the dynam ics of ap petitive± aversive interaction theory through stimulus com pounding tests in an experiment in w hich all co nditioning w as a product of the free-o peran t behaviou ral co ntingencies program m ed o n the training b aselines. T h at is, excitatory an d in hibitory properties of the discrim inative stimuli resulted from th e rein forcem ent d ifferences b etween com ponents of the m ultiple train ing schedules. (In contrast, in the tran sfer-of-co ntrol parad igm the C S acquires its incentive properties in an independent classical cond ition ing phase.) To this end, fourco m ponent tr aining b aselines were developed that created the ap petitive an d aversive ex citors an d inhibitors necessary to com pare the effects of com pounding (1) an excitor of on e incentive class w ith an excitor of the (a) sam e or (b) opposing incentive class, an d (2) an ex citor of one incentive class w ith an inhibitor of the (a) sam e or (b) opposing incentive class. O nly o ne study (G rossen et al., 1969) has directly supported, through a stimulus co m pounding test, p redictions of ap p etitive± aversive inte raction theory for situations co m parable to 2b, ab ove. F urther exploration of the behaviour resulting from that con® guration of excitors an d inh ib itors from opposing incentive classes w as a m ajor objective of this study. C o n® gurations of excitors an d inhibitors described by 1 a, 1b, an d 2a, above, were included as system atic replication s of these well-established predictions of ap p etitive± aversion interaction theory an d to assay the integ rity of our m an ipu lations.

D esig n o f Ex perim en t A schem atic representation of the training received by the four g roups in this experim ent is show n in the upper p an el of Table 1. T he two intraincentive g roupsÐ ap p etitive (A) an d aversive (B )Ð are presented on the left. T here w as, in fact, functionally only one interincen tive group that earn ed food in one stimulus an d avo ided shock in an other. Two interincen tive g rou psÐ C an d D Ð w ere created through stimulu s-by-incentive cou nterbalan cing. Fo r both intraincentive g roups, barpressing w as m aintained in tone (T) an d in click D (C) discrim in ative stimuli (S s) by the sam e class of reinforcer, ap petitive (food) or aversive (shock avo idan ce). In the ab sence of T an d C (TC ), there w as no co ntingenc y oper ating (extinction ). Fo od w as ear ned on a variable-interval (V I) schedule. T h e aversive reinforcer w as the free-operan t avoidan ce (FO A ) of shock w herein each barpress postponed a b rief shock by 25 sec. T his training w as m ean t to establish b oth the T an d the C as ap p etitive excitors (Ap+ ) or aversive excitors (Av+ ). In com parison, for the interincentive g roup, barpressing w as m aintained in o ne stimulus (T or C ) by food an d in the other (C or T ) by FO A , m aking one of these stimuli an Ap+ an d the oth er an Av+ .

360

W E IS S , T H O M A S , W E IS S M A N TABLE 1 D es ig n o f E x p e rim e n t

Intra incentive Groups

Train ing

Tone

Click

C+ L

A.

App+ (VI)

App+ (V I)

App 2 (E X T)

B.

Av+ (FO A)

Av+ (FO A)

Av 2 (E X T)

I nterincentive Groups Tone

Click

C+ L

C.

App+ (V I)

Av+ (FOA )

Av 2 (E XT )

D.

Av+ (FOA )

App+ (V I)

App 2 (E XT )

Tone- plus-light Tes t 1: Com pou nding excitor s an d inhibito rs

Tone-plus-light

A.

App+

App 2

C.

App+

Av 2

B.

Av+

Av 2

D.

Av+

App 2

Tone-plus-click Tes t 2: Com pou nding excitor s

Tone-plus-click

A.

App+

App+

C.

App+

Av+

B.

Av+

Av+

D.

Av+

App+

N ote: VI = v ariable -interval schedule; F OA = free-op eran t avoid an ce; EX T = no con tin gen cy ope rating; + = con dition ed excitor ; 2 = con dition ed inhibitor ; C + L = click an d ligh t presented simultan eou sly; App = ap petitive; Av = aver sive. A, B, C, and D indicate th e four train ing grou ps.

Fo r all g rou ps, light (L ) w as m ad e a conditioned inh ibitor through the A + /A B 2 discrim inatio n parad igm . T he contingency prog ram m ed in C w as discontinued (i.e. ex tinction w as instituted) w hen L w as presented simultaneously w ith C (C L ). T his m ad e L an ap petitive inhibitor (Ap 2 ) w hen food w as program m ed in C , an d an aversive inhibitor (Av 2 ) w h en F O A w as pro gram m ed in C . T his training produ ces an extrem ely pow erful inhibitor becau se the inh ibitor is created w ithin a potent excitatory co ntext (Rescorla, 1969; Rescorla & Wag ner, 1972; Wag ner & Rescorla, 1972). A fter the rats had b een b rought u nd er stimu lus control on the four-com ponent training baselines described above, they received two stimulus-com pounding tests. T hese tests have proved valuable in revealing the con tribution of the cond ition ed incentive-m otive m echan ism , as well as that of the discrim inative response process, to stimulus con trol. Weiss’ (1978) two-factor m odel of stimulus co ntrol w as ap plied in pred icting the resu lts of the stimulus-com pounding tests ad m inistered in the present experiment. T he m odel assum es th at the resp onse discriminative an d incentive p roperties acquired in training D by each of the S s com pounded com b ine algebraically to prod uce a resultant behaviour. T he m odel has been successful in system atizing the results of the m ore than 100 stimulu sco m pounding an d stimulu s-gen eralizatio n peak shift studies perform ed prior to, an d after, its publicatio n.


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Test 1: Compounding E xcitors with I nhibitors from the S a me a nd the Opposite I ncentive Cla ss. In Test 1 (m iddle p an el of Table 1) T, C , an d tone-plus-ligh t (T L ) w ere presented. Fo r the intraincentive groups, L w as an inhibitor from the sam e incentive class as the excitor (T ). Fo r th e interincentive g roups, L w as an inhibitor from the incentive class op posite to that of the excitor. O n the basis of the respo nse factor alo ne, for both in traincentive an d interincentive g roups, T L should control a rate w ithin the ran ge occasio ned by the presentation of T or L alone. T his is becau se resp onse reduction controlled by L w ould occasion peripheral oper an t(s) com p eting w ith the barpressing occasion ed by T for b oth groups. H owever, L w as an inhibitor of the excitor’s incentive class for the intraincentive g roups, cau sing it to lower respo nding further by reducing the m otive state exciting respond ing in T. In contrast, L w as an inhibitor of the incentive class o pposite to T ’ s excitor for the interincentive g roups. In this situation, accordin g to ap petitive± aversive interaction th eory, L w ould m otivatio nally au gm ent T ’ s excitation. T herefore, in Test 1 L should redu ce respo nding in T signi® can tly m ore for the intraincentive g roups than for the interincentive g roups. Test 2: C ompounding E xcitors with E xcitors of the S a me a nd Opposite I ncentive Cla ss. In Test 2 (bottom section of Table 1), T, C , an d to ne-plus-click (T C ) w ere prese nted. In T C , both intraincen tive an d interin centive g roups w ere in th e presence of two stimuli that occasio ned barpressing, w hereas in T or C they w ere in the presen ce of only o ne. T herefore, on the basis of the respo nse factor alone, m ore responding wo uld be predicted in T C than in T or C (add itive sum m ation). In addition, as T an d C were excitors from the sam e incentive class for the in traincentive g rou ps, ap petitive excitation should be g reater in TC th an in either elem en t, further enhan cing th e ad ditive sum m ation (see Weiss, 1971). In contrast, for the interincentive groups, T an d C w ere excitors from opposite incentive classes. H ere, according to ap petitive± aversive interaction theory, TC would produce recipro cal in hib ition that decreases the overall m otive state supporting barpressing. T h is should substantially reduce, or even eliminate, the ad ditive su m m atio n that the respon se process w ould sup port (see Weiss & Schindler, 1989).

M eth o d Subjects Twen ty m ale L on g-E vans h ood ed ra ts serv ed as su bjects. Training com m en ced after th ey h ad been d epriv ed to app rox im ately 80% of their ad libitum w eigh ts, w h ich ra ng ed fro m 349 to 430 g. T h ey w ere h ou se d in ind ividu al cages, w h ere w ater w as always available, in a r oom th at w as c on tinu ou sly illum inated by overh ead ¯ u orescen t lights. Food acqu ired du rin g a tra ining ses sion w as su pp lem en te d, sh ortly after th e con clusio n of th e sessio n , by Tekland r at d iet to m aintain th e r ats at their pre d eter m ine d w eigh ts.

App aratus T h e th ree sim ilar op er an t tra ining cha m bers m easu red 20 cm high , 21 cm lon g, an d 17.5 cm w ide. T h e fro n t an d rear cham be r w alls w ere con stru cted of alum inium . T h e sid e w alls an d ceiling w ere 0.6-cm w h ite tran slu cent an d c lear plastic, resp ectively. T h e ceiling w as ven ted w ith 0.6-c m -

362


d iam eter h oles. T h e cham ber ¯ oor w as com p osed of 0.3-cm -d iam eter stain less-ste el rod s sp aced 1.3 cm betw een cen tres. T h ese ro d s w ere ¯ oating w ith resp ect to th e ch am bers’ sid e w alls, th u s elim inating th e p ossib ility th at faeces an d u rin e d ep osited on th e w alls cou ld alter sh ock inten sity. A G erb ran d s m icrosw itch lever w as located o n th e right sid e of th e fro n t w all 6.9 cm above th e ¯ oor. A force equ ivalen t to 0.146± 0.195 N (15± 20 g) w as required to op erate th e lever. A feeder tro u gh w as m oun ted o n the extrem e le ft sid e of th e fro n t w all at ¯ oor level, an d a G erb ran d s feed er w as em p loyed to d eliver 45-m g N oyes ra t pellets into it. T h e ton e an d click s tim uli w ere p resented th rou gh an 8-o h m 20-cm sp eake r m ou n ted w ithin an en closu re centre d 20.6 cm above th e tr aining ch am ber. T h e ap p rox im ately 2000-H z to ne w as p resen ted at the 85± 90 d B ran ge. T he clicks w ere pre sen ted at a rate of ap prox im ately 10/sec at abou t 75 d B. S oun d inten sities w ere m easure d w ith th e m icro p ho ne p ar allel to th e sp eaker an d just above the lever. W ith th e exh au st fan op erating , th e am bien t n oise level w as ap p rox im ately 70 d B. T h e to n e an d click stimu li were p ra ctically inau d ible ou tsid e the attenu atio n chest. T h e ligh t stim ulu s em p loyed in train ing an d testin g w as gener ated by tw o 15- cm , 25-W, 120-V tub u lar sho w case bu lbs, each h oriz on tally m ou n ted 10 cm from th e tran slu cent sid e w alls. T h ese tw o 2 bu lb s p ro d u ced ap pr oxim ately 130 cd/ m w ith th e p h otom e ter po sition ed 12.5 cm fro m , an d d irected at, th e cha m be r’ s side w all. A sh ielded 7-W, 120 -V n ightlight bu lb op er ating at 3 W ser ved as a h ou selight an d w as o n con tinu ou sly. T h e illum ination it p rod u ced w as too d im to activate th e ph otom eter, bu t it n on etheless allow ed th e exp erim en ter just to d iscer n th e su bject w ithin th e ap p ar atus. T h e tr aining cham ber an d its asso ciated stim ulu s p resen tatio n d evices w ere en closed w ithin a so u n d -atten uation ch est d escribed elsew h ere (Weiss, 1970). S olid-sta te pr og ra m m ing equ ipm ent w as located in a ro om ad jacen t to th at h ousin g th e tr aining ch am ber s. C on stan t-cur ren t sh ock w as gen era ted by L eh igh Valley E lectro n ics 1531 sho ckers an d w as delivered to th e g rid ¯ oor, m an ipulan d u m , an d fro n t an d rear w alls th ro u gh its asso ciated scram bler.

Procedure Interincentive Training:

Fo od an d S hock Avoidan ce

T h e p ro g ressio n of step s u sed in train ing to establish stim ulu s con tro l for th is g rou p are pre sen ted sch em atically in Table 2, w ith th e p ro ced u res described in greater d etail in th e text. S tep 1. I nitia l S hock E sca pe a nd A voida nce Tra ining. T h e r ats w ere initially tra ined to escap e, an d su bs eque ntly to avoid, tr ains of br ief, 0.4± 0.6-se c, 0.6± 0.8-m A sh ocks by bar pre ssin g. A freeop eran t avoidance (FO A ) con tingenc y w as th en institu ted w h ereby resp on ses p ostp o ned 0.4-se c sh oc ks by 25 sec (R S 25 sec), w h ile, in th e absen ce of respo nd ing, sh ocks w ere d elivered every 3 sec (S S 3 sec). O ver 2± 3 sessio n s, th e S S inter val w as g rad u ally increased to 5 sec, w here it rem ained for the d u ration of th e expe rim ent. W h en a r at w as exh ibiting so m e p ro ® cien cy at avoidan ce u n der RS 25-se c S S 5-se c, to d iscou r age sh ock- p ro m pted ``e scap e’ ’ resp on ses, bar p resse s em itted d u rin g a sho ck w ere sch edu led to reset the s ho ck d u ration tim er. Training contin ued u n til respo ns e ra tes stab ilized and th e rats w ere avoiding at least 75% of th e m axim u m p ossible sh ocks calculated fro m th e R S 25-se c con tingen cyÐ tha t is, th ey w ere receiving 0.6 sh ocks/ m in (60/25 3 0.25) or less. H alf th e r ats h ad C con tinu ou sly on d u rin g these sessio n s. For th e othe r h alf, T w as on . (O n e rat w as elim inated at th is sta ge of tr aining becau se it cou ld no t be taug h t to avoid sh ocks in 4 train ing sessio n s.)


363

TABLE 2 In terin c en tiv e T rain in g : F o o d a n d S h o c k A v o id a n c e

Discrimina tive S timuli S tep

Tone*

Click

CL

TCL

1a 1b 1c

shoc k escap e RS 25- sec S S 3 ® 5 sec RS 25-se c S S 5-sec Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

2

RS 25-se c S S 5-sec

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

3a 3b 3c

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

magazin e training shap ing VI 15 ® VI 22- sec

4

Ð

Ð

Ð

VI 22-sec

EX T

5


VI 22-sec

EX T

6


VI 30-sec

EX T

Ð

EX T Ð

S essions 1± 2 2± 3 to criterio n (2± 15) to 6: 1 DR (m in 5) (5± 12) 1± 2 1 2± 5 to 8: 1 D R (2± 8)

Ð

EX T

(2± 6) to criterion** S -10/ 22 ; S -15/ 19 ; S -16 /31; S -19 /19

Tes t 1: Com pou nding excitor s an d inhibitor s: 12 block-r an dom ized 60- sec presentatio ns of T, C, an d TL , with T CL separatin g stim uli. Retu r n to Ste p 6 baseline for app roxim ately 6 sessions. Tes t 2: Com pou nding Excitor s: 12 block- random ized 60-sec presentation s of T, C, an d T C, with TC L separating stimuli. * To cou nterbalance co ntingencies acr oss stimuli, in Step s 1 an d 2 half th e subjects receive d avoid an ce train ing in ton e an d half in click. T hen in S tep 3 th ey were switch ed to th e oth er stim ulus an d foo d. Th us, half the rats had click as th e oc casio n to ear n food and half as th e occasio n to avoid shock. ** Five criteria described after S tep 6 in the M eth od section for th is g roup. S± X /Y = subject± number (X )/S tep 6 sessions to crite rio n (Y ). Note: RS 25-sec SS -5 sec = free-operant shoc k avoid an ce wherein th e response± shock (RS ) interval is 25 sec an d th e shoc k± shock (S S) inte rval is 5 sec; VI = variable interval; EX T = extin ction ; Ð Ð Ð = stimulus not presented ; T = to ne, C = click; CL = click + ligh t; T L = to ne + ligh t; TC = ton e + click; D TC L = absen ce of ton e, click, an d ligh t; DR = discrim inatio n ratio betwe en rates in S an d EX T con dition s.

S tep 2. A voida nce Discrimina tion Tra ining. A fter a rat h ad satis® ed the avoidance criterio n d escr ibed above for at least o ne sessio n , a tw o-com p on en t m ultiple (mult) sch ed u le w as instituted . F OA w as p ro g ram m e d d u rin g th e stim u lus p resen ted in S tep 1 (T or C ), but no t w h en th is stim ulu s w as abs ent (e xtinction ). T h e m ean du r ation of th e F O A com p on en t w as ap p rox im ately 3 m in, an d the m ean d u ration of th e extinction (E X T ) com p on en t w as ap p rox im ately 6 m in. For all gro u p s in all p ha ses of train ing, com p on en ts varied in d u ra tion , w ithin an d b etw een sessio ns, w ithin lim its th at ran ged fro m abou t 0.5 to 1.5 tim es th eir m ean value. T h ese sessio n s w ere abou t 6 h r lon g an d w ere ru n o n alter n ate d ays. Training con tinued on th is mult R S 25-se c SS 5-se c E X T sch ed ule u ntil th e rate in th e FO A com p on en t w as at least 6 tim es th at in th e extinction com p o nen t for 2 sessio n s, w ith a 5-se ssio n m inim um .

364


S tep 3. Food Tra ining. A ll of S tep 3 train ing oc cur red in th e p resen ce of th e stim ulu s n ot D p rese nted to th e rat in S tep s 1 an d 2Ð for exam p le, if T h ad b een its S for FO A , C w as n ow p rese nted co ntinu ou sly. W ith th e b ar rem oved, an d in th e p resen ce of th is n ew stim ulu s, th e r ats w ere tr ained to ap pro ach th e food tr ou gh w h en th e feed er op era ted . Food p ellets w ere p resen ted o n a variable-tim e (V T ) 90-se c sch ed u le u n til ap p roa ch an d ingestion w ere p ro m p t u p on feeder op era tion . O n th e next sessio n , th e bar w as replaced , an d th e ra ts w ere m anu ally tra ined to pre ss it th ro u gh the p ro cedu re of s uccessiv e ap p rox im ation s. A fter ap p roxim ately 50 reinforcem en ts on a con tinu ou sreinforcem en t sch ed u le, a r at w as shifted to a V I 15-se c sched u le th at w as g rad u ally increased to V I 22-se c. T h e lim its of the V I sch edu les w ere 2 sec to 3± 4 tim es th e m ean value, w ith inter vals sequ enced so as to keep th e len gth of any interv al ind ep en d ent of th e p receding interv al. T h ese an d su bsequ ent food-o nly sessio n s en d ed w h en ap prox im ately 130 p ellets h ad been ear n ed . S tep 4. Food Discrimina tion Tra ining. W ith th e com p o nen t d u ration s d escribe d for Step 2, a r at w as ru n on a mult V I 22-se c EX T sch ed u le un til it achieved at least an 8: 1 d iscrim inatio n ratio for 1± 2 sessio ns. W ith the intro d u ctio n of food d iscrim inatio n tr aining, u near ned food reinforcers in any com p on en t w ere n ot car rie d to th e n ext V I com p on ent, althou gh tim e accu m ulated into an interval w as sav ed . S tep 5. C ombined Food a nd A voida nce Tra ining. T h e tw o-com p on en t sch edu les d escribe d in S tep s 2 (mult RS 25-se c S S 5-se c E X T ) an d 4 (mult V I 22-se c E X T ) w ere com bined into a th reeD com p on en t mult V I 22- sec RS 25-se c S S 5-se c E X T sched u le. W h en T w as th e S for th e V I D con tingen cy, C w as th e S for F O A , w ith stim u lus± sch ed ule com bination s cou nterb alanced ove r su bjects. A s in p reviou s p h ases w ith F OA , at th e com m en cem en t of an F O A com p on ent, the R S interv al w as sch ed u led . In the absen ce of T an d C (T C ), n o con tingen cy (extinction ) w as p ro gr am m ed . C om p on en t d ur atio n s w ere com p ara ble to th ose in S tep 2. Se ssio ns w ere abou t 4 h r in d ur atio n. S tep 6. Fina l B a seline Tra ining S chedule. T h e con d ition ed inh ib itor w as establish ed by ad d ing a click-p lus-ligh t (C L ) period , in w h ich extinction w as p ro g ram m ed, to th e thre e-com p on en t sch ed u le d escr ibed in Step 5. T h is created a fou r-c om p on en t mult V I 30-se c R S 25-se c E X T E X T sch edu le. W h en C alon e w as pre sen ted, th e V I or F O A con tingen c y, as ap p ro p riate for th e p articular su bject, w as still effec tive. (W h en a T or C com p o nen t en d ed , the con d ition a rat w as n ow in, the absen ce of T, C an d light (L ), is d esign ate d as T C L .) T h e L cou ld be add ed to C at any tim e, w ith C L even, o n occasio n , d irectly following T C L . T his is th e p ow erfu l A + /A B 2 m eth od of creating an inhibitor. T h e C com po n ent w as n ow 4± 5 m in in d u ration , o n avera ge, w ith T, C L , an d T C L 2± 3 m in, o n ave rag e. Tra ining Criteria . Training con tinu ed on th e ter m inal baseline sch ed ule u ntil, for at least th ree con secutive sessio n s, after 30-m in w ar mu p : (1) resp on se rates in th e V I an d F O A com p on en ts w ere D sta ble, and no m or e th an seve ral resp on ses/m in differen t from each oth er, (2) r ates in T an d in C S s w ere clearly d ifferen t fro m th ose in T C L , w ith a d iscrim inatio n r atio of 10: 1 so u gh t, w h ere p ossible, (3) rates in C w ere at least 10 tim es tho se in C L , (4) sh oc k r ates in F O A w ere 0.6 p er m in or less, an d (5) respo n din g com m enc ed p rior to a sh ock pro m p t in at least 75% of th e F O A com p on en ts. To satisfy th ese criteria, esp ecially (1), it w as n ecessary to m an ipu late V I values, food d ep rivation , R S interv als, and /or sh oc k inten sities. W h en a su bject sa tis® ed th ese criteria, Test 1 w as ad m inistered . (Fou r su bjects w ere eliminated at th is sta ge of tr ainingÐ tw o becau se the y requ ired sho ck pro m p ts to com m en ce resp on din g in th eir F O A com p on en ts, o n e becau se its r ates in T C L w ere too high , an d on e becau se of a train ing erro r.)


365

Test 1: C ompounding E xcitors with I nhibitors. T, C , an d ton e-p lus-light (T L ) w ere pre sen ted in each of 12 block-ran d om iz ed rep lication s. T C L sep ara ted th ese stim uli. A ll pr esen tatio ns w ere 1 m in, m aking th e test 72 m in lon g. A repre sen tative test block cou ld con sist of th e follow ing sequ ence of stimu li: T, T C L , T L , T C L , C , T C L . A nim als were given ap p roxim ately 30 m in w ar m u p on th eir baseline tr aining sch ed ule p rior to testin g, b ut all con tingen cies w ere d isco ntinu ed d u ring the test. A fter Test 1, an im als w ere retu r n ed to th eir ® n al baseline sch ed u le described in S tep 6, ab ove, for ap p rox im ately 6 sessio n s. Test 2 w as th en ad m inistered .

Test 2: C ompounding E xcitors. O n e-m in T, C , an d ton e-p lus-c lick (TC ) p eriod s w ere pre sen ted in e ach of 12 block-ran d om iz ed r eplicatio ns, w ith 1-m in T C betw een th ese stim u li. A rep resen tative test block cou ld co n sist of th e follow ing sequ ence of stimu li: T, T C , T C , T C , C , TC . A n im als w ere given ap p rox im ately 30 m in of their base line train ing sch ed u le prio r to testing, bu t all con tingen cies w ere d iscon tinue d d u ring th e test.

Intraincentive Training:

Fo od

T h e p ro g ressio n of step s u sed in train ing to establish stim ulu s con tro l for th is g rou p are pre sen ted sch em atically in Table 3, w ith th e p ro ced u res described in greater d etail in th e text. S tep 1. Food Tra ining. T h is m ag azine train ing an d bar p re ss sh ap ing w as p ro ced ur ally like th at d escr ibed in S tep 3 for th e interin cen tive g ro up s. S tep 2. Food Discrimina tion Tra ining ( T or C) . T h is mult V I E X T tr aining w as like th at received by th e interin cen tive g ro up s as S tep 4. T h e V I com p on en t w as corre lated w ith th e stimu lusÐ T or C Ð p resen ted du rin g S tep 1. S tep 3. Food Discrimina tion Tra ining ( C or T) . T h e rats were n ext given a sessio n of V I 22-se c train ing in th e p resen ce of the stim u lusÐ C or T Ð th at h ad no t been p resen ted in S tep s 1 an d 2. D T h en , w ith th is stim ulu s as th e S , th ey were given mult V I 22-se c E X T sessio ns like tho se d escribed in Step 2. S tep 4. Food Discrimina tion Tra ining ( T a nd C ) . T he r ats no w p ro gr ess ed to a th ree-com p on en t mult V I 22 -s ec V I 22 -se c E X T sch edu le, w herein th eir discrim ination ratios reach ed abou t 10:1 or better. M ost w ere m aintained on th eir V I 22-se c sch edu les th ro u gh S tep 4, w ith T an d C V I com p on en ts 2± 3 m in in d u ratio n an d th e T C extinction com po n ents, o n avera ge, 5± 6 m in lon g. (O n e su bject w as ter m inated at this stag e of tra ining be cau se it w as accidentally r u n o n th e F OA sch edu le.) S tep 5. I nitia l Conditioned I nhibition Tra ining. Two to 3 sessio n s of tr aining w ere ru n w ith 2± 3 m in C com p on en ts alter n ating w ith 5± 6- m in C L com p o nen ts. T h e V I food sch edu le w as effective in C , an d extinctio n op er ate d in C L for su bjects 24, 26, an d 27. S u bject 28 wen t d irec tly to Step 6. S tep 6. Fina l B a seline Tra ining S chedule. T h e con d ition ed inhibitor w as ® r m ly establish ed d urin g th is ® n al sta ge of tr aining, in w hich th e rats w ere ru n o n a fou r-c om po nen t mult V I 30-se c V I 30-se c E X T E X T sched u le. C om p on en ts w ere sequ enced as described in Step 4, above. W hen T or C alon e w as p resent, the V I 30-se c sch ed u le w as in effec t. H ow ever, L cou ld be p resen ted at any

366

W E IS S , T H O M A S , W E IS S M A N TABLE 3 In tra in c e n tiv e T ra in in g : Fo o d


Tone*

Click

CL

TCL

1a 1b

mag. trn. + shaping VI 15 ® VI 22- sec Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

2

VI 22- sec

Ð

Ð

Ð

Ð

Ð

Ð

VI 22-sec VI 22-sec

Ð

Ð

Ð

Ð

Ð

Ð

Ð Ð EX T

VI 22-sec

Ð

Ð

Ð

EX T

3a 3b 4 5 6

Ð

Ð

Ð

Ð

Ð

Ð

VI 22- sec Ð

Ð

Ð

VI 30- sec

1± 2 2± 3

EX T Ð

VI 22-sec

EX T

VI 30-sec

EX T

Ð

Ð

S essions

Ð

EX T

to 6: 1 D R (4± 7) 1 to 8: 1 D R (1± 3) 6± 8 2± 3 to criterion** S -24/ 23 ; S -26/ 48 ; S -27 /14; S -28 /28

Tes t 1: Com pou ndin g excitor s an d inhibito rs: 12 bloc k ran dom ized 60- sec presentatio ns of T, C, an d TL , with T CL separatin g stim uli. Retu r n to Ste p 6 baseline for app roxim ately 6 sessions. Tes t 2: Com pou nding excitor s: 12 block ran dom ized 60- sec presentation s of T, C, an d TC , with TC L separating stimuli. * To cou nterbalance con tin gen cies across stimuli, in Step s 1 an d 2 half th e subjects received food train ing in ton e an d half in click. Th en in Step 3 they were switc hed to th e oth er stimulus. S tep s 4, 5, an d 6 were as presented for all subjects. ** T hree criteria described after S tep 6 in th e M eth od section for th is g roup. S± X /Y = subje ct± num ber (X )/S tep 6 sessions to criterion (Y ). Note: VI = var iable interval; EX T = extin ctio n; Ð Ð Ð = stimulus not presented; T = ton e; C = click; CL = click + light; T L = ton e + ligh t; TC = to ne + click; TC L = abs ence of ton e, click, an d ligh t; D DR = discrim inatio n ratio betw een rates in S an d EX T co nditions.

tim e du rin g th e C , c reating C L , d urin g w hich b arp ressin g w as ineffective (extinction ). T h e m ean d ur atio n of th e C com p on en t w as n ow 4, 4.5, or 5 m in, an d the m ean d u ratio n s of T, C L , an d T C L com p on en ts w ere 2 or 2.5 m in. T h u s, a r at w ould often star t a C com po nen t in C alo n e; th is w ou ld ch an ge to C L an d retu r n to C on ce or sever al tim es per com p on en t. W hen a ra t h ad d if® culty for m ing th e C /C L d iscrim ination , it w as retu r n ed to Step 5 for several sessio n s. Tra ining Criteria a nd Testing. Training con tinued on th e mult V I 30-se c V I 30- sec E X T E X T sch edu le u n til, for at least thre e co nse cu tive sesssio n s, after a 30-m in w ar m up : (1) resp on se rates in D the V I com p o nen ts w ere stable, w ith n o ap p aren t tren d , (2) r ates in T and C S s w ere clearly d ifferen t fro m th ose in T C L , w ith a d isc rim inatio n r atio of 10:1 so u ght, w h ere po ssible, an d (3) rates in C were at least 10 tim es th ose in C L . W h en a su bject satis® ed th ese criteria, it received a test iden tical to Test 1 d escribed for th e interin centive gr ou p.


367

A fter th is test, an im als w ere re tu r n ed to th eir ® na l baseline sch edu le for ap p rox im ately 6 sessio n s, after w hich th ey rece ived a test iden tical to Test 2 d escribed for th e interincen tive gro u p.

Intraincentive Training:

Free-O peran t S hock Avoidan ce

T h e p ro g ressio n of step s u sed in train ing to establish stim ulu s con tro l for th is g rou p are pre sen ted sch em atically in Table 4, w ith th e p ro ced u res described in greater d etail in th e text.

TABLE 4 In tra in c e n tiv e T ra in in g : S h o c k A v o id a n c e


Tone*

Click

CL

TCL

S essions

1a 1b 1c

S hock escape RS 25- sec S S 3 ® 5 sec RS 25-se c S S 5-sec Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

Ð

2


Ð

Ð

Ð

Ð

Ð

Ð

RS 25 -sec SS 5- sec RS 25 -sec SS 5- sec

Ð

Ð

Ð

Ð

Ð

Ð

Ð Ð EX T

1 2

RS 25 -sec SS 5- sec

Ð

Ð

Ð

EX T

to 10: 1 DR (5± 7)

3a 3b 4 5 6

Ð

Ð

Ð

Ð

Ð

Ð

RS 25-se c S S 5-sec Ð

Ð

Ð


EX T Ð

1± 2 2± 3 to criterio n (5± 7) to 6: 1 D R (3± 6)


EX T

Ð

Ð

1


EX T

EX T

to criterion** S -11/ 9; S -12/ 6; S -22/ 19

Tes t 1: Com pou nding Excitor s an d In hibitor s: 12 block random ized 60-s ec presentatio ns of T, C and TL , with T CL separatin g stim uli. Step 6 ter m inal baselin e for ap proxim ately 3 session s Tes t 2: Com pou nding Excitor s: 12 bloc k ran dom ized 60- sec presentatio ns of T, C and TC , with TC L separating stimuli. * To cou nterbalance co ntin gen cies across stimuli, in S tep s 1 an d 2 half the subjec ts received avoid an ce train ing in ton e an d half in click. Th en in Step 3 they were switc hed to th e oth er stimulus. S tep s 4, 5, an d 6 were as presented for all subjects. ** F ive criteria described afte r Step 6 in the M etho d sectio n for th is g roup. S± X /Y = subject± number (X )/S tep 6 sessions to crite rio n (Y ). Note: RS 25-s ec S S5-s ec = free-op eran t shock avoid an ce wherein th e respon se± shock (RS ) interval is 25 sec an d th e shock± shock (S S) inter val is 5 sec; EXT = extin ction; Ð Ð Ð = stimulus not presente d; T = ton e; C = click; CL = click + ligh t; T L = ton e + ligh t; TC = ton e + click ; TC L = abs ence of D ton e, click, an d ligh t; D R = discrimination ratio betwee n rates in S an d EX T co nditions.

368


S tep 1. A voida nce Tra ining. T h is w as th e s am e as S tep 1 for th e interin cen tive gro u p. (O n e r at w as elim inated at th is s tage of tr aining becau se it failed to avoid sh ocks after 4 sessio n s each of ap p rox im ately 4 h r.) S tep 2. A voida nce Discrimina tion Tra ining ( T or C) . interincen tive g ro u p.

T h is w as th e sam e as S tep 2 for th e

S tep 3. A voida nce Discrimina tion Tra ining ( C or T) . T h e r ats w ere n ext given o n e sessio n of R S 25-se c S S 5-se c train ing in th e p res ence of th e stim ulu sÐ C or T Ð n ot p resen ted in S tep s 1 an d 2. D T h en , w ith this stim ulus as th e S , th ey w ere given mult RS 25-s ec S S 5-se c E X T sessio n s like th ose d escr ibed in S tep 2. S tep 4. A voida nce Discrimina tion Tra ining ( C a nd T) . T h e r ats n ow p ro gresse d to a th reecom p on en t mult (RS 25-se c SS 5-se c) (RS 25-se c S S 5-se c) E X T sched u le, w h erein th eir d iscrim ination ratios reache d abou t 10:1 or better. T h e m e an com p on en t d ur ation in a given sessio n ran ged fro m 3.5 m in to 6 m in. Relative d ur ation s of F O A an d E X T com p on en ts w ithin a sessio n w ere d eter m ined for each su bject on the basis of the d e gree to w h ich th e sh ock-av oidan ce con tingen cy, p rog r am m ed in T an d in C , an d E X T, p ro g ram m ed in T C , w ere gaining ap p ro p riate beh aviour al con tr ol. (O n e su bject w as ter m inated at th is sta ge of train ing becau se it con siste ntly received m ore than 0.6 sh ocks/m in). S tep 5. I nitia l Conditioned I nhibition Tra ining. w ith 5± 6-m in sh ock- free C L com p on en ts.

H ere, 2± 3 -m in F OA C com p on ents alter n ated

S tep 6. Fina l B a seline Tra ining S chedule. T h e con d ition ed inhibitor w as ® r m ly establish ed d urin g th is ® n al sta ge of tra ining. T h e r ats were ru n on a fou r-c om p on en t mult (RS 25-se c S S 5sec) (R S 25-se c S S 5-se c) E X T E X T sch edu le. W h en T or C alon e w as pre sen t, th e R S 25-se c S S 5sec con tingen cy w as in effect. H ow eve r, L cou ld be p resented at an y tim e d u ring th e C , creating C L that w as sh ock-fre e (extinction ), as T C L w as. O ver sessio n s, m ean com po n ent d u ration s r an ged as follow s: C , 4± 6 m in; T an d C L , 2± 3 m in; an d TC , 1.5± 4 m in. H ow ever, d u rin g any sessio n , th e ave rag e C L d u ratio n w as h alf the avera ge C d u ratio n. W h en a ra t h ad dif® culty for m ing the C /C L d iscrim ination , it w as retu r n ed to S tep 5 for several sessio ns. A n im als w ere train ed on alter n ate d ays in 5± 6 -hr sessio n s u n til th ey m et th e d iscrim ination criteria d escribed b elow. S ho ck intens ities ran ged fro m 0.8± 1.2 m A . Tra ining Criteria a nd Testing. Training con tinu ed on th e ® n al b aseline sch edu le u n til, for at least th ree cons ecu tive sessio ns, after a 30-m in w ar m u p : (1) resp on se rates in th e F O A com p on D en ts w ere sta ble, w ith n o ap p aren t tren d , (2) rates in T an d in C S s w ere clearly differen t from tho se in T C L , w ith a d iscrim inatio n ratio of 10:1 so u gh t, w h ere po ss ible, (3) rates in C w ere at least 10 tim e s tho se in C L , (4) sh oc k rates in FO A w ere 0.6 p er m in or less, an d (5) r esp o nd ing com m en ced p rior to a sh ock pr om p t in at least 75% of the FO A com p on en ts. W h e n a su bject satis® ed th ese criteria, it received a test identical to Test 1 d escribed for th e interin cen tive gr ou p. A fter Test 1, an im als w ere retu r ne d to th eir ® n al baseline for ap p rox im ately 3 sessio n s, after w h ich th ey received a test iden tical to Test 2 d escrib ed for th e interincen tive g rou p.


369

R esu lts Criterion B aselin e B ehaviou r Table 5 presents criterion b aseline respo nse rates in T, C , C L , an d T C L for all su bjects. T he baseline rates in T an d C w ere gener ally h igher for the ap petitive intraincentive rats than for the aver sive intraincentive rats, but the rates of S ubjects 22 an d 28 overlap. A lthough rates of the in terin centive rats overlap those of both intraincen tive g roups, they are generally closer to those of the aversive intraincentive rats. In all subjects, save 16, rates in T an d C w ere w ithin 1± 2 respo nses/m in of each other. A ll subjects practically ceased respo ndin g in C L , w hich u sually co ntrolled fewer than 0.5 responses/m in an d alw ays less th an 10% of the rate s occasioned by C alone. C L co ntain ed a stimulus (C ) that co ntinued to m aintain response rates com parable to D those of the T S . N evertheless, in all 11 sub jects, rates in C L w ere lower than Ð an d usually h alf ofÐ those in T C L , the other extinction-correlated stimulus [t(10) = 5.3 3, p < .00 1]. Rates in T an d C were at least 10 tim es those in T C L fo r 9 of the 11 sub jects, an d seven times high er for Sub jects 27 an d 28. Figure 1 presents a 1-hr segm ent from a representative criterio n± sessio n cum ulative record for a rat from each g roup, ap petitive intraincentive (Subject 18), aversive intrain-

TABLE 5 C rite rio n B a s elin e R a tes (R e s p o n s e s /M in u te)

S timuli Group

S ub

C

T

TCL

CL

Intrainc entive G ro up (A ppetitive)

24 26 27 28 X

19.5 11.2 10.7 6.9 12.1

18 .0 13 .2 12 .3 7.5 12 .8

1.3 0.7 1.5 1.0 1.1

0.4 0.3 0.7 0.6 0.5

Intrainc entive G ro up (Aver sive)

11 12 22 X

4.8 5.3 7.5 5.9

4.8 5.7 8.5 6.3

0.5 0.3 0.7 0.5

0.1 0.2 0.2 0.2

VI

FOA

TCL

CL

0.5 0.7 0.7 0.5 0.6

0.3 0.6 0.3 0.2 0.4

Interincentive G roup (A ppetitive/ Aver sive)

10 16 15 19 X

6.6* 10.3* 8.4 6.7 8.0

6.0 7.0 8.0* 6.2* 6.8

N ote: C = click; L = ligh t; TC L = absen ce of to ne an d click; VI = variable-inter val food schedule; FOA = free-operan t avoid an ce of shock schedule; * denotes com po nent signalled by ton e; TC L an d CL were alw ays assoc iated with extin ction , S ub = subject number.

370


FIG . 1.

One-hr segme nts from represe ntative criterion session cumulative records for rats from the appetitive intraince ntive group, aversive intraincentive group, and both stimulus± schedule combinations of the interincentive group. Four sc hedule com ponents are presented in these records: T (pen in upper re gister with no overbar), C (pen in upper register with thin overbar), CL (pe n in upper register with heavy overbar), and TCL (pen in lowe r re gister). Slash marks indicate food pre sentations in variable-interval (VI) schedule components and shocks in free -operant avoidance (FOA) components. Contingencie s ope rating in T and in C indic ated for each subjec t. During CL and TCL the rats were in extinction.

centive (Subject 11), an d both stimulus± schedule com binations of the interincen tive g roup (Subjects 16 an d 19). Response patter ning, re¯ ected by the ® n e gr ain of the records, w as com parab le in T an d in C for intraincentive an d interincentive subjects. Barpressing com m enced upo n the onset of T an d of C an d ceased abruptly in C L an d TC L . T here w as at least 1, an d often 2, L presentations during each C period. T he L could be su perim posed at the onset of C (initial C com ponent for Su bject 28), after C had been on fo r a short tim e (4th and 5th C co m ponents for Subject 28) an d /or close to the end of a C period (6th C com ponent for Subject 28). B ehaviour shifted abru ptly w hen conditions chan ged from C to C L or from C L to C . A lthough L effectively eliminated responding w hen superim posed on C , C alone occasio ned respo nding com parably to T.


Test 1:

371

C om pou nding Excitors w ith Inhibitors

T he respo nse rates of each rat in each condition of Test 1 are presented in the upper pan el of Figure 2. T he light reduced responding in T m ore dram atically for the intraincentive g roups (by 94.4% for the ap petitive g roup an d 100% for the aversiv e g ro up) than for the interincentive g rou p (50.2% ). Responses em itted in T L , as a percentage of those em itted in T, are presented for each su bject in the lower pan el of F igure 2. T his reduction by L , of responding occasio ned by T, for 3 of th e 4 rats in th e ap petitive intraincentive g roup w as w ith in 1± 2% of the reduction L produced in all 3 aversive intraincentive rats. T herefore, the ap petitive 1 an d aversive intraincentive g roups were com bined for further an alysis. L reduced responding occasioned by the excitor T signi® can tly m ore in the com b ined intraincentive g roups than it did in the interincentive g rou p, t(9) = 3.64, p < 0.01. Test 2:

C om pou nding Excitors

The response rates of each rat in each condition of Test 2 are presented in the upper pane l of Figure 3. T C controlled m ore responding than T or C alone for 6 of the 7 intraincentive subjects, a response enhan cem ent not produced by T C in any interincentive subject. T he overall test rates of the ap petitive intraincentive rats w ere clearly higher than those of the aversive intraincentive rats. H ow ever, these rats could be com pared if Test-2 rates in T C w ere presented as a percentage of each subject’s highest-rate single stimulus (T or C ). T his rela tive TC ra te is show n in the low er pan el of F igu re 3. A p ercentage over 100 indicates the deg ree to w hich T C occasioned a g reater resp onse rate than th at gover ned by the elem ent w ith the h ighest rate. A percentage b elow 100 in dicates the deg ree to w hich responding in T C w as lower than that in the highest-rate elem ent. T he intr aincentive g roups w ere com bined as (1) the relative T C rates of the intraincentive groups overlap, (2) 3 of the 4 ap petitive-intraincentive-g roup rats an d all 3 of the aversive-intraincentive-g roup rats produced add itive sum m ation, (3) the relative T C rates of the ap petitive (142% ) an d aversive (197% ) intraincen tive g roups w ere not signi® can tly different, t(5) = 1.25, p > 0.25 , an d (4) the low test rates of the aversive intraincentive g roup to T an d C probably in¯ ated their relative T C rates. T he com bined intraincentive g roups’ relative TC rate (165% ) w as signi® can tly g reater than 100, t (6) = 2.85, p < 0.03, the ratio indicating eq uality of the rates in T C an d the single stimu lus controlling the highest test rate. It w as also high er than the 67% relative T C rate of the interincen tive g roup, t(9) = 3.05, p < .02). T h e 67% relative T C rate of the interincen tive g roup w as clearly in the opposite d irection to 165% of th e intraincentive g roups. H ow ever, the 67% w as n ot signi® can tly less than 100, t(3) = 2 2.68, p = 0.075).

1

In Test 1, TL occasio ned z ero respo nses for all 3 aversive ± intrain c entive rats. This lack of varianc e preclu ded a param etric statistic al test to determ in e wh ether ap petitive and aversive intrain c entive g rou ps were differe nt or comp arable. In ad dition, w ith only 3 aversive intrain centive rats, there is no non -param etric test that cou ld yield a sign i® cant diffe ren ce. N everthele ss, combin in g the intrain centive gro ups se em ed justi® able on the basis of the fact that for 6 of the 7 in train centive an im als, L red uced T-occasion ed re sp ond ing by percen tages that were obviou sly behavio urally comp arable : 98% , 99.2% , 99.2% , 100% , 100% , and 100% .

372


FIG . 2 .

Upper panel: Response rates of each rat in each condition of Test 1. Lower panel: Individual and group mean pe rcentage of Test 1 responses emitted in TL, relative to the number emitted in T, for appetitive intraincentive , aversive intraincentive , and interincentiv e-trained subje cts. 100 represents equality of T and TL rate s. No te: C = click; T = tone; TL = tone-plus-lig ht; TCL = absence of tone, click, and light; VI = variable-interval food schedule; FOA = free-operant avoidance of shock sc hedule; * denotes component signalle d by tone. Test was performed in extinction.

D iscussio n Test 1:

C om bining Excitors W ith Inhib itors

In all g roups, L occasioned response cessatio n an d w as co nditioned as an inhibitor though th e A + / A B 2 p arad igm . W hen L w as from the sam e incentive class that w as oper ating to m aintain responding in T (intraincentive g roups), L profoundly reduced Toccasio ned responding. T his reduction w as 10 0% for all av ersive-intraincentive-g rou p rats, an d 98± 99% for three of the four ap petitive-intraincentive-g roup rats. T he m ean reduction for this latter g roup w as 90.6% . W hen L w as conditioned as an inhibitor from the incentive class op posite to that m aintaining respo nding in T, L reduced T rate by only 50.2% , com pared to the signi® can tly greater 94.6% reduction fo r the com bined intraincentive g roups. T his large difference between groups is clearly in the direction p redicted by ap petitive± aversive interaction theory. T his is o nly the second direct con® r m ation , through a su m m atio n test, of ap petitive± aversive inter action theory’ s postulation that excitors an d inhibitors from opposite incentive classes are m otivation ally com plem enting. T he ® rst w as reported by G rossen, K ostan sek an d Bolles (1969). G rossen et al. (1969) dem onstrated that an in hib itor from the opposite incentive class (appetitive) to that energizing b eh aviour (aversive) increased operan t rate, w hereas an ap petitive excitor reduced avoidan ce (reciprocal inhibition). T hey trained rats on freeoper an t avo idan ce (FO A ) in a shuttle box. A ppetitive classical co nditioning w ith a tone


373

FIG . 3 .

Upper panel: Response rates of each rat in each condition of Test 2. Lower panel: Individual and group mean pe rcentage of Test 2 responses emitted in TC, relative to those emitted in the highest-rate element (T or C). Percentages above 100 indicate greater responding to TC than to T or C (additive summation). Percentages below 10 0 indicate that TC was not the test component controlling the highest rate. N ote: C = click; T = tone, TCL = abse nce of tone, click, and light; VI = variable -interval food schedule ; FOA = freeoperant avoidance of shock schedule; * denotes component signalled by tone. Test was performe d in extinction.

C S followed in a different cham ber. T he ton e w as then presented to the rats w hile they were avoiding shock. O ne g roup received tone± food p airings (C S+ ), an d for an other g roup tone signalled the absence of food (C S 2 ). C om pared to the effect of tone o n FO A rate for control g roups, for w hom tone an d food presentations w ere unrelated or tone w as never presented, FO A decreased in C S+ an d increased in C S 2 . In the current experim ent, all proper ties acquired by a stimulus w ere established as a prod uct of the respon se an d reinforcem ent rates engendered by the operan t contingencies prog ram m ed on the four-com p onent m ultiple-sch edu le baselines. In com parison, in the design used by G rossen et al. (19 69), the ap petitive excitors an d inhibitors w ere classically co nditioned off their FO A b aseline. T hus, it is highly unlikely that their C S occasio ned behaviour incom patible w ith shuttling (their F OA operan t) any w here near as pow erfully as L occasioned behaviour incom patible w ith barpressing (speci® cally, barpress cessation) in th e present exp eriment.

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T he nature of the con¯ icting behaviours occasion ed by T an d by L m ay help explain w hy the interincentive g roup’ s T L rate, although signi® can tly higher than that of the interincen tive g roup, w as not g reater than the rate occasioned by T alo ne. A s explained in the introduction, these are the results that Weiss’ (1978) two-factor m odel w ould lead one to expect for the interincentive relative to the intr aincentive g rou p. T hat m odel co nsiders both the d iscrim inative response an d incentive processes established on these baselines w hen predicting test outcom es. H ow ever, o nly higher rates in T L than in T by the interincen tive g roup w ould un eq uivocally support ap petitive± aversive interaction theory. O ne could m ake th e ad h oc assum p tion th at inhibitors tran sfer across excitors of the sam e class b ut show neither ex citatory nor inhibitory tran sfer to an excitor of th e op posite reinforcem ent class. A cco rdin g to this alter native incentive m odel, for the intraincentive g roup during T L , the resp onse red uction occasion ed by L as w ell as L’ s m otivationally inhibiting p roperties would be acting to reduce respo nding. In com pariso n, for the interincen tive g rou p, only the respo nse reduction occasioned by L w ould be operatingÐ hen ce the patter n of Test-1 results. T he credibility of this explanatio n w ill be exam ined from two perspectives. First, evidence that opposes the assu m ption that inhibitors of the opposite incentive class are effectively ``neutral’ ’ w ill b e exam ined. Second , the tests of three oth er pred ictions from ap petitive± aversive interaction th eory that w ere design ed in to the present experiment as system atic replications w ill be d iscu ssed. If the ad hoc assum p tion described above is corre ct, all the indirect evidence presented in the introduction suggesting that an excitor of one incentive class has affective properties in com m on w ith an inhibitor of the opposite incentive class is brought into question. T his eviden ce included co n® r m ations from superconditioning (D ickinson , 1977), blocking (D ickinson & D earing, 1979), condition ed rein forcem ent (L eitenberg, 1965), an d co nditioned pu nishm ent (L oL ordo, 1969) studies. In ad dition, it is not scien ti® cally justi® ed, or parsim on ious, to argue that som e unique, special, u nproven m otivatio nal process w as responsible for the Test-1 results w hen that process is at basic variance w ith ap petitive± aversive interaction theory an d Weiss’ (1978) two-factor m odel of stimulus controlÐ m odels that in teg rate vast quan tities of data. To assay the inte grity of the cu rrent procedures, the present study w as designed such that Tests 1 an d 2 could system atically replicate a spectrum of ap petitive± aversive interactio n theory predictions. T hese replicatio ns w ere successful, further validating the notion that ou r operations w ere co ntacting these m otivatio nal p rocesses. A dditive su m m ation w as produced w hen excitors for the sam e incentive class were presented simultaneo usly (Test 2, intraincentive groups). C om pounding excitors an d inh ibitors from the sam e class pro duced response averaging (Test 1, intraincentive g roups). W hen excitors from opposite incentive classes w ere presented simultaneou sly, dram atic evidence of reciprocal inhibition w as revealed (Test 2, interincen tive g roup ). In add ition, the Test1 results w ere co nsistent w ith those of G rossen et al. (1969), ev en though in th e current ex periment profound re spo nse com petition p robably kept th e superimp osition of an inhibitor of the opposite incen tive class from producing g reater responding than the ex citor alone. S o it seem s that the ad hoc explanation of the Test 1 results, alth ough log ical, can be safely dism issed . N evertheless, the reduction in Test 1 T L rate due to the response process alo ne should be m easured. T hen the m otivatio nal effects of an inhibitor


375

of the opposite incentive class could be isolated in the circum stances of the current 2 ex periment. Weiss an d Schindler (1985) trained rats on an avoidan ce baseline that had m an y sim ilarities to that of the aversive intraincentive g rou p of the p resent study. N evertheless, in testing, T L controlled ap proxim ately 30% of the rate occasioned by T, w hereas for the aversive intraincentive g roup of the present study L reduced responding occasio ned by T co m pletely. W hy? T he g reater inhib itory strengthÐ both response-discriminative an d m otivationalÐ acq uired by L in the present experim en t than in Weiss an d S chindler’ s can be attributed to the C + /C L 2 parad igm used here to condition inhibition. Fo r the intraincentive g roups of the present experim ent, (1) L w as conditioned as an inhib itor w ithin the ex citatory C co ntext, an d (2) L occasio ned an actual reduction in b arpressing. In com parison, in the Weiss an d S ch indler (1985) study, su bjects postpo ned shocks in T, as in the current experim ent, w hereas L an d the simultaneous absence of T an d L (T L ), w hich were shock-free, controlled negligible respo nding. T herefore, (1) L w as co nditioned as an inhibitor w ithin the m inimally excitatory context of the cham b er as a w hole, w hich w as not excitatory enou gh to occasio n avo idan ce in T L , an d (2) L , w hich alw ays followed T L , w as the o ccasio n to not com m ence responding. In com parison, L actively occasio ned response cessatio n in the present experim ent. T h is h ad to co ntribute to L’ s cap acity to reduce T-occasion ed responding in the intraincentive g roup alm ost com pletely in Test 1. Test 2:

C om bining Excitors w ith Excitors

In Test 2, for th e interincen tive group, stimuli w ere com p ou nded that occasio ned barpressing w hile b eing excitors from opp osite incentive classes. C om pou nded opposing ex citors here com pletely overwh elm ed the add itive su m m ation that the respo nse factor oper ating alo ne w ou ld produce in such situations (Weiss, 1971, Ex p. 2). O n average, TC occasio ned rates inter m ediate to those occasioned by T or C alone, w ith no rat em itting m ore respo nses in T C than its highest rate in a single stimulus. T hese results are conD sisten t w ith those reported by Weiss an d S chin dler (1989) w hen they com pou nded an S that occasioned food-m ain tained respon din g w ith one that occasioned FO A -m aintained responding. T he reciprocal inhibition predicted by ap petitive± aversive interaction th eory 2

T he fou r-comp on ent m ultip le sche dule baselin e deve lope d for the pre sen t experim ent m igh t be m od i® ed to m easu re the deg ree to w hich L’s resp on se cessation discrim in ative function alone would re duce T-occ asion ed respon din g. In that design , resp ond in g wou ld be main tain ed by a V I food sch edule in T an d in C , w ith extinc tion program m ed in TCL , as for the app etitiv e in train centive g roup of the pre sen t e xp erim ent. H owever, in CL a differential-rein forcem ent-of- othe r-behav iour (D RO) c ontin genc y wou ld op erate wh ere in food rein forcers were delivere d, at a rate com parable to that occur ring in C , if the rat refrain ed from barpre ssin g. Thus, in the propose d expe rim e nt, CL would occasio n a respo nse re duction com parable to that of CL in the pre sen t exp erim ent. H owever, as P (reinforcem ent|C) = P (rein forc em ent|CL), inh ibitory in centiv e-m otive prope rties shou ld not be con dition ed to L, on ly in hibitory re sp onse discrim in ative proper ties. Follow in g this no n-differential incen tive train in g, whe re L is only discrim in ative for a red uction in resp on din g, L shou ld redu ce respon ding m ain tain ed by T alone by (1) signi® can tly m ore than the 50% repo rte d for the interin centive group in the presen t exp erime nt (wh ere L was an in hib itor of the opp osite in centive c lass to that energizin g barpre ssing in T), an d (2) signi® can tly le ss than the essentially com plete cessatio n rep orted for the intrain centive g rou ps of the pre sen t expe rime nt (for wh om L w as an in hibitor from the sam e inc entive class as that energizin g barp ressing in T).

376


w hen excitors from the opposite incentive class are presented simultaneously w as supported, w ith that in hib ition ap pearing even m ore pro foun d in the present experim ent than that reported by Weiss an d Schindler (1989). In Test 2, for the intraincentive g roups, stimuli were com p ounded that occasio ned barpressing an d w ere excitors from the sam e incentive class, conditions that should be m otivatio nally au gm enting. Fo r these intraincentive g roups, T C occasioned a signi® can tly higher percentage of test respo nses than did (1) their highest-rate single stimulu s, or (2) the percentage occasio ned by TC for the interincen tive group. A g ain the dynam ics of ap petitive± aversive interactio n th eory w ere con® r m ed, altho ugh the add itive su m m atio n co ntrolled by T C for the intrain centive g roups w as less th an that previously reported D under sim ilar response-occasioning an d incentive co nditions w hen the S s w ere from different m odalities (e.g. E m urian & Weiss, 197 2; Weiss, 1971, E xp. 2). T his m ight b e due to the fact th at (1) tone an d light w ou ld m aintain th eir integ rity w hen com pounded, w hereas tone an d click m ight coalesce, an d (2) in the p resent study, the click’ s excitatory prop erties m ight have been diminished through its association w ith the inh ib itor, L . In any event, in the presen t experiment, w hen two excitors from the sam e incentive class were com pounded, clear ad ditive sum m atio n w as produced, even th ou gh characteristics of the current intraincentive training procedures probably attenuated that phenom eno n som ew hat. Conclusion M ow rer’ s (1947) po stulation of two-factor learn ing theory w as a product of his observatio n that classical contingencies were em bedd ed in th e discrim inated operan t avo idan ce parad igm . In such situatio ns, he noted ``. . . that co nditioning of th e visceral-vascular, or `diffuse,’ responses takes place ® rst an d that the accom pany ing em otio nal state provides the m otivation, or p roblem , w hich produces the subseq uently observed skeletal, or `precise, ad ap tive,’ reactions’ ’ (p. 127). T herefore, the tem p oral dynam ics of this situ atio n would create stimuli that becam e m otivational m ediators (th rough the classical contingenc y between the w ar ning stimulus an d the shock) as w ell as discriminative in nature (through the operan t co ntingenc y b etween a respo nse an d the ter m ination of the w ar ning stimulus or shock). T hat b etter avo idan ce co nditioning w as obtained if the avo idan ce response imm ediately ter m inated th e w ar ning stimulus than w hen the w ar ning stimulus w as of a ® xed duration clearly supported this position (M ow rer & L am oreou x, 1942). Trapold an d O verm ier (1972) schem atically re presented this ``em b eddedness’ ’ w ith the R S± R± S no tation, an d Rescorla an d S olom o n (1967) b rought the data ger m an e to twofactor lear ning theory together in a powerfu l supporting treatise. Fo llow ing scienti® c practice, m ost two-process lear ning theory research separated the two processes M ow rer identi® ed w ithin th e discriminated operan t situation for an alysis. T hen, after b eing sep arately conditioned, these processes w ere ``synthesized’ ’ . T his w as accom plished w ith the tr an sfer-of-co ntrol parad igm w here a n on-discrim in ated free-operan t co nd itioning phase is followed by a distinct an d separate classical co nditioning ph ase. T hen, in the test phase, the C S (s) are presented to the subject w hile it is eng aged o n the oper an t baseline. T he direction of chan ge in operan t rate du ring the C S, relative to ``truly ran dom controls’ ’ , is used to infer the m otivational proper ties co nditioned to the C S,


377

ex citatory or inhibitory, w ith respect to the reinforcem ent system related to the operan t. M uch of the eviden ce relevan t to ap petitive± aversive interaction theory has b een derived from such tran sfer-of-control designs (D ickinson & Pearce, 1977). T he present investigation of two-process lear ning th eory an d ap petitive± aversive interactions has retur ned to the source o f M ow rer’ s for m ulation, th e classical contingencies em bedded in the discrim inativ e operan t baseline. A s an alter native to the process of separation/synthesis ap p roach described above, in the p resent experiment both processes were studied as they occur naturally w hen stimulus control develops in th e operan t lear ning situatio n. To this end, operan t baselines were created w herein the necessary D ex citatory an d inhib itory properties w ere acq uired by the S s solely throu gh the reinforcem ent differences b etween com po nents of the four-com po nent m ultiple trainin g schedules. Weiss an d his associates have investigated the in¯ u ence of the excitatory an d inhibitory incentive-m otive properties of stimuli acquired directly through im plicit classical contingencies em bedd ed w ith in the operan t training baselines on a variety of behavioural phenom ena. T hese included ad ditive sum m ation (E m urian & Weiss, 1972; Weiss, 1971, 1976 , 1977; Weiss & Van O st, 19 74), generalization peak shift (Weiss & D acany, 1982), ap petitive± aversive interactio ns (current study; Weiss & S ch indler, 1989), an d selective associations (Pan lilio & Weiss, 1993; Weiss, Pan lilio, & Schin dler, 1993a, 1993b). In the p resent experiment, predictions from ap petitive± aversive interaction theory were con® r m ed w hen the resp onse discrim in ative an d incentive properties acquired by D the S s w ere taken into account (Weiss, 1978). T he potential of co m petin g peripheral oper an ts contam inating the resu lts w as directly confronted by having this factor com p arably in¯ uence each of the incentive g roup s in Tests 1 an d 2. T herefore, g roup d ifferences co uld b e directly attributed to the incen tive m an ipulatio n. In Test 1, the stimulus that b ecam e excitatory alw ays occasioned operan t respo nding, w hereas the stimulus that b ecam e inhibitory alw ays occasioned resp onse cessation. In that situation, com pounding an inhibitor w ith an excitor from the sam e incentive class reduced resp onding signi® can tly m ore th an did com pounding an inh ib itor w ith an excitor from the other incentive class. In Test 2, all stimuli occasioned operan t responding. In that situation, com pou nding stimuli that w ere excitors fro m differen t incentive classes ap peare d to create reciprocal inhibition that cou nteracted the ad ditive effects produced w hen these stimuli were excitors from the sam e incentive class. T he con ® r m ations of ap petitive± aversive interactio n theory w ithin this solely operan t b aseline design brings us full circle, back hom e to the parad igm s that inspired two-factor lear ning theory.

R E FE R E N C E S Bacon , W.E., & B indra, D. (19 67). Th e gen erality of th e incentive -motivatio nal effects of clas sically con dition ed stimuli o n instrumental lear ning. Acta B iologia e Experimenta lis, 27, 185± 18 7. Brady, J. (1951) . T he effect of electro-c onvulsive shock on a con dition ed emotion al respo nse: T he per man ence of th e effec t. J ourna l of Compa ra tive & P hysiologica l P sychology, 45 , 9± 13.

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Reber g, D., & B lack, A.P. (1969). Com pou nd tes ting of individ ually con dition ed stimuli as an index of exc itatory an d inhibitor y properties. P sychonomic S cience, 17, 30± 31. Rescorla, R.A. (196 9). Pavlovia n con dition ed inhibitio n. P sychologica l B ulletin, 72 , 77 ± 94. Rescorla, R .A., & L oL ordo, V.M . (196 5). Pavlovia n inhibition of avoid an ce behavio r. J ourna l of Compa ra tive a nd P hysiologica l P sychology, 59, 406± 41 2. Rescorla, R.A ., & S olom o n, R.L . (1967) . Tw o-proc ess lear ning th eory: Relation betw ee n Pavlovian con dition ing an d instrum ental lear ning. P sychologica l R eview, 74, 151± 182. Rescorla, R.A., & Wagner, A.R. (1972). A th eo ry of Pavlovia n con dition ing: Variation s on the effec tiveness of reinfor cement an d non -reinforcem ent. In A.H . Blac k & W. Prokasy (E ds.), Cla ssica l conditioning I I (p p. 64± 99). N ew York: Appleton -Centu ry-Crofts. Szw ejkow ska, G., & K on orski, J. (1959). T he in¯ uence of th e prim ary inhibitory stimulus upon the salivar y effect of exc itatory co ndition ed stimulus. Acta B iologia e Experimenta lis, 19, 16 2± 164. Trap old , M .A., & O ve rmier, J.B. (1972). T he seco nd lear ning process in instrumental lear ning. In A.H. Black & W. Prokasy (E ds.), Cla ssica l conditioning I I (p p. 427 ± 452). N ew York: Appleto n-Cen tu ryCrofts. Wagn er, A.R., & Rescor la, R.A. (197 2). Inhibition in Pavlovi an co ndition ing: Applicatio n of a th eory. In R.A. B oakes & M .S. Hallid ay (E ds.), I nhibition a nd lea rning (pp. 301± 33 6). L ond o n: Acad emic P ress. Weiss, S.J. (1970). An effective an d econ om ical sound atte nuation cham b er. J ourna l of the Experimenta l Ana lysis of B eha vior, 13, 151 ± 155. Weiss, S.J. (197 1). Discrim ination train ing an d stimulus com pou nding: Co nsideration of non reinforceD ment an d respon se cessation con sequence s of S . J ourna l of the Experimenta l Ana lysis of B eha vior, 15, 387± 402. Weiss, S.J. (1976). S timulus con trol of free op erant avoid an ce : T he con tribu tio n of respon se rate an d incentive relations betwe en multiple schedule com po nents. Lea rning a nd Motiva tion, 7, 477± 516. Weiss, S.J. (1977 ). Th e isolatio n of stimulus± rein for cer association s established with multiple schedules. Anima l Lea rning & B eha vior, 5, 421± 429. Weiss, S.J. (1978) . D iscriminate d respon se an d incentive processes in oper an t cond ition ing: A tw o-factor mod el of stimulus co ntrol. J ourna l of the Experimenta l Ana lysis of B eha vior, 30, 361± 38 1. Weiss, S.J., & Dac any, R.J. (1982) . Incentive processes an d th e peak shift. J ourna l of the Experimenta l Ana lysis of B eha vior, 37, 441 ± 453. Weiss, S.J., P an lilio, L .V., & S chindler, C.W. (199 3a). S elective assoc iatio ns produced solely with ap petitive con tin ge ncies: Th e stimulus± reinfor cer interaction revisited. J ourna l of the Experimenta l Ana lysis of B eha vior, 59, 309 ± 322. Weiss, S.J., Pan lilio, L .V., & S chindler, C.W. (199 3b ). Single- incentive selective association s produced solely as a fu nction of com pou nd-stimulus con dition ing con text. J ourna l of Experimenta l P sychology: Anima l B eha vior P rocesses, 19 , 284± 294. Weiss, S.J., & S chindler, C.W. (198 5). C on ditio ning histo ry an d in hibito ry instru m ental stimulus con trol. Anima l Lea rning & B eha vior, 13, 433± 44 6. Weiss, S.J., & Sch indler, C.W. (19 89). Integ ratin g co ntrol gen erated by pos itive an d neg ative reinforcement: Appetitive -aver sive inter actio ns. Anima l Lea rning & B eha vior, 17, 433± 446. Weiss, S.J., & Van O st, S. (1974) . Respo nse discrim inative and reinfor cem ent factor s in th e stimulus con trol of perfor m an ce on multiple an d chained schedules of pos itive reinfor cement. Lea rning a nd Motiva tion, 5, 45 9± 472. Weism an , R.G., & L itn er, J.S. (196 9). Positive co nditio ned reinforcement of Sidm an avoid an ce beh avior in rats. J ourna l of Compa ra tive a nd P hysiologica l P sychology, 68, 597 ± 603.

M a nuscript receiv ed 23 October 1995 Accepted revision received 14 Ma y 1996

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C o m binaison d’e xcitateu rs et d ’in hibiteurs con dition n eÂ s deÂ riveÂ s d’un e lign e de base o peÂ ran te et ap parten ant aÁ un e m eÃ m e classe d ’in citatifs o u aÁ de s classe s d’incita tifs diffeÂ ren tes: U n e exp lo ratio n d es in te ractio n s ap p eÂ titif± aversif L a dy na m iqu e d e la th eÂ orie d es intera ction s ap p eÂ titif± aver sif a eÂ teÂ exam ineÂ e d an s u n e exp eÂ rien ce ouÁ d es exc itateur s et d es inh ibiteu r s ap p arten ant ou n ’ ap pa rtena nt p as aÁ la m eÃ m e classe d’ incitatifs o nt eÂ teÂ asso cieÂ s. L es p ro p rieÂ teÂ s incitatives excitatrice et inh ibitrice acquises p ar les stim uli discrim inatifs p rov en aient d u ren forcem en t diffeÂ rencieÂ d es qu atre com po san ts d e p ro g ram m es d’ en traõÃ n em ent m u ltiples, ouÁ l’ in¯ u en ce d e reÂ p on ses peÂ rip h eÂ riqu es en com p eÂ titio n eÂ tait incluse da ns le sch eÂ m a exp eÂ rim en tal. L’ ap p u i su r le levier p ou r l’ obten tio n d e n our riture ou d an s u n p ro gr am m e d’ eÂ vitem en t ``fre e op eran t’ ’ a per sisteÂ ch ez le r at en p reÂ sen ce d ’ un so n ou d ’ u n clic, alors que l’ extinction avait eÂ teÂ pro g ram m eÂ e en p reÂ sen ce d e la lum ieÁ re ass ocieÂ e au clic, et au ssi en l’ absen ce sim ultaneÂ e d u so n , d u clic et d e la lum ieÁ re. L e p rem ier test a asso cieÂ u n incitateur caus an t la reÂ p on se oper an te et u n inh ibiteu r qu i la s up p rim ait. A sso cier un inh ibiteu r et u n excitateu r ap par tenan t aÁ la m eÃ m e classe d ’ incitatifs reÂ d u it les reÂ p on ses sign i® cativem en t p lus qu e n e le fait l’as sociation d ’ u n inh ibiteu r et d’ u n excitateu r ap p ar ten an t aÁ u n e au tre classe d’ incitatifs. D an s le secon d test, tou s les stim uli ind ividu ellem en t asso cieÂ s co ntroÃ laien t la reÂ po nse op era nte. D an s ce cas, la com binaison de stim uli e xcitateu r s ap p arten ant aÁ d es classes d’ incitatifs d iffeÂ rentes a pro d u it u n e inh ib ition reÂ cipro qu e qu i a co ntre car reÂ les effets add itifs obten us lorsqu e ces stim u li so n t d es excitateur s app ar tenan t aÁ la m eÃ m e classe d ’ incitatifs. L es preÂ d iction s d e la th eÂ orie d es inter action s app eÂ tif-aversif et d u m od eÁ le d e co n troÃ le d u stim ulu s aÁ d eu x facte ur s d e Weiss o n t eÂ teÂ co n ® r m eÂ es p ar c e p lan exp eÂ rim en tal ouÁ tou s les con ditio n n em ents eÂ taient u n so u s-pro d u it d es com p ortem en ts p ro gra m m eÂ s d an s les lign es de base op eÂ r an tes.

Efectos d e la com b in acioÂ n d e ex citado res e in hibido res con dicion ad os d e d iferen tes cla se s d e incen tivo y ge nerad os a partir d e lõÂ n eas de b ase d e con d ucta o p era nte: U n a in vestig acioÂ n so bre la s in te raccio n es ape titivo ± aversivo E n u n experim en to en el qu e se com binaro n estõÂ m u los excitatorios e inh ibitorios d e la m ism a oÂ d iferen te clase d e incen tivo se an alizoÂ la din aÂ m ica de la interac cioÂ n ap etitivo± avers ivo. L as pro p ied ad es excitatorias e inh ibitorias d e incen tivo ad qu iridas p or los estõÂ m ulos discrim inativos fu ero n resu ltado d e las d iferen cias d e reforzam iento en tr e los com po nen tes de p ro g ram as d e entre n am ien to m uÂ ltiples co n cuatro com p on en tes, incluyeÂ n d ose c om o factor en el d isenÄ o la in¯ u en cia d e las re sp u estas p erifeÂ ricas com p etidoras. L a resp u esta d e p resioÂ n de p alanca d e u n as ra tas fu e m anten ida en p resenc ia d e u n ton o oÂ d e u n clic m edian te re fu erzo alim en ticio o evitacioÂ n d e u n sh ock p or op eran te libre, m ien tras qu e en p resen cia de clic m as luz o e n au se ncia co n jun ta d e ton o, clic y luz, se p ro gr am oÂ la extinc ioÂ n . E n la Pr u eba 1, se p resen taro n al m ism o tiem p o un exc itador qu e gener aba co n du cta op er an te y u n inh ibidor qu e la h acõÂ a cesar. E n este caso, la com binacioÂ n d e u n excitador y u n inh ibidor d e la m ism a clase d e incen tivo red ujo la con du cta s ign i® cativam en te m aÂ s qu e la com binacioÂ n d e u n inh ibidor con u n excitado r d e la otr a c lase d e incen tivo. E n la P ru eba 2, tod os los estõÂ m ulos com binad os ind ividu alm en te gen erar on con d u cta oper an te. E n este caso, la com binacioÂ n d e


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estõÂ m ulos excitatorios d e d istintas clases d e incen tivo p rob ablem en te d io lug ar a u n a inh ibicioÂ n recõÂ pro ca qu e co n tr ar res toÂ los efectos ad itivos pr od u cidos cu an d o los estõÂ m ulos eran excitador es d e la m ism a clase. L as p red iccio ne s de la teorõÂ a de la inter accioÂ n ap etitivo± ave rsiv o y d el m od elo bifactorial d e Weiss so bre el co ntro l de estõÂ m ulos fu ero n co n® r m ad as en este d isenÄ o exp erim en tal, en el que el con d icion am ien to er a con secu encia d e las con tingencias con d uctu ales p ro gr am ad as en las lõÂ ne as d e base op eran tes.