On day 1 o f stage 1 in Experiment 9, Group N showed g re a t suppression to the li g h t . However, in th is experim ent, th e re was no sig n o f th is (see F ig u re 10); so i t cannot be a r e lia b le phenomenon.
W ith magazine e n trie s (F ig u re 11), Group P appears to increase th e ra te o f e n try more than Group N, d u rin g both th e tone and the
li g h t . However the e ffe c t o f Groups f e l l s h o rt o f s ig n ific a n c e d u rin g ^ th e tone (F=3.8, d f= 1 ,l4 , p<0.08), and d u rin g th e li g h t (F=2.9,
d f= 1 ,1 4 , p> 0 .1 ). A ll o th e r F 's le s s than 1 .3 , except the e ffe c t o f Days d u rin g th e l i g h t (F=3.7, df=8,112, p<0.001), presumably due to a s lig h t decrease in the suppression r a t io ( ie , le s s a c c e le ra tio n ) over days, e s p e c ia lly in Group N. Comparing F igures 10 and 11, we can see th a t u sin g magazine e n trie s so lve s the problem o f a f lo o r e ffe c t. W ith le v e r p re ssin g , th e li g h t produces suppression r a tio s o f around
0 .3 ; but w ith magazine e n trie s , the r a tio s are 0 .5 -0 .7 * , i U n fo rtu n a te ly , w ith magazine e n trie s , Group P appears to have a la rg e r
r a t io than Group N. ^
The c r i t i c a l data were f o r th e lig h t-s h o c k t r i a l s , and these are ; } shown in F igures 12 and 13. There is g re a te r suppression in Group N .{ a t th e s ta r t o f stage 2, and both groups ra p id ly approach complete ! suppression, both w ith le v e r presses (F igu re 12), and w ith magazine i e n trie s (F ig u re 13), as th e response measure. A n a lysis o f th e le v e r ’ press data revealed a la rg e e ffe c t o f T r ia ls (F=6.7, d f= 5 ,6 0 , ^ p<0.001), and no e ffe c t o f Groups (F<1); the Group * T r ia ls ‘ In te ra c tio n f e l l sh o rt o f s ig n ific a n c e (F=1.8, d f= 5 ,6 0 , p> 0.05). /j Whereas, th e da ta using magazine e n trie s , produced a s ig n ific a n t j e ffe c t o f Groups (F=7.1, d f ^ l ,1 4 , p<0.05), as w e ll as th e la rg e e ffe c t
was n o t s ig n ific a n t (F=2.0, d f= 5 ,5 6 , p>0.05). As th e mean suppression f o r both groups on both response measures converges around zero on the la s t 3 t r i a l s , i t is e v id e n t th a t th e Group e ffe c t is due to group d iffe re n c e s on the f i r s t 3 t r i a l s ; ie . Group N was i n i t i a l l y more suppressed. As was discussed above, i t appeared th a t d u rin g stage 1, Group N’ s suppression r a tio s f o r th e magazine e n trie s d u rin g th e li g h t were approaching 0 .5 , b u t Group P 's were rem aining around 0 .7 . Although the reason f o r th is is u n c le a r, th is o b se rva tio n accounts f o r th e re s u lts obtained f o r th e lig h t-s h o c k t r i a l s .
In stage 2, th e pre-CS le v e r press ra te s were 14.2 presses per min fo r Group P, and 14.9 f o r Group N; these fig u re s were n o t r e lia b ly d iffe r e n t (F<1). D uring tone-shock t r i a l s (stage 3 ), the pre-CS ra te s were 23.5 pre sses/m in f o r Group P, and 16.2 f o r Group N. D e spite the la rg e num erical d iffe re n c e , th e re was no s t a t is t ic a l d iffe re n c e (F=1.8, d f= 1 ,l4 , p > 0 .1 ), and th e num erical d iffe re n c e was due to 2 r a ts in Group P having h ig h pre-CS ra te s (50 and 39 p re sse s/m in ).
The tone-shock t r i a l s (stage 3, see F ig u re 12 and 13) appear to shew a la rg e and m aintained se p a ra tio n between th e 2 groups: Group P being more suppressed on a l l 4 t r i a l s , and both response measures, than Group N. T his was v e r ifie d s t a t is t ic a lly . For le v e r presses, th e re were la rg e and s ig n ific a n t e ffe c ts o f Group (F=22, d f= 1 ,l4 , p<0.0005) and T r ia l (F=7.4, d f= 3 ,4 l, p<0.001). There was no in te r a c tio n (F<1). L ike w ise , th e data fo r magazine e n trie s gave s ig n ific a n t e ffe c ts o f Group (F=21, d fa 1 ,13, p<0.001) and T r ia l
(F=5.2, d f= 3,3 8, p< 0.01), and no in te r a c tio n . Thus these tone-shock t r i a l s have given us good evidence th a t Group P was more a fra id in the presence o f th e to ne. T his must be due to the p revio us lig h t-s h o c k
o 0.7
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