DURATIONS OF ACOUSTIC SEGMENTS UNDER SYNCHRONOUS AND DELAYED FEEDBACK CONDITIONS by Ingrid Jeffrey B . A . , Simon Fraser Un ive r s i t y , 1972 . A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n the Department of Paediatr ics D i v i s i o n of Audiology and Speech Sciences We accept th i s thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA July,1974 In p resent ing t h i s t h e s i s in p a r t i a l f u l f i l m e n t o f the requirements f o r an advanced degree at the U n i v e r s i t y of B r i t i s h Columbia, I agree that the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e fo r reference and study. I f u r t h e r agree tha t permiss ion fo r e x t e n s i v e copying of t h i s t h e s i s fo r s c h o l a r l y purposes may be granted by the Head of my Department or by h i s r e p r e s e n t a t i v e s . It i s understood that copying or p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l ga in s h a l l not be a l lowed without my w r i t t e n p e r m i s s i o n . Department of PCLICLL CLI^LCS The U n i v e r s i t y of B r i t i s h Columbia Vancouver 8. Canada Date Qdoltr 9* /?7 V T D ( I ) R L ( K ) ~ SD(I) A TD (k) where, f o r a p a r t i c u l a r segment, RC(k) i s the r e l a t i v e i n -crease or decrease i n d u r a t i o n of an a c o u s t i c segment i n a p a r t i c u l a r c o n d i t i o n k ( I I , I I I , or IV) w i t h r e s p e c t t o the corresponding segment i n the NORMAL c o n d i t i o n , SD(k) i s the d u r a t i o n of the a c o u s t i c segment under c o n d i t i o n k, and TD(k) i s the ' t o t a l d u r a t i o n ' under c o n d i t i o n k. T h i s measure r e f l e c t s the r e l a t i v e i n c r e a s e o r decrease i n dura-t i o n of an a c o u s t i c segment compared to i t s d u r a t i o n i n the NORMAL c o n d i t i o n and normalized w i t h r e s p e c t t o the two c o r -responding ' t o t a l d u r a t i o n s ' . An RC value of 1.0 c o r r e s -ponds to no change, an RC val u e g r e a t e r than 1.0 corresponds to a r e l a t i v e i n c r e a s e and an RC value l e s s than 1.0 c o r r e s -ponds to a r e l a t i v e decrease. 'Increase' or 'decrease' w i l l be used h e r e a f t e r to r e f e r to the r e l a t i v e i n c r e a s e or de-crease c a l c u l a t e d by means of the above formula. The RC value s obtained from the a n a l y s i s of the four main experiment sentences w i l l be r e p o r t e d f o r d i f -f e r e n t s e t s o f phones s e p a r a t e l y . Any l e v e l s of s i g n i f i c a n c e mentioned i n t h i s study w i l l r e f e r to l e v e l s of s i g n i f i c a n c e e s t a b l i s h e d by t - t e s t s as f o l l o w s : * = s i g n i f i c a n t beyond the 0.05% l e v e l ** = s i g n i f i c a n t beyond the 0.02% l e v e l *** = s i g n i f i c a n t beyond the 0.01% l e v e l **** = s i g n i f i c a n t beyond the 0.005% l e v e l - 68 -6•3 R e l a t i v e Change o f V o w e l s I t became n e c e s s a r y i n the c o u r s e o f a n a l y s i s , on t h e b a s i s o f t h e i r a p p a r e n t l y d i f f e r e n t f u n c t i o n s , t o c o n -s i d e r v o w e l s i n m o n o s y l l a b i c f u n c t i o n words such as p r e p o -s i t i o n s , p r o n o u n s , and d e t e r m i n e r s , s e p a r a t e l y f rom the v o w e l s i n o t h e r w o r d s , p r i m a r i l y words b e a r i n g l e x i c a l i n -f o r m a t i o n . H e r e a f t e r ' s t r e s s e d ' v o w e l w i l l r e f e r t o v o w e l s i n s t r e s s e d s y l l a b l e s i n words o t h e r t h a n t h e m o n o s y l l a b i c f u n c t i o n w o r d s , and ' u n s t r e s s e d ' v o w e l w i l l r e f e r t o v o w e l s i n a l l o t h e r s y l l a b l e s . ' U n s t r e s s e d ' l o n g and s h o r t and ' s t r e s s e d ' l o n g and s h o r t v o w e l s were a n a l y z e d s e p a r a t e l y . F i g u r e 6.4 d i s p l a y s the r e l a t i v e change f o r t h e d i f f e r e n t g roups o f v o w e l s f o r each s u b j e c t . As can be s e e n , t h e v o w e l s i n t h e f u n c t i o n words ' i n c r e a s e d ' more t h a n any o t h e r g roup o f v o w e l s . T a b l e I I shows t h e b e t w e e n - c o n d i t i o n s t a t i s t i c a l d i f f e r e n c e s f o r v o w e l s i n f u n c t i o n words and t a b l e I I I shows t h e w i t h i n - c o n d i t i o n s t a t i s t i c a l d i f f e r e n c e s . The ' i n c r e a s e s ' f o r v o w e l s i n f u n c t i o n words i n the SLOW SAF c o n d i t i o n were s i g n i f i c a n t l y d i f f e r e n t f rom the ' i n -c r e a s e s ' i n t h e FAST DAF c o n d i t i o n and t o a l e s s e r e x t e n t f rom the ' i n c r e a s e s ' i n t h e SLOW DAF c o n d i t i o n . F u r t h e r -more , t he ' i n c r e a s e s ' f o r t he v o w e l s / u / , / o / , and / a / i n f u n c t i o n words were f r e q u e n t l y s i g n i f i c a n t l y d i f f e r e n t f rom t h e ' i n c r e a s e s ' f o r / i i / , /'6/ and ' s t r e s s e d ' v o w e l s r e s p e c t -i v e l y . Mos t o f t h e s i g n i f i c a n t d i f f e r e n c e s o c c u r r e d i n the SLOW c o n d i t i o n s . The r e l a t i v e changes f o r t h e v o w e l s /A/ and /ae/ i n f u n c t i o n words were r a r e l y s i g n i f i c a n t l y S t r e s s e d ' v o w e l s o 3.5 -3 — 2.5 -2 — i u 1.5 -I-o 0.5 -3.5 -3 — 2.5 -2 — 1.5 -I — 0.5 -3.5 -3 — a 2.5 -_K33 O 2 — 1.5 -I - m=f^ 0.5 A 6 u[ e I ] u* A' 6 6[e\] ' U n s t r e s s e d ' v o w e l s 1 I U A O u [ a l ] r it CL V o w e l s i n m CONDITION n u n c t i o n words 8 CONDITION ISC F i g u r e 6 . 4 . R e l a t i v e change i n d u r a t i o p . f o r vowe l s i n the and the FAST DAF (IV) c o n d i t i o n s w i t h r e s p e c t t o I I CONDITION ur l i p SUBJECT I ae u SUBJECT 2 SUBJECT 3 SLOW SAF ( I I ) , the SLOW DAF ( I I I ) , t he NORMAL c o n d i t i o n . - 70 -SLOW DAF FAST DAF S u b j e c t 1 NS ** SLOW SAF 2 * **** 3 ** **** T a b l e I I . B e t w e e n - c o n d i t i o n d i f f e r e n c e s i n r e l a t i v e change o f v o w e l s i n o n e - s y l l a b l e f u n c t i o n w o r d s . - 71 -SLOW SAF SLOW DAF FAST DAF / i i / v s . / u / i n f u n c t i o n w o r d s , / u / s e n t e n c e S u b j e c t 1 * **** NS 2 ** ** **** * * 3 *** NS * * * /6/ v s . /o/ i n f u n c t i o n w o r d s , / o / s e n t e n c e S u b j e c t 1 NS *** NS 2 * * * * **** **** 3 * NS NS / a / v s . /A/ and / a / i n f u n c t i o n w o r d s , / a / s e n t e n c e S u b j e c t 1 * * * "k NS NS 2 NS * NS 3 NS NS NS ' s t r e s s e d ' v o w e l s v s . / e / i n f u n c t i o n w o r d s , a l l s e n t e n c e s S u b j e c t 1 **** **** **** 2 **** **** ]vjg 3 **** **** ftjg T a b l e I I I . W i t h i n - c o n d i t i o n d i f f e r e n c e s i n r e l a t i v e change o f ' s t r e s s e d ' l o n g v o w e l s and v o w e l s i n f u n c -t i o n w o r d s . 72 -d i f f e r e n t from the r e l a t i v e changes f o r the vowel /a/. The s m a l l number of occurrences of /A/ and / f f i/ (N=3) might account f o r the n o n s i g n i f i c a n t r e s u l t s f o r these vowels. However, an a l t e r n a t i v e e x p l a n a t i o n w i l l be o f f e r e d below, when these r e s u l t s are d i s c u s s e d . In order to assure t h a t the d i f f e r e n c e between ' s t r e s s e d ' vowels and /a/ i n f u n c t i o n words was not simply due to the d i f f e r e n c e s i n vowel q u a l i t y , /%/ i n words other than f u n c t i o n words, e.g., i n / s i t e d / , were compared with ' s t r e s s e d ' vowels. The s t a t i s t i c a l r e -s u l t s , presented i n t a b l e IV, i n d i c a t e t h a t there i s r a r e l y a s i g n i f i c a n t d i f f e r e n c e i n r e l a t i v e change between / s / i n words other than f u n c t i o n words and ' s t r e s s e d ' vowels. A l l e n (1968) i n a d i s c u s s i o n of rhythmic behaviour i n motor ta s k s proposed t h a t the minimum i n t e r v a l between a c t s f o r rhythmic behaviour i n speech (beats) i s probably 300 msec and the maximum i n t e r v a l 1000 msec. I t was found i n the presen t study t h a t when the vowels i n f u n c t i o n words are examined, the speech power t r a c e on the mingograms i s as hi g h f o r these vowels as f o r the vowels which have heen c a l l e d ' s t r e s s e d ' vowels i n t h i s study. When the data are examined i n view of A l l e n ' s minimum and maximum l i m i t s , i t becomes e v i d e n t , t h a t the s u b j e c t s , at the slower r a t e s of speech and p a r t i c u l a r l y a t the very slow r a t e i n the SLOW SAF and SLOW DAF c o n d i t i o n s , lengthened vowels and i n c r e a s -ed the p h y s i c a l e f f o r t with which they were produced i n comparison w i t h the NORMAL c o n d i t i o n such, t h a t each vowel became a beat i n the rhythmic s u c c e s s i o n of speech - 73 -SLOW SAF SLOW DAF FAST DAF ' S t r e s s e d ' v o w e l s v s . / 9 / n o t i n f u n c t i o n words S u b j e c t 1 NS NS NS 2 NS *** NS 3 ** * * T a b l e I V . W i t h i n - c o n d i t i o n d i f f e r e n c e s i n r e l a t i v e change o f ' s t r e s s e d ' v o w e l s and / a / n o t i n f u n c t i o n w o r d s . - 74 -u n i t s . F u r t h e r e x a m i n a t i o n r e v e a l e d t h a t t h e i n t e r v a l s b e -tween t h e n o r m a l l y s t r e s s e d v o w e l s w o u l d have exceeded 1000 msec a t t h e s l o w e r r a t e s o f s p e e c h , t h u s n e c e s s i t a t i n g the a d d i t i o n a l b e a t s . I n o t h e r t e r m s , t h e s l o w e r the r a t e o f s p e e c h , t h e more l i k e l y w i l l a n o r m a l l y u n s t r e s s e d v o w e l be p r o l o n g e d and form a b e a t i n t h e r h y t h m i c s u c c e s s i o n o f speech u n i t s . T h i s may e x p l a i n why t h e d i f f e r e n c e s between t h e SLOW SAF and SLOW DAF c o n d i t i o n s f o r v o w e l s i n f u n c t i o n words were n o t as s i g n i f i c a n t as t he d i f f e r e n c e s between t h e SLOW SAF and FAST DAF c o n d i t i o n and why i n the FAST DAF c o n d i t i o n t h e r e s h o u l d be fewer s i g n i f i c a n t d i f -f e r e n c e s between ' s t r e s s e d ' v o w e l s and v o w e l s i n f u n c t i o n w o r d s . The e x c e p t i o n s , i . e . , t h e v o w e l s i n f u n c t i o n words w h i c h d i d n o t i n c r e a s e s i g n i f i c a n t l y i n d u r a t i o n i n com-p a r i s o n w i t h o t h e r v o w e l s , were now examined i n v i e w o f the above h y p o t h e s i s : i t was found t h a t t h e s e e x c e p t i o n s o c c u r r e d between two b e a t s (two s t r e s s e d v o w e l s ) w h i c h were n o t s e p a r a t e d from each o t h e r by more t h a n 1000 msec . I n a d d i t i o n , t h e s e e x c e p t i o n a l v o w e l s , e . g . , / A / i n / A p / and /ae / i n / a t / , o c c u r r e d i n an e n v i r o n m e n t t h a t i n the NORMAL c o n d i t i o n w o u l d c a l l f o r a s h o r t e r v o w e l . A d i s -c u s s i o n o f t h i s l a t t e r p o i n t f o l l o w s when t h e r e s u l t s o f t h e a n a l y s i s o f ' s t r e s s e d ' v o w e l s a r e d i s c u s s e d . A n a l y s i s o f t h e ' s t r e s s e d ' v o w e l s (see f i g u r e 6 .4) r e v e a l e d t h a t i n g e n e r a l /ix/ was c o n s i s t e n t l y most ' i n -c r e a s e d ' i n t h e SLOW SAF c o n d i t i o n , and more ' i n c r e a s e d ' i n t h e SLOW DAF c o n d i t i o n t h a n i n t h e FAST DAF c o n d i t i o n . - 75 -The r e v e r s e was t r u e f o r /o/, where t h e g r e a t e s t i n c r e a s e o c c u r r e d i n t h e FAST DAF c o n d i t i o n , / u / was more ' i n c r e a s e d ' t h a n any o t h e r ' s t r e s s e d ' v o w e l i n any o t h e r c o n d i t i o n w i t h t h e e x c e p t i o n o f /6/ i n t h e FAST DAF c o n d i t i o n . / u / i n / u e l / was n o t i n c l u d e d i n t h e a n a l y s i s o f / u / b e c a u s e o f t h e c o n s i s t e n t l y d i f f e r e n t b e h a v i o u r o f / u / i n t h i s e n v i r o n -ment. T a b l e V shows t h e w i t h i n - c o n d i t i o n d i f f e r e n c e s i n r e l a t i v e change f o r t h e f o u r g r o u p s o f ' s t r e s s e d ' v o w e l s . As c a n be s e e n , t h e ' i n c r e a s e s ' f o r / u / were s i g n i f i c a n t l y d i f f e r e n t f r o m ' i n c r e a s e s ' f o r t h e low v o w e l s ( p r i m a r i l y /a/) i n t h e SLOW SAF and SLOW DAF c o n d i t i o n s f o r s u b j e c t s 1 and 2. F o r s u b j e c t 3 t h i s d i f f e r e n c e r a r e l y r e a c h e d s i g n i f i c a n c e , a l t h o u g h t h e d i r e c t i o n o f t h e d i f f e r e n c e was t h e same, namely / u / was more ' i n c r e a s e d ' t h a n t h e low v o w e l s . The o n l y s i g n i f i c a n t b e t w e e n - c o n d i t i o n d i f -f e r e n c e s f o r ' s t r e s s e d ' v o w e l s ( n o t shown i n t a b l e form) were as f o l l o w s : w i t h r e s p e c t t o t h e SLOW SAF c o n d i t i o n , the, ' i n c r e a s e s ' f o r /o/ and / i / were e a c h s i g n i f i c a n t l y d i f f e r e n t f o r one s u b j e c t i n t h e FAST DAF c o n d i t i o n and / a / was s i g n i f i c a n t l y d i f f e r e n t f o r one s u b j e c t i n t h e SLOW DAF c o n d i t i o n . A n a l y s i s o f ; t h e v o w e l s i n t h e p a s s a g e s u b s t a n t i a t e d t h e a b o v e f i n d i n g s i n t h a t v o w e l s i n f u n c t i o n words ' i n -c r e a s e d ' more t h a n any o t h e r t y p e o f v o w e l and most a t t h e s l o w e s t r a t e , i . e . , i n t h e SLOW SAF c o n d i t i o n . The a v e r a g e RC v a l u e s f o r v o w e l s i n t h e p a s s a g e amounted t o 1.51 i n t h e SLOW SAF c o n d i t i o n , 1.3 8 i n t h e SLOW DAF - 76 -/ a / /?/ / i / /u/ SLOW SAF Subject 1 / a / 2 Subject 1 /5V 2 NS NS NS NS NS NS NS * NS **** **** NS * * **** NS Subject 1 / i / 2 NS * NS SLOW DAF Subject 1 / a / 2 Subject 1 /6/ 2 NS NS NS NS NS NS NS NS NS **** * * * *** ** * NS Subject 1 / ! / 2 * * NS NS FAST DAF Subject 1 / a / 2 Subject 1 75 / 2 NS NS NS NS * * * NS NS * NS * ** * NS NS NS NS NS Subject 1 / i / 2 NS NS NS Table V. W i t h i n - c o n d i t i o n d i f f e r e n c e s i n r e l a t i v e change of " s t r e s s e d 1 vowels. - 77 -c o n d i t i o n , and 1.2 0 i n the FAST DAF c o n d i t i o n . Why was /u/ more ' i n c r e a s e d ' than the other vowels and p a r t i c u l a r l y more than / a / i n the SLOW c o n d i t i o n s ? Two d i f f e r e n t answers w i l l be examined i n d e t a i l : (a) the vowel /u/ i t s e l f d i f f e r s from the other vowels such t h a t i t e x p l a i n s the g r e a t e r ' i n c r e a s e ' , (b) the environment i n which /u/ o c c u r r e d , d i f f e r e d " f r o m the environment i n which the other vowels o c c u r r e d such, t h a t i t w i l l e x p l a i n the g r e a t e r ' i n c r e a s e ' . (a) The vowel /u/ d i f f e r s , as does / i / , from / a / and /o/ i n t h a t i t has a lower i n t r i n s i c amplitude ( L e h i s t e and Peterson, 1959) and /u/ d i f f e r s from a l l other vowels i n t h a t i t i s c l o s e and back. Why /u/ should behave d i f f e r -e n t l y cannot be e x p l a i n e d i n terms of these f a c t s . (b) House and Fairbanks (1953) found t h a t v o i c i n g , manner and p l a c e of a r t i c u l a t i o n , i n t h a t o r d e r , e x e r t an i n f l u e n c e on vowel d u r a t i o n , e.g., i n v o i c e d environments vowels are g e n e r a l l y longer; when preceded and f o l l o w e d by f r i c a t i v e s , vowels are longer, whereas when preceded and f o l l o w e d by stops, vowels are g e n e r a l l y s h o r t e r ; when pre -ceded and f o l l o w e d by consonants with a b i l a b i a l p l a c e of a r t i c u l a t i o n , vowels are g e n e r a l l y s h o r t e r . A c c o r d i n g to Peterson and L e h i s t e (1960) , the i n f l u e n c e of the preceding consonant on vowel d u r a t i o n i s minimal. Chen (197 0) con-firm e d t h a t the i n c r e a s e i n vowel d u r a t i o n b e f o r e a v o i c e d consonant i s t r u e f o r o t h e r languages as w e l l . D e l a t t r e (1962) suggested t h a t the changes i n vowel d u r a t i o n are - 78 -f o r t h e most p a r t p h y s i o l o g i c a l l y c o n d i t i o n e d , i . e . , " a n t i -c i p a t i o n o f g r e a t e r e f f o r t " ( c l u s t e r s , c l o s u r e s , no v o i c i n g ) "would make one ' s h o r t e n ' t h e v o w e l " ( i b i d . , p. 1 1 4 2 ) . Chen (1970) p r o p o s e d t h a t o b s e r v e d f a s t e r t r a n s i t i o n s f r o m an open v o c a l t r a c t (vowel) t o a more c l o s e p o s i t i o n f o r a v o i c e l e s s c o n s o n a n t e x p l a i n most s a t i s f a c t o r i l y t h e s h o r t e r d u r a t i o n o f a v o w e l b e f o r e a v o i c e l e s s s t o p . When t h e / u / s e n t e n c e i s now compared w i t h t h e o t h e r s e n t e n c e s , i t i s e v i d e n t t h a t / u / a p p e a r e d more f r e q u e n t l y i n an e n v i r o n m e n t w h i c h r e s u l t s i n a s h o r t e r d u r a t i o n o f t h e v o w e l a c c o r d i n g t o t h e above f i n d i n g s . The v o w e l o c c u r r i n g l e a s t f r e q u e n t l y i n s u c h an e n v i r o n m e n t was / a / . Does t h i s i m p l y t h a t , when t h e r a t e o f s p e e c h i s d e c r e a s e d , v o w e l s i n an e n v i r o n m e n t , w h i c h r e s u l t s i n a l o n g e r v o w e l d u r a t i o n , a r e p r o l o n g e d r e l a t i v e l y more t h a n v o w e l s i n an e n v i r o n m e n t w h i c h s h o r t e n s t h e d u r a t i o n o f t h e v o w e l ? I n o t h e r t e r m s , do l o n g e r segments a t s l o w e r r a t e s o f s p e e c h t e n d t o be r e l a t i v e l y more p r o l o n g e d t h a n s h o r t e r segments? The o t h e r f a c t o f i n t e r e s t e m e r g i n g f r o m t h e an-a l y s i s o f ' s t r e s s e d ' v o w e l s was t h e c o n s i s t e n t l y g r e a t e r ' i n c r e a s e ' f o r / $ / i n t h e FAST DAF c o n d i t i o n . I n v i e w o f t h e e a r l i e r r e p o r t e d f i n d i n g s by Sussman and S m i t h (1971) t h a t jaw a c t i v i t y f o r t h e v o w e l s / i / , / e / and /ae/ was l o n g -e s t a t 100-msec d e l a y , i t i s p e r h a p s n o t t o o s u r p r i s i n g t h a t i n t h e p r e s e n t s t u d y , where l o n g e r t h a n 100-msec de-l a y s were u s e d , no c o n s i s t e n t ' i n c r e a s e s ' u n d e r DAF f o r t h e - 79 -v o w e l s / £ / , / u / and / a / were f o u n d . How, t h e n , c a n t h e c o n s i s t e n t ' i n c r e a s e s ' f o r /6/ be e x p l a i n e d ? I s i t p o s -s i b l e , t h a t f o r /6 / a l o n g e r t h a n 100-msec d e l a y i s needed t o p roduce l o n g e s t jaw a c t i v i t y ? Any h y p o t h e s i s w h i c h w o u l d a t t e m p t t o e x p l a i n s e l e c t i v e v o w e l d u r a t i o n under DAF w o u l d have t o a c c o u n t f o r t h e d i s t a n c e t h e a r t i c u l a t o r s have t o move from t h e r e s t p o s i t i o n as w e l l as f o r c r i t i c a l t i m e d e l a y s . I n t h e p r e s e n t s t u d y , v o w e l c o n t e x t , w h i c h t u r n e d o u t t o be a p o s s i b l e s o u r c e o f v a r i a t i o n o f ' i n -c r e a s e s ' f o r v o w e l s , was n o t c o n t r o l l e d w e l l enough , so t h a t no such h y p o t h e s i s c an be o f f e r e d . 4 6.3 R e l a t i v e Change o f Consonan t s I n g e n e r a l , c o n s o n a n t s t e n d e d t o be ' d e c r e a s e d ' i n t h e SLOW SAF c o n d i t i o n , whereas v o w e l s showed an ' i n -c r e a s e ' . The e f f e c t was s t a t i s t i c a l l y s i g n i f i c a n t beyond the 0.01% l e v e l w i t h one e x c e p t i o n f o r t he t h r e e s u b j e c t s . Consonan t s t ended t o be ' d e c r e a s e d ' a l s o i n t h e SLOW DAF and FAST DAF c o n d i t i o n s b u t n o t as c o n s i s t e n t l y o r as s i g n i f i c a n t l y as i n the SLOW SAF c o n d i t i o n . T h i s was a l s o t r u e f o r t h e a n a l y z e d m a i n e x p e r i m e n t p a s s a g e . I t has been s u g g e s t e d when t h e g r e a t e r ^ inc reases f o r / d / i n t h e SLOW c o n d i t i o n s were d i s c u s s e d , t h a t an e n v i r o n m e n t w h i c h r e s u l t s i n a l o n g e r segment d u r a t i o n , a l s o appea r s t o r e s u l t i n g r e a t e r ' i n c r e a s e s ' a t s l o w e r r a t e s f o r t h a t segment . The q u e s t i o n was a s k e d whe the r l o n g e r segments a t s l o w e r r a t e s o f speech t e n d t o be - 80 -r e l a t i v e l y more p r o l o n g e d t h a n s h o r t e r s egmen t s . I f t h i s i s i n f a c t t h e ca se t h e n i t w o u l d seem r e a s o n a b l e t h a t c o n s o n a n t s , i n p a r t i c u l a r n o n c o n t i n u a n t s , s h o u l d be ' d e -c r e a s e d ' o r l e s s ' i n c r e a s e d ' i n c o m p a r i s o n w i t h v o w e l s . Under DAF a number o f o t h e r f a c t o r s must be c o n -s i d e r e d . A d i s c u s s i o n f o l l o w s a f t e r t h e r e s u l t s o f t h e c o n s o n a n t a n a l y s i s a r e r e p o r t e d . I n t h e s t a t e m e n t s b e l o w , ' i n i t i a l ' and ' f i n a l ' w i l l r e f e r n o t n e c e s s a r i l y j u s t t o t h e f i r s t o r l a s t c o n s o n a n t i n t h e s y l l a b l e b u t w i l l mean p r e - o r p o s t v o c a l i c r e s p e c t i v e l y . F i g u r e 6 .5 shows t h e ave rage RC f o r ' i n i t i a l ' c l o s u r e and ' f i n a l ' s t o p s , and f o r ' i n i t i a l ' / m / and ' f i n a l ' n a s a l s . As can be s e e n , ' i n i t i a l ' c l o s u r e and ' i n i t i a l ' / m / e i t h e r ' i n c r e a s e d ' more under the DAF c o n d i t i o n s o r ' d e c r e a s e d ' l e s s t h a n i n the SLOW SAF c o n d i t i o n . , ' F i n a l ' n a s a l s c o n s i s t e n t l y ' i n c r e a s e d ' i n t h e SLOW SAF c o n d i t i o n and e i t h e r ' i n c r e a s e d ' l e s s o r ' d e c r e a s e d ' i n t h e DAF c o n d i t i o n s . As can be s e e n , no c o n s i s t e n t p a t t e r n emerged f o r t h e ' f i n a l ' v o i c e l e s s s t o p s . I t w i l l be remembered t h a t ' i n i t i a l ' c l o s u r e r e -f e r s i n t h i s s t u d y t o the c l o s u r e p a r t o f an ' i n i t i a l ' s t o p o n l y , whereas ' f i n a l ' s t o p i n c l u d e s the r e l e a s e o f t h e c l o s u r e and a s p i r a t i o n . A n a l y s i s o f t he passage r e v e a l e d t h a t ' i n i t i a l ' / b / was a l s o i n c r e a s e d under t h e DAF c o n -d i t i o n s , t h e i n c r e a s e i n t h e DAF c o n d i t i o n s b e i n g h i g h l y s i g n i f i c a n t l y d i f f e r e n t f rom t h e SLOW SAF c o n d i t i o n . I n t h e s e n t e n c e s , where no s u c h o b s e r v a t i o n was made, / b / o c c u r r e d o n l y a f t e r a c o n s o n a n t p r e v o c a l i c a l l y , whereas i n - 81 -• I n i t i a l ' v o i c e l e s s c l o s u r e SUBJECT I • i SLOW SAF | | SLOW DAF FAST DAF SUBJECT 2 1 SUBJECT 3 SUBJECT (PASSAGE) ' F i n a l ' ' I n i t i a l ' ' F i n a l ' v o i c e l e s s / m / N a s a l s s t o p s F i g u r e 6 . 5 . R e l a t i v e change i n ' i n i t i a l ' v o i c e l e s s c l o s u r e , ' f i n a l ' v o i c e l e s s s t o p s , ' i n i t i a l ' / m / and ' f i n a l ' n a s a l s . - 82 -the passage /b/ oc c u r r e d o n l y w o r d - i n i t i a l l y . F i g u r e 6.6 shows the r e l a t i v e change f o r a s p i r a t i o n a s s o c i a t e d w i t h the r e l e a s e of ' i n i t i a l ' v o i c e l e s s s t o p s . As can be seen, a s p i r a t i o n 'decreased' f o r a l l s u b j e c t s i n a l l c o n d i t i o n s . However, when between-condition d i f f e r e n c e s i n r e l a t i v e change f o r a s p i r a t i o n are examined, i t can be seen i n F i g -ure 6.6 t h a t s u b j e c t s 1 and 2 showed an even f u r t h e r 'de-crease' i n a s p i r a t i o n i n the DAF c o n d i t i o n s , whereas sub-j e c t 3 showed a l e s s e r 'decrease*. Table VI shows the s t a t i s t i c a l s i g n i f i c a n c e of these o b s e r v a t i o n s . Subject 3 d i f f e r e d f u r t h e r from s u b j e c t s 1 and 2 i n t h a t f r i c a -t i v e s were e i t h e r more 'i n c r e a s e d ' or l e s s ' d e c r e a s e d 1 i n the DAF c o n d i t i o n s than i n the SLOW SAF c o n d i t i o n ; ( s i g n i f i c a n t a t the .05% l e v e l i n the SLOW DAF c o n d i t i o n and at the .005% l e v e l i n the FAST DAJT c o n d i t i o n ) . The d i f f e r e n c e s , although i n the same d i r e c t i o n f o r s u b j e c t s 1 and 2, d i d not reach s i g n i f i c a n c e f o r these s u b j e c t s . Haggard (1971) , as quoted i n MacNeilage (1972) , found t h a t of the p o s t v o c a l i c consonants, the a b s o l u t e l y f i n a l consonants appear t o have the l o n g e s t d u r a t i o n s . In the pr e s e n t study, consonants i n t h i s p o s i t i o n were f r e q u e n t l y more ' i n c r e a s e d ' than consonants i n other p o s i -t i o n s i n the SLOW SAF c o n d i t i o n . ' F i n a l ' n a s a l s i l l u s t r a t e t h i s p o i n t , i n t h a t f o r a l l s u b j e c t s the h i g h e s t RC va l u e s f o r ' f i n a l ' n a s a l s were ob t a i n e d c o n s i s t e n t l y i n a b s o l u t e l y f i n a l p o s i t i o n . T h i s appears t o f u r t h e r c o n f i r m the impression t h a t at a slower r a t e , the normally longer - 83 -• H SLOW SAF I I SLOW DAF S 5 3 FAST DAF 0 — SUBJECT I SUBJECT 2 S U B J E C T 3 F i g u r e 6 . 6 . R e l a t i v e change i n a s p i r a t i o n i n t h e SLOW S A F , SLOW DAF and FAST DAF c o n d i t i o n s w i t h r e s p e c t t o t h e NORMAL CONDITION. - 84 -SLOW DAF FAST DAF SLOW SAF S u b j e c t 1 2 3 NS * * * * NS T a b l e V I . B e t w e e n - c o n d i t i o n d i f f e r e n c e s i n r e l a t i v e change o f a s p i r a t i o n a f t e r ' . i n i t i a l ' v o i c e l e s s c l o s u r e . - 85 -segments are 'in c r e a s e d ' more than normally s h o r t e r seg-ments, o r 'decreased' l e s s . I f t h i s impression i s t r u e , then i t would be expected t h a t under the SLOW SAF con-d i t i o n c l o s u r e would e x h i b i t the lowest RC v a l u e . T h i s was not always the case, p a r t i c u l a r l y not f o r v o i c e d c l o -sure. Furthermore, of the d i f f e r e n t c l o s u r e s one might ex-pect the b i l a b i a l c l o s u r e t o show a higher RC value under the SLOW SAF c o n d i t i o n than d e n t a l or v e l a r c l o s u r e s be-cause, as MacNeilage (1972) has p o i n t e d out, b i l a b i a l c l o s u r e can be maintained longer than d e n t a l or v e l a r c l o -sure s i n c e the tongue i n the l a t t e r c l o s u r e s i s needed i n the next a r t i c u l a t i o n . However, the expected sys t e m a t i c d i f f e r e n c e s i n r e l a t i v e change f o r the d i f f e r e n t c l o s u r e s were not found. I t appears then, t h a t , while i t i s tr u e t h a t i n the SLOW SAF c o n d i t i o n vowels are more'increased' than consonants and vowels i n an environment, i n which the vowel i s longer, more 'i n c r e a s e d ' than vowels i n an e n v i r -onment, i n which the vowel i s s h o r t e r , and a b s o l u t e l y f i n a l consonants more 'in c r e a s e d ' than consonants i n other p o s t -v o c a l i c p o s i t i o n s , i t i s not t r u e t h a t a l l normally longer segments are more 'i n c r e a s e d ' under the SLOW SAF c o n d i t i o n . Instead, p o s i t i o n i n the s y l l a b l e , v o i c i n g , and p l a c e and manner of a r t i c u l a t i o n , beyond a simple stop / co n t i n u a n t dimension f o r consonants, a l l appear to p l a y d i f f e r e n t i a l r o l e s i n determining ' i n c r e a s e s ' f o r consonants i n the SLOW SAF c o n d i t i o n . In order t o s p e c i f y the r o l e of each of the parameters, environment would have to be s t r i c t l y - 86 -c o n t r o l l e d . The f i n d i n g s of the consonant a n a l y s i s are best d i s c u s s e d , however, i n terms of r e a c t i o n to DAF. To sum-marize, ' i n i t i a l ' v o i c e l e s s c l o s u r e , ' i n i t i a l ' v o i c e d c l o -sure (not i n a c l u s t e r ) , ' i n i t i a l ' /m/ and f r i c a t i v e s showed a g r e a t e r ' i n c r e a s e ' or a l e s s e r 'decrease' i n the DAF c o n d i t i o n s than i n the SLOW SAF c o n d i t i o n . F u r t h e r a n a l y s i s r e v e a l e d t h a t b i l a b i a l c l o s u r e c o n t r i b u t e d the most to the observed d i f f e r e n c e s i n v o l v i n g c l o s u r e , i n t h a t b i l a b i a l c l o s u r e e x h i b i t e d most c o n s i s t e n t l y a high e r RC val u e under DAF than under SLOW SAF. I t must be p o i n t e d out here, t h a t the observed d i f f e r e n c e s i n r e l a t i v e change f o r ' i n -i t i a l ' c l o s u r e cannot be e x p l a i n e d i n terms of c o n s i s t e n t l y lower RC va l u e s f o r c l o s u r e s under the SLOW SAF c o n d i t i o n , but i n s t e a d the d i f f e r e n c e s must be a t t r i b u t e d to the DAF e f f e c t . I t w i l l be remembered t h a t Huggins (1968) found t h a t i n i t i a l v o i c e l e s s c l o s u r e grew l i n e a r l y w i t h d e l a y . ' I n i t i a l ' p o s i t i o n appears t o be a c r u c i a l parameter i n determining ' i n c r e a s e s ' under DAF. MacNeilage (1972) i n a d i s c u s s i o n o f c l o s e d loop c o n t r o l system i n speech con-cludes t h a t one cannot assume t h a t a u d i t o r y feedback p l a y s an important r o l e i n the c o n t r o l of running speech, but somatic sensory c o n t r o l i s co n s i d e r e d necessary f o r the i n i t i a t i o n of speech. "The command necessary f o r an a r t i c u l a t o r to reach a f i x e d s p e e c h - i n i t i a l p o s i t i o n must be c o n d i t i o n a l upon the pre-speech p o s i t i o n of t h a t a r t i c u l a t o r which no doubt v a r i e s from o c c a s i o n t o o c c a s i o n . " (ibid.,pp.44-45). - 87 -I t i s e n t i r e l y p o s s i b l e , t h a t i n the normal case t h i s i s the o n l y type of feedback needed f o r the i n i t i a t i o n of speech. I f the system under DAF, however, r e c e i v e s the normal somatic sensory feedback with r e s p e c t to a r t i c u l a t o r p o s i t i o n and a t the same time r e c e i v e s a i r - c o n d u c t e d audi-^-t o r y feedback which informs the system t h a t i t (the a i r -conducted a u d i t o r y feedback) i s at v a r i a n c e w i t h the som-a t i c sensory i n f o r m a t i o n , then h e s i t a t i o n might be expected. I f we furthermore assume t h a t once speech i s i n i t i a t e d an open loop system takes over, than i t i s p o s s i b l e t h a t under DAF the beginning of a speech u n i t should be prolonged r e l a t i v e l y more than would be expected f o r a slower r a t e of speech. T h i s does not e x p l a i n the g r e a t e r ' i n c r e a s e s ' f o r vowels. However, s i n c e vowels were more 'in c r e a s e d ' a l s o a t the slower r a t e of speech under SAF, t h i s phenomen-on cannot be a t t r i b u t e d to DAF but must be c o n s i d e r e d t y p i -c a l of a slower r a t e of speech i n g e n e r a l . 5 . . 6.3 R e p e t i t i o n s F i g u r e 6.7 shows the number of r e p e t i t i o n s of d i f -f e r e n t d u r a t i o n s f o r each s u b j e c t i n the FAST DAF c o n d i t i o n and the cumulative % r e p e t i t i o n s . The graphs r e v e a l e d t h a t l e n g t h o f the repeated segments, as d e f i n e d i n chapter 5, c o r r e l a t e d w i t h the l e n g t h of delay under which they were produced. As can be seen, s u b j e c t 1 repeated more f r e q u e n t l y than s u b j e c t 2 and s u b j e c t 2 more f r e q u e n t l y than s u b j e c t 3. I t might be mentioned here t h a t the l a t t e r 2 7 -o b 6 -i— Q. ° rr 4 -cr u CD 2 -O -I I I D U R A T I O N I 2 5 I 7 5 I 125 I 175 I 2 2 5 I 2 7 5 I 3 2 5 I 3 7 5 I 4 2 5 O 5 0 100 150 2 0 0 2 5 0 3 0 0 3 5 0 4 0 0 S I I I I I I I I I I I | I I I I 2 5 I 7 5 I 125 I 175 ' 2 2 5 I 2 7 5 ' 3 2 5 0 5 0 100 150 2 0 0 2 5 0 3 0 0 I I I 1 I 1 I 1 I 1 I 1 I I 2 5 I 7 5 I 125 I 175 I. 2 2 5 ' 2 7 5 I 0 5 0 100 150 2 0 0 2 5 0 3 0 0 100 — 2 9 0 -o P 8 0 -7 0 -tu CL UJ DC 6 0 -4 0 -C 3 0 -< 3 O 2 0 -10-0 — D U R A T I O N I 2 5 I 7 5 I 125 I 175 I 2 2 5 I 2 7 5 I 3 2 5 I 3 7 5 I 4 2 5 0 5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0 3 5 0 4 0 0 S U B J E C T I D e l a y u sed i n t he e x p e r i m e n t : 2 4 0 I 2 5 I 7 5 I 125 I 175 I 2 2 5 I 2 7 5 I 3 2 5 0 5 0 1 0 0 150 2 0 0 2 5 0 3 0 0 S U B J E C T 200 oo 00 I I I I I I I I I I' I I I I 2 5 I 7 5 I 125 I 175 I 2 2 5 I 2 7 5 I 0 5 0 100 150 2 0 0 2 5 0 3 0 0 S U B J E C T 3 230 F i g u r e 6 . 7 . Number o f r e p e t i t i o n s and c u m u l a t i v e % r e p e t i t i o n s i n the FAST DAF c o n d i t i o n . - 89 -f i n d i n g was a l s o t r u e f o r other a d d i t i o n s to the expected sequence of a r t i c u l a t i o n . Subject 1 e x h i b i t e d by f a r the most a d d i t i o n s u n r e l a t e d to the t e x t and r a t h e r b i z a r r e h. i n nature, e.g., /kam fa&e*-/ became /k ambagl f ep af aoa"/• In the SLOW DAF c o n d i t i o n o n l y a few i s o l a t e d r e p e t i t i o n s o c c u r r e d which i s i n agreement w i t h MacKay's (1968) f i n d i n g t h a t under DAF a t a slower r a t e r e p e t i t i o n s decrease i n number. In view of the r a r i t y w i t h which m u l t i p l e repe-t i t i o n s have been observed f o r E n g l i s h speakers under DAF by p a s t experimenters, i t might be noted here, t h a t although s u b j e c t s 2 and 3 p r i m a r i l y e x h i b i t e d double r e p e t i t i o n s , s u b j e c t 1 f r e q u e n t l y produced m u l t i p l e r e p e t i t i o n s (up to f i v e r e p e t i t i o n s i n one i n s t a n c e ) . T h i s does suggest t h a t m u l t i p l e r e p e t i t i o n s are not p e c u l i a r t o the Russian speak-ers i n the Kozhevnikov and C h i s t o v i c h (1965) study. Fur-thermore, these r e p e t i t i o n s were always, r e p e t i t i o n s of open s y l l a b l e s , which i s i n agreement wi t h the f i n d i n g s of the above authors. F i n a l l y , i t was observed t h a t when a vowel was repeated a t the b e g i n n i n g of a s y l l a b l e , e.g., / i ? i s t / , a g l o t t a l stop was i n s e r t e d , and when a vowel was repeated a f t e r a consonant, e.g., /kaham/, an /h/ was i n s e r t e d . L a r y n g e a l i z a t i o n f r e q u e n t l y preceded a vowel i n s y l l a b l e -i n i t i a l p o s i t i o n i n the DAF c o n d i t i o n s . Stromsta (1959) found t h a t s i d e - t o n e , which was d i s t o r t e d by a l t e r i n g i t s frequency components or i t s a r r i v a l phases at the two e a r s , produced a blockage i n phonation while phonating a vowel i n f a l s e t t o . Van Riper - 90 -(1971), who, l i k e many others ( f o r a review see Timmons and Boudreau,1972), c o n s i d e r n a t u r a l and a r t i f i c i a l s t u t t e r to be s i m i l a r behaviours, h y p o t h e s i z e d t h a t asynchronies i n t i m i n g of a n t a g o n i s t i c muscle groups a t the l a r y n g e a l l e v e l are r e s p o n s i b l e f o r the observed s t u t t e r . In support of such a theory, Freeman and Us h i j i m a (1974) on the b a s i s of t h e i r experiments, s t a t e : " f l u e n t u t t e r a n c e i s c h a r a c t e r i z e d by p r e -c i s e balance and t i m i n g of l a r y n g e a l abductor and adductor f o r c e s . In f l u e n t u t t e r a n c e abductor and adductor f o r c e s a c t r e c i p r o c a l l y , whereas, i n s t u t t e r e d u t t e r a n c e , t h i s r e c i -p r o c i t y i s d i s r u p t e d . In many s t u t t e r e d u t t e r a n c e s the l a t e r a l c r i c o a r y t e n o i d - g e n -e r a l l y presumed to be an adductor, w i t h the s p e c i f i c f u n c t i o n of medial compression-achieved abnormally h i g h l e v e l s o f a c t i v i t y . " ( i b i d . , p. S80). The l a r y n g e a l i z a t i o n and i n s e r t i o n o f g l o t t a l stops observed under DAF i n t h i s study and a l s o the 'decrease' i n a s p i r a -t i o n under DAF a f t e r ' i n i t i a l ' v o i c e l e s s c l o s u r e would tend to c o n f i r m t h a t the e f f e c t s of DAF on speech are not u n l i k e those of n a t u r a l or a r t i f i c i a l s t u t t e r . I t i s of p a r t i c u l a r i n t e r e s t i n t h i s r e s p e c t t h a t those s u b j e c t s most a f f e c t e d by DAF showed a g r e a t e r 'decrease' of a s p i r a t i o n under DAF than i n the SLOW SAF c o n d i t i o n , whereas the s u b j e c t l e a s t a f f e c t e d showed a l e s s e r 'decrease'. No e x p l a n a t i o n can be o f f e r e d a t t h i s time f o r the d i f f e r e n t i a l i n s e r t i o n of g l o t t a l stops and /h/. Nor can the b i z a r r e i n s e r t i o n s i n t o the expected sequence of a r t i c u l a t i o n be reasonably e x p l a i n -ed. The c o r r e l a t i o n of the d u r a t i o n s of repeated segments w i t h the de l a y under which they were produced, i s i n - 91 -agreement w i t h the f i n d i n g s r e p o r t e d by Huggins (1968). In summary, the i n v e s t i g a t i o n of i n s e r t i o n s i n t o the e x p e c t e d sequence o f a r t i c u l a t i o n s u g g e s t s t h a t (a) m i s t i m i n g a t the l a r y n g e a l l e v e l a c c o u n t s f o r some o f the speech d i s t u r b a n c e s o b s e r v e d under DAF, (b) t ime r e l a t i o n -s h i p s are a c r u c i a l a s p e c t o f b e h a v i o u r under DAF i n t h a t the d u r a t i o n s of r e p e t i t i o n s are r e l a t e d to the d e l a y under which they were produced and (c) m u l t i p l e r e p e t i t i o n s c o n s t i t u t e s a b e h a v i o u r which must i n the l a s t a n a l y s i s be e x p l a i n e d i n terms of i n d i v i d u a l d i f f e r e n c e s . " A major c h a l l e n g e t h a t i s emerging f o r r e s e a r c h e r s i n speech p h y s i o l o g y , when they use s e v e r a l s u b j e c t s i n t h e i r e x p e r -i m e n t s , i s t o d e v e l o p speech p r o d u c t i o n t h e o r i e s which take t h e s e i n d i v i d u a l d i f f e r e n c e s i n t o a c c o u n t r a t h e r t h a n i g n o r i n g t h e m . " ( M a c N e i l a g e , 1972 ,pp. 22 -23) . 6.4 Summary and C o n c l u s i o n s T h i s s tudy has examined and compared speech a t a normal r a t e and a t a slow r a t e under synchronous feedback and speech under DAF a t b o t h a slow and m a x i m a l l y f a s t r a t e . I t was found t h a t c o n s i d e r a b l e i n d i v i d u a l d i f f e r -ences e x i s t i n terms of the degree of speech d i s t u r b a n c e produced i n the s u b j e c t s under DAF. A r e c i p r o c a l r e l a t i o n -s h i p between p r o l o n g a t i o n and r e p e t i t i o n , i . e . , the more o v e r a l l p r o l o n g a t i o n , the fewer the r e p e t i t i o n s , e x i s t e d o n l y when r a t e was v a r i e d under DAF. A t a maximum r a t e , s u b j e c t s who p r o l o n g e d more a l s o r e p e a t e d f r e q u e n t l y . In o t h e r t e r m s , i t was not t r u e t h a t the s u b j e c t who r e p e a t e d - 92 -most f r e q u e n t l y , showed the l e a s t amount of o v e r a l l p r o -l o n g a t i o n . R e p e t i t i o n s a t the maximum r a t e under DAF ap-peared t o be r e l a t e d t o the del a y under which they were produced. While the h y p o t h e s i s t h a t under SLOW SAF vowels are prolonged more than consonants was s u b s t a n t i a t e d , i t co u l d not be confirmed t h a t under SLOW SAF w i t h i n the c l a s s of vowels, c l o s e vowels are prolonged more than open vow-e l s . The hy p o t h e s i s t h a t under SLOW SAF c o n t i n u a n t con-sonants are prolonged more than o b s t r u e n t s was a l s o not s u b s t a n t i a t e d . The hypothesis t h a t under DAF vowels and f r i c a t i v e s are prolonged the most and t h a t p o s i t i o n w i t h i n the s y l l a b l e a f f e c t s the d u r a t i o n i n c r e a s e s of each sound c l a s s s e l e c t -i v e l y was confirmed. The hypothesis t h a t speech under SLOW SAF would d i f f e r from speech under DAF was s u b s t a n t i a t e d i n t h a t under DAF open back vowels, f r i c a t i v e s , i n i t i a l v o i c e l e s s c l o -sure and a l l i n i t i a l b i l a b i a l c l o s u r e was r e l a t i v e l y more prolonged then under SLOW SAF whereas under SLOW SAF con-sonants i n f i n a l p o s i t i o n were r e l a t i v e l y more prolonged than under DAF. I t had a l s o been hypothesized t h a t s t r e s s would determine r e l a t i v e amount of p r o l o n g a t i o n under SLOW SAF. I t was found t h a t under SLOW SAF and under SLOW DAF and to a l e s s e r extent under FAST DAF each s y l l a b l e formed a beat i n the rhythmic s u c c e s s i o n of speech u n i t s , i . e . , there - 93 -a r e no u n s t r e s s e d segments a t v e r y s low r a t e s o f speech. The b eat m a n i f e s t s i t s e l f i n r e l a t i v e i n c r e a s e s i n d u r a t i o n o f t h e vowel i n the s y l l a b l e and i n c r e a s e d speech power i n comparison w i t h speech a t a normal r a t e . Thus, n o r m a l l y u n s t r e s s e d segments, e.g., f u n c t i o n words, a t a v e r y slow r a t e i n c r e a s e r e l a t i v e l y more i n d u r a t i o n t h a n n o r m a l l y s t r e s s e d segments. I n v i e w o f t h e d i s c u s s i o n (Chapter 2 ) , i t can be r e a s o n a b l y assumed t h a t s l o w i n g a t a v o l u n t a r i l y slowed r a t e under SAF i s not due t o s l o w i n g a t a r e f l e x l e v e l , i . e . , a p e r i p h e r a l l e v e l , b u t r a t h e r t h a t such a v o l u n t a r y s l o w i n g must t a k e p l a c e a t a c e n t r a l l e v e l , such as t h e motor c o n t r o l programme l e v e l proposed by A l l e n (1973). When t h e r a t e i s slowed under DAF by c o m p l y i n g w i t h t h e DAF e f f e c t , s l o w i n g can be s a i d t o be v o l u n t a r y as w e l l . Thus, s i m i l a r i t i e s i n t h e r e s u l t i n g b e h a v i o u r might be e x p e c t e d . A t a m a x i m a l l y f a s t r a t e under DAF no v o l u n t a r y s l o w i n g t a k e s p l a c e . Any s l o w i n g must be a t t r i b u t e d t o t h e DAF e f f e c t . One m ight assume t h a t t h e d i f f e r e n c e s i n speech b e h a v i o u r under SLOW SAF and under DAF a r e a t t r i b u t -a b l e t o d i f f e r e n c e s i n t h e l e v e l a t which s l o w i n g t a k e s p l a c e . I f one assumes t h a t v o l u n t a r y r a t e changes a r e de-t e r m i n e d a t a c e n t r a l l e v e l , t h a n th e o b s e r v e d d i f f e r e n c e s between v o l u n t a r i l y slowed speech and DAF-slowed speech might be a t t r i b u t a b l e t o i n t e r f e r e n c e a t t h e r e f l e x l e v e l , w h i l e o b s e r v e d s i m i l a r i t i e s m ight be a t t r i b u t a b l e e i t h e r t o i n t e r f e r e n c e a t a c e n t r a l l e v e l , o r a l s o t o r e f l e x l e v e l - 94 -i n t e r f e r e n c e , i f r e f l e x l e v e l i n t e r f e r e n c e i s s i m i l a r i n these r e s p e c t s (from the p o i n t of view of r e s u l t s ) to cen-t r a l i n t e r f e r e n c e . In any event, one cannot deny t h a t the r e f l e x l e v e l i s i n v o l v e d i n DAF-induced changes i n the speech behaviour, e s p e c i a l l y i n view of the involvement of the l a r y n x as evidenced by f r e q u e n t l a r y n g e a l i z a t i o n under DAF. The p r e v o c a l i c r a t h e r than p o s t v o c a l i c slowing observed under DAF and not under SLOW SAF seems to i n d i c a t e t h a t the s y l l a b l e i s a monitored u n i t i n speech p r o d u c t i o n under DAF; once speech i s i n i t i a t e d , i t i s a b l e to procede towards i t s c o n c l u s i o n , the next i n t e r f e r e n c e being n o t i c e -a b l e a g a i n a t the i n i t i a t i o n o f the next speech u n i t . 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TIMMONS, B.A.,.and BOUDREAU,J.P. ( 1 9 7 2 ) . " A u d i t o r y F e e d -b a c k as a M a j o r F a c t o r i n S t u t t e r i n g , " J . S p e e c h H e a r i n g D i s . 3_7, 476-484. VAN RIPER, C. (-1971) . The N a t u r e o f S t u t t e r i n g ( P r e n t i c e -H a l l , I n c . , E n g l e w o o d C l i f f s , N . J . ) . YATES, A . J . ( 1 9 6 5 ) . " D e l a y e d A u d i t o r y F e e d b a c k and Shadow-i n g , " Q u a r t . J . Exp. P s y c h o l . 1_7, 125-131. ZELNIKER, T. ( 1 9 7 1 ) . " P e r c e p t u a l A t t e n u a t i o n o f an I r r e l e -v a n t A u d i t o r y V e r b a l I n p u t as M e a s u r e d by an I n v o l u n t a r y V e r b a l R e s p o n s e i n a S e l e c t i v e - A t t e n t i o n Task,". J . Exp. P s y c h o l . 87, 52-56. - 98 -Number of Delay Level or Gain of Error and Duration Experimenter Subjects in msec. feedback signal Measures Lee (1950b) 5 0,40,140,280 unspecified (high Total duration enough to produce sub-stantial disturbance Black (1951) 22 0 to 300 in 85-90 dB at earphones Mean of total duration 30 msec. increments Fairbanks 16 0,100,200, 30 dB above an arbitrary a) total instances of error, (1955) 400,800 reference b) total duration c) rate of instance of error, d) correct word rate, e) total word rate f) error word rate Fairbanks and" Guttman (1958) (based on Fairbanks (1955) experiments) a) classification of errors according to type, b) number of phonemes per error Chase (1958) 20 0,216 20 dB above the vocal Number of times [b] was output repeated in 5 sec. Kozhevnikov 5 0,100,210, 115 dB at earphones a) phonemes per sec., and Chistovich 300,470 b) duration of repeated (1965) syllables and of segments within syllables, c) number of repetitions in any one instance of repe-tition. Number of Delay Level or Gain of Error and Duration Experimenter Subjects i n msec. feedback signal Measures MacKay 1968 a) 13 200,263 45 dB above vocal a) Number of repetitions output per syllable b) 13 0,100,150,200, 45 dB above vocal b) Total duration 263,375,524,750 output Number of correct syllables Huggins (1968) 1 0,80-400 i n 10 35 dB above vocal a) total duration msec increments output (70-75 dB b) number of repetitions speaking level) c) acoustic segment dur-ations Fletcher and 50 i n 200 35 dB above vocal Number of times a par-Yates (1971) experiments I, output ticular sound was II and I I I , 48 repeated i n 5 seconds in experiment IV. Sussman and 4 0,100,200,300, unspecified (high Extent of Smith (1971) 400 enough to mask bone- a) jaw opening conducted feedback) b) jaw velocity during opening and closing c) duration of jaw activity Robinson 4 0,200,225,250, unspecified (feedback Number of errors (1972) 275,300 signal was accompanied by "pink" noise masker) Appendix B P i l o t Study Passage [Once upon a time], a number of mice c a l l e d a meeting, to decide upon the best means of ridding themselves of a cat that had k i l l e d so many of them. Various plans were talked about, but none of them chosen. A young mouse came forward, and said that a b e l l should be hung round the tyrant's neck. Then they would a l l hear the cat coming, and so be able to escape. The suggestion was received with pleasure by a l l , u n t i l a thoughtful old mouse got up and said, "I consider the plan a very clever one. But I should l i k e to know, who i s going to put the b e l l on the cat?" [It i s easier to make a suggestion than to carry i t out.] The sentences i n brackets served as frame and were not analyzed. The passage was broken up into the following phrases for purposes of analyses: Phrase 1 . a number of mice c a l l e d a meeting, Phrase 2 . to decide upon the best means Phrase 3 . of ridding themselves of a cat Phrase 4. that had k i l l e d so many of them. Phrase 5 . Various plans were talked about, Phrase 6 . but none of them chosen. Phrase 7 . A young mouse came forward, - 1 0 1 -- 1 0 2 -P h r a s e 8. a n d s a i d t h a t a b e l l s h o u l d b e h u n g r o u n d t h e t y r a n t ' s n e c k . P h r a s e 9. T h e n t h e y w o u l d a l l h e a r t h e c a t c o m i n g , a n d s o b e a b l e t o e s c a p e . P h r a s e 1 0 . T h e s u g g e s t i o n w a s r e c e i v e d w i t h p l e a s u r e b y a l l . P h r a s e 1 1 . u n t i l a t h o u g h t f u l o l d m o u s e g o t u p a n d s a i d , P h r a s e 1 2 . " I c o n s i d e r t h e p l a n a v e r y c l e v e r o n e . " P h r a s e 1 3 . B u t I s h o u l d l i k e t o know, who i s g o i n g t o p u t t h e b e l l o n t h e c a t ? " Appendix C Screening Passage We know the shocks are p a i n f u l ; we have t r i e d them on o u r s e l v e s and we know t h a t they h u r t . But i t i s s t r e s s f u l f o r the person who does the shocking too. You may have used shock s u c c e s s f u l l y w i t h a hundred k i d s , but you are s t i l l apprehen-s i v e about i t ; you always t h i n k t h a t maybe t h i s k i d w i l l be the exce p t i o n ; maybe you w i l l h u r t him and i t won't do any good. But then when you shock him and you see the s e l f - d e s t r u c t i v e behaviour stop, i t i s tremendously rewarding. - 103 -Appendix D Main Experiment Passage [Some time ago, a group of mice c a l l e d a meeting to d ecide upon a good means of r i d d i n g themselves permanently of t h a t awful k i l l e r c a t.] Many a p l a n was t a l k e d over, when an i n s i g n i f i c a n t l i t t l e mouse came forward and remarked t h a t they should t i e a b e l l around the t y r a n t ' s neck. Then i n f u t u r e they would hear t h a t c r a f t y f e l i n e approach and so be ab l e to escape. The su g g e s t i o n was r e c e i v e d w i t h much p l e a s u r e , u n t i l a t h o u g h t f u l mouse s a i d , "I c o n s i d e r the whole p l a n a c l e v e r one. But I should l i k e to know, who w i l l p u t the b e l l on the c a t ? " [ I t i s e a s i e r to make a suggestion than to c a r r y i t out.] The sentences i n b r a c k e t s served as frame and were not a nalyzed. The passage was broken up i n t o the f o l l o w i n g phrases f o r purposes of a n a l y s i s : Phrase 1: Many a p l a n was t a l k e d over, Phrase 2: when an i n s i g n i f i c a n t l i t t l e mouse came forward Phrase 3: and remarked t h a t they should t i e a b e l l around the t y r a n t ' s neck. Phrase 4: Then i n f u t u r e they would hear t h a t c r a f t y f e l i n e approach - 104 -- 105 -Phrase 5: and so be abl e to escape. Phrase 6: The suggestion was r e c e i v e d w i t h much p l e a s u r e , Phrase 7: u n t i l a t h o u g h t f u l mouse s a i d , Phrase 8: "I c o n s i d e r the whole p l a n a c l e v e r one. Phrase 9: But I should l i k e to know, who w i l l put the b e l l on the c a t ? " Appendix E Main Experiment Sentences Sentence 10 " [ I n an average t h e a t e r a c t o r s are working /o/ on a scene j u s t l i k e the f o l l o w i n g : ] E n t h r a l l e d Maud's c a u t i o u s daughter pauses, f o r the ch a l k scrawl on the w a l l t a l k s of awesome hawk's claws. [ I t i s q u i t e c l e a r t h a t such scenes must be c a r e f u l l y executed.]" Sentence 11 " [ I n an average t h e a t e r a c t o r s are working / i / on a scene j u s t l i k e the f o l l o w i n g : ] Seated i n between l e a f y t r e e s the keen Ea s t G r e e n v i l l e people see the three greedy teams each r e t r e a t s p e e d i l y . [ I t i s q u i t e c l e a r t h a t such scenes must be c a r e f u l l y executed.]" Sentence 12 " [ I n an average t h e a t e r a c t o r s are working / a / on a scene j u s t l i k e the f o l l o w i n g : ] At h a l f p a s t one the calm f a t h e r passes gas masks up the s h a f t a f t e r the c a s t l e s t a f f rushed up the path. [I t i s q u i t e c l e a r t h a t such scenes must be c a r e f u l l y executed.]" - 106 -- 107 -Sentence 13 " [ I n an average t h e a t e r a c t o r s are working on /u/ a scene j u s t l i k e the f o l l o w i n g : ] Soon the two f o o l s who choose crude t o o l s l o s e to the smooth snoops who use goof-proof r u l e s to shoot snooker p o o l . [ I t i s q u i t e c l e a r t h a t such scenes must be c a r e f u l l y e x e c uted.]" The sentences i n b r a c k e t s served as frame and were not analyzed. Appendix F Symbols used i n the Study Consonants B i l a b i a l L a b i o - Dental and Palato- Pala- Velar G l o t t a l Dental Al v e o l a r Alveolar t a l Plosives p,b Nasals m Laterals F r i c a t i v e s p F r i c t i o n l e s s Continuants and Semi-vowels w f,v t , d e,8/s,z j , ^ Vowels front back close i u i o e o e e A O ae v open a D i a c r i t i c a l Marks: = unreleased ( = s y l l a b i c = v o i c i n g • ' =• stress v 0 = breath h = a s p i r a t i o n - 108 -Appendix' G 6 0 0 — 1 3 6 II 14 16 2 0 2 2 2 4 2 7 3 0 3 3 3 8 4 0 4 2 4 6 4 8 51 5 3 5 8 6 3 6 7 6 9 71 2 5 10 13 15 19 21 2 3 2 6 2 9 3 2 3 7 3 9 41 4 5 4 7 5 0 5 2 5 7 6 2 6 6 6 8 7 0 7 4 NORMAL FAST DAF SLOW SLOW DAF Subject 1 , Sentence 12 - 109 -- 110 -4 0 0 — M S E C , 1 3 6 II 14 16 20 22 24 27 30 33 38 4 0 42 46 4 8 51 53 58 63 67 6 9 71 S Y L . - - - - - - -2 5 10 13 15 19 21 23 26 29 32 37 39 41 4 5 4 7 50 52 57 62 66 68 70 74 NORMAL FAST DAF SLOW SLOW DAF Subject 2, Sentence 12 - I l l -5 0 0 4 0 0 3 0 0 -2 0 0 1 0 0 — M S E C . 0 . S Y L . 3 6 | , | , , . | i | • |- . | i | i | i | i 14 16 2 0 2 2 2 4 2 7 3 0 3 3 3 8 4 0 4 2 4 6 4 8 51 5 3 5 8 6 3 6 7 6 9 71 2 5 10 13 15 19 21 2 3 2 6 2 9 3 2 3 7 3 9 41 4 5 4 7 5 0 5 2 5 7 6 2 6 6 6 8 7 0 7 4 N O R M A L — F A S T D A F — S L O W — S L O W D A F S u b j e c t 3, Sentence 12 - 112 -7 0 0 — M S E C . 0 — | i | . | , | , | i | I | , | . | i | i | i | I 4 6 9 13 15 19 2 4 2 9 3 2 3 5 3 7 41 4 6 4 8 51 5 4 5 9 6 3 6 6 6 9 7 2 7 5 S Y L . - - - - - - - - -3 5 8 12 14 18 2 3 2 8 31 3 4 3 6 4 0 4 5 4 7 5 0 5 3 5 8 6 2 6 5 6 8 71 7 4 7 8 N O R M A L F A S T D A F S L O W S L O W D A F Subject 1, Sentence 13 - 113 _ 5 0 0 — 4 0 0 — 3 0 0 — 2 0 0 - \ - \ 1 0 0 — -A V/ \ A V I V / \\ i I M S E C . 0 — SYL. I |• i | I | i | i | I | ' | • ' | i | 1 | 1 | I 4 6 9 13 15 19 2 4 2 9 3 2 3 5 3 7 41 4 6 4 8 51 5 4 5 9 6 3 6 6 6 9 7 2 7 5 3 5 8 12 14 18 2 3 2 8 31 3 4 3 6 4 0 4 5 4 7 5 0 5 3 5 8 6 2 6 5 6 8 71 7 4 7 8 N O R M A L F A S T D A F S L O W S L O W D A F •Subject 2, Sentence 13 - i i U -600 — M S E C | I | I | I | I | I | I | I | I | I | I | I | I 4 6 9 13 15 19 24 29 32 35 37 4J 46 48 51 54 59 63 66 69 72 7! SYL. 3 5 8 12 14 18 23 28 31 34 36 40 45 47 50 53 58 62 65 68 71 74 78 NORMAL FAST DAF SLOW SLOW DAF Subject 3, Sentence 13 400 — | I I I | I I I I | I I I I | I II I | I I I I | I I I I | I I I I | I I I I | I I I I | I I I I | I I I I | I I I I | I I M | I I I I | I SEG. I 5 10 15 20 25 30 35 40 45 50 55 60 65 70 Subject 1, Sentence 12 NORMAL FAST DAF