Perfil de Ingreso:

There was no sig n o f any group d iffe re n c e in a c q u is itio n o f the tone— >shock a s s o c ia tio n . The o n ly problem w ith acce p tin g the n u ll h yp o th e sis, is the poor le v e l o f c o n d itio n in g . However, th e next experim ents lo o k f o r shock a s s o c ia b ility changes w h ile em ploying a

d iffe r e n t procedure. j

EXPERIMENT 5

Experiment 4 employed ju s t one s u rp ris in g double shock episode, in an attem pt to increase the shock's a s s o c ia b ility . This is s im ila r to H a ll and P earce's (1982) approach o f using ju s t 2 tone o n ly t r i a l s , to increase the to n e 's a s s o c ia b ility . In th is experim ent, an

a lte rn a tiv e s tra te g y is used; one group is g ive n many t r i a l s in w hich I

the shock is w e ll p re d ic te d , and another group is given many t r i a l s in

which the shook is p o o rly p re d ic te d . According to a M ackintosh-type ^

"1

argum ent, th e w e ll p re d ic te d shock w i l l have h ig h e r a s s o c ia b ility than

th e p o o rly p re d icte d one; b u t a P e a rce -H a ll-typ e a n a ly s is in d ic a te s :>| the o p p o s ite .

The design fo r th is experim ent is shown in Table 9 *. A ll ra ts

were given prolonged stage 1 tr a in in g . W ith the p re d ic tiv e r e la tio n [ - ^ (Group P ), th e shook always fo llo w e d one o f the two li g h t s tim u li, and | never came a fte r th e o th e r s tim u lu s . W ith the n o n -p re d ic tiv e r e la tio n

4

TABLE 9: DESIGN OF EXPERIMENT 5

Stage 1 Stage 2

(52 t r i a l s ) (8 t r i a l s )

Group. P .. L I —^Sh, L2 T—^Sfa

Group N L I —)Sb—+, L2—^Sh—+ T—^Sh

Key: L I = 1 st l i ^ t stim u lu s , L2 = 2nd lig h t stim u lu s , T = tone

Sh = shook, -+ = shook occurs on h a lf the t r i a l s . ^

. (Group. N) a shock fo llc w e d both lig h t s tim u li on e x a c tly 50$ o f t r i a l s . So, s u b je c ts in Group P would know when shocks were coming (a t the onset o f a lig h t s tim u lu s ), b u t Group N would not knew. Then stage 2 in v e s tig a te s th e p o s s ib ility o f a d iffe re n c e in shock a s s o c ia b ility f o r the two groups, as evinced by c o n d itio n in g to a tone CS.

Method

S u b je cts: . 16 e x p e rim e n ta lly naive r a ts were used and were s in g ly housed, in th e Psychology Department o f S t Andrews U n iv e r s ity , a f te r being bought from OLAC ( 1976) L td . The s u b je c ts weighed between 276 and 313 grams (mean 296 g ) a t th e s t a r t o f the experim ent; th e y were

subsequently m aintained a t 85$ o f t h e ir fre e -fe e d in g w e ig h t, by g iv in g them th e necessary amount o f food a fte r each d a ily session. The i n i t i a l ta rg e t w e igh t was increased by one gram each day.

Apparatus; As Experim ent 2.

Procedure; A fte r tr a in in g th e s u b je c ts to le v e r press fo r fo od, a l l d a ily sessions la s te d 60 m inutes and in vo lve d a V I 60 schedule. A fte r 3 days o f b a se lin e tr a in in g , th e re were 2 days w ith 2 tone alone p re se n ta tio n s per day ( in th e 16th and 36th m in u te s ). The s u b je c ts were then assigned to groups by m atching f o r suppression on th e f i r s t tone p re s e n ta tio n . There was then one day w ith 4 L I a lone, and 4 L2 o n ly p re s e n ta tio n s . For h a lf the r a ts in each group, L I was th e fla s h in g h o u s e lig h t, and L2 was the panel lig h t s (v ic e versa f o r the o th e r r a ts ) . The fla s h in g h o u s e lig h t was on f o r 100 msec and o f f f o r 100 msec; and the panel lig h t s consiste d o f the ce n tre and l e f t panel lig h t s fla s h in g on f o r 2 sec, and o f f f o r 200 msec. As b e fo re , the s tim u li were on f o r 60 seconds per p re s e n ta tio n . Then th e re were 13 f u r th e r days w ith 4 L I and 4 L2 p re s e n ta tio n s ; f o r Group P, th e L I t r i a l s were always im m ediately fo llo w e d by a 0.4 mA, 0.5 sec shock, and th e L2 t r i a l s were n o t; f o r Group N, 2 L I and 2 L2 p re se n ta tio n s were fo llo w e d by th e shock, the o th e r t r i a l s were n o t fo llo w e d by th e shock. The two groups were balanced across boxes, and f o r th e o rd e r in w hich th e ir d a ily sessions were ru n .

The in te r v a l between th e onset o f a lig h t p re s e n ta tio n and the onset o f the n e xt li g h t p re s e n ta tio n v a rie d in th e fo llo w in g sequence? 4 ,8 ,6 ,7 ,5 ,8 ,9 and 5 m in. The i n i t i a l tim e delay was ro ta te d between days, b u t the o rd e r o f the sequence was n o t ( ie , day Is 4 ,8 , 6 .. , day

2s 8 ,6 ,7 .., e tc ) . The f i r s t l i g h t p re s e n ta tio n per session occurred a f te r 2 min p lu s w hatever th e sequence d ic ta te d , so th a t th e la s t p re s e n ta tio n always occurred a fte r the 54th m inute.

The o rd e r o f t r i a l s was v a rie d between days, b u t su b je c t to th e c o n s tra in t th a t a l l 4 p o s s ib le t r i a l s f o r Group N (L1-->Sh, L2— >Sh, L 1 -, L 2 -) occurred once in th e f i r s t 4 t r i a l s and once in th e second 4

t r i a l s . The 2 groups re ce ive d the shocks a t the same tim e (a lth o u g h th e preceding l i g h t was o fte n d iff e r e n t ) .

Then th e re were two stage 2 te s t days, w ith the tone CS im m ediately fo llo w e d by th e shock fo u r tim es on both days.