Temporal integration of visual form information in adult dyslexia
by Roberta Lee Winters
A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in
Psychology
Montana State University
© Copyright by Roberta Lee Winters (1987)
Abstract:
Temporal integration of visual form information in dyslexic and nondyslexic adults was investigated to
determine whether the dyslexics demonstrate problems in temporal integration similar to the problems
that have been found in childhood dyslexia. Using procedures derived from signal detection theory,
sensitivity to sequentially presented form information was determined for the two groups. The principle
result of this study was that the sensitivity of the normals to sequencing was superior (i.e., better
temporal acuity) to that of dyslexics when parts of a stimulus were presented contiguously in space.
This result suggests that, under certain conditions, temporal processing of form information is slower
within the visual systems of dyslexics. Based on this result, it is concluded that a temporal integration
deficit exists in adult dyslexia which is similar to that found in childhood dyslexia. TEMPORAL INTEGRATION OF VISUAL
FORM INFORMATION IN
ADULT DYSLEXIA
. by
R o b e rta Lee W in te rs
A t h e s i s su b m itte d in p a r t i a l f u l f i l l m e n t
o f th e re q u ire m e n ts f o r th e degree
er
M aster o f S c ie n c e
in
P sy ch o lo g y
MONTANA STATE UNIVERSITY
B ozem an, M o n ta n a
J u n e I 987
main
Lia.
/V 3 7 f
APPROVAL
o f a t h e s i s s u b m i t t e d by
R o b e rta Lee W in te rs
T h i s t h e s i s h a s b e e n r e a d by e a c h member o f t h e t h e s i s c o m m i t t e e
a n d h a s b e e n f o u n d t o be s a t i s f a c t o r y r e g a r d i n g c o n t e n t , E n g l i s h
u s a g e , f o r m a t , c i t a t i o n s , b i b l i o g r a p h i c s t y l e , a n d c o n s i s t e n c y , and
i s re a d y f o r su b m iss io n to th e C o lle g e o f G ra d u ate S tu d i e s .
A pproved f o r t h e M ajo r D e p artm en t
6 /z-y/? 7 _______
H e a d ,M a jo r D e p a rtm e n t
D a te
A pproved f o r t h e C o lle g e o f G ra d u a te S t u d i e s
"7 ^ / -7
D a te
G r a d u a t e Dean
STATEMENT OF PERMISSION TO USE
In p re s e n tin g t h i s
m ents f o r
a m a s te r 's
th e s is in p a r tia l f u lf illm e n t of th e re q u ir e ­
d e g r e e a t M o n ta n a S t a t e U n i v e r s i t y ,
t h e L i b r a r y s h a l l m ake i t
a v a ila b le to
L i b r a r y . B r i e f q u o t a t i o n s fro m t h i s
s p e c ia l p erm issio n ,
I agree th a t
b orrow ers under r u l e s of th e
t h e s i s a re a llo w a b le w ith o u t
p r o v id e d t h a t a c c u r a t e ack n o w led g em en t o f s o u r c e
i s m ade.
P e r m i s s i o n f o r e x t e n s i v e q u o t a t i o n from o r r e p r o d u c t i o n o f t h i s
t h e s i s may be g r a n t e d by my m a j o r p r o f e s s o r , o r i n h i s a b s e n c e , by
t h e D ean o f L i b r a r i e s w h e n , i n t h e o p i n i o n o f e i t h e r , t h e p r o p o s e d
u s e o f t h e m a t e r i a l i s f o r s c h o l a r l y p u r p o s e s . Any c o p y i n g o r u s e o f
th e m a te r ia l
in t h i s
w i t h o u t my w r i t t e n
t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t be a l l o w e d 1
p erm issio n .
iv
ACKNOWLEDGMENTS
I
w o u ld l i k e t o e x p r e s s my s i n c e r e g r a t i t u d e t o e v e r y o n e who h a s ■
b een in v o l v e d , b o th d i r e c t l y and i n d i r e c t l y ,
in t h i s p r o j e c t .
In
p a r t i c u l a r , L w o u ld l i k e t o t h a n k t h e m em bers o f my c o m m i t t e e a s
th e ir
a s s i s t a n c e and s u p p o r t h as b een i n v a l u a b l e .
I w i l l a l w a y s be
g r a t e f u l t o D r . W i l l i a m D. S h o n t z , t h e c h a i r m a n o f my c o m m i t t e e , f o r
g i v i n g me t h e o p p o r t u n i t y t o w o rk i n h i s l a b a n d f o r h i s g u i d a n c e ,
su p p o rt, p a tie n c e ,
an d u n d e r s t a n d i n g .
I w o u ld a l s o l i k e t o t h a n k D r .
R o b e r t P a t t e r s o n f o r t r a n s f o r m i n g my w r i t i n g s t y l e i n t o a s t y l e t h a t
I am now p r o u d o f .
co lle a g u e ,
To D r . R i c h a r d H o r s w i l l , a t r e a s u r e d f r i e n d a n d
t h a n k you f o r a l l t h a t y o u h a v e g i v e n t o me d u r i n g t h e
l a s t th re e y ears.
In ad d itio n ,
I w o u ld l i k e t o t h a n k D r . F r e d C ady f o r w r i t i n g t h e
co m p u ter p ro g ram s and d e s i g n i n g t h e l a b o r a t o r y eq u ip m en t n e c e s s a r y
f o r t h i s e x p e r i m e n t ; Ms. S a r a h M y ers f o r h e r a s s i s t a n c e i n t h e l a b ;
a n d Ms. L a u r i e G a f f n e y f o r t e a c h i n g me a b o u t t h e d y s l e x i c p o p u l a t i o n .
And f i n a l l y ,
g ra d u a te s tu d e n t,
I w o u ld l i k e t o t h a n k my o f f i c e p a r t n e r ,
and b e s t f r i e n d ,
G regory B urns.
t h a t w i t h o u t G r e g , I n e v e r w o u ld h a v e made i t .
fe llo w
I can h o n e s tly say
Thanks G re g rg o re ^ e .
V
TABLE OF CONTENTS
ACKNOWLEDGMENTS .............................................................................................................................' i v
LIST OF TABLES ............................................................................................................................... v i
LIST OF FIGURES ..................................................................................................
ABSTRACT ................................
v ii
v iii
INTRODUCTION .......................................................................................................................................
METHOD ............................................................................................................................... -..................
I
ii
S u b j e c t s .................................................................................................................................. 11
A p p a r a t u s a n d S t i m u l i ................................................................................................. 11
P r o c e d u r e ............................................................................................................................... 11
RESULTS ..................................................
17
DISCUSSION ................................. ................... ................. ......................................................... ■ ... 22
REFERENCES CITED ....................................................................................................■____ '............25
APPENDIX
30
vi
LIST OF TABLES
T ab le
I
Page
A n a l y s i s o f V a r i a n c e C om puted o n t h e A r e a U n d e r t h e
ROC C u rv e a s a M e a s u r e o f S e n s i t i v i t y t o S e q u e n c i n g ____
18
vii
LIST OF FIGURES
F igure
1
Page
A sum m ary o f t h e H i e r a r c h y o f Many o f t h e
V i s u a l A r e a s i n t h e M acaque M o n k e y . ......................................
4
2
Illu stra tio n
...............................
13
3
A verage R e c e i v e r - O p e r a t i n g - C h a r a c t e r i s t i c C u rv es
o f N o n d y sle x ic s f o r th e E x p e rim e n ta l C o n d itio n s . . .
20
A verage R e c e i v e r r O p e r a t i n g - C h a r a c t e r i s t i c C u rv es
o f D y s l e x i c s f o r t h e E x p e r i m e n t a l C o n d i t i o n s .............
21
4
o f E x p e rim e n ta l C o n d itio n s
viii
ABSTRACT
T em poral i n t e g r a t i o n o f v i s u a l fo rm i n f o r m a t i o n i n d y s l e x i c and
n o n d y s l e x i c a d u l t s was i n v e s t i g a t e d t o d e t e r m i n e w h e t h e r t h e d y s l e x i c s
d e m o n s tr a te p ro b le m s i n te m p o ra l i n t e g r a t i o n s i m i l a r t o th e p ro b lem s
t h a t have been fo u n d i n c h ild h o o d d y s l e x i a .
U sin g p r o c e d u r e s d e r iv e d
from s i g n a l d e t e c t i o n t h e o r y , s e n s i t i v i t y t o s e q u e n t i a l l y p r e s e n t e d
f o r m i n f o r m a t i o n was d e t e r m i n e d f o r t h e tw o g r o u p s .
The p r i n c i p l e
r e s u l t o f t h i s s t u d y was t h a t t h e s e n s i t i v i t y o f t h e n o r m a l s t o
s e q u e n c i n g was s u p e r i o r ( i . e . , b e t t e r t e m p o r a l a c u i t y ) t o t h a t o f
d y s l e x i c s when p a r t s o f a s t i m u l u s w e r e p r e s e n t e d c o n t i g u o u s l y i n
space.
T h is r e s u l t s u g g e s ts t h a t , u n d er c e r t a i n c o n d i t i o n s , te m p o ra l
p r o c e s s i n g o f form i n f o r m a t i o n i s s lo w e r w i t h i n t h e v i s u a l s y s te m s o f
d y sle x ic s.
B ased on t h i s r e s u l t , i t i s c o n c lu d e d t h a t a te m p o ra l
i n t e g r a t i o n d e f i c i t e x i s t s i n a d u l t d y s l e x i a w h ich i s s i m i l a r t o t h a t
fou n d i n c h ild h o o d d y s l e x i a .
/'
I
INTRODUCTION
D y s l e x i a i s a s p e c i f i c l e a r n i n g d i s a b i l i t y t h a t i n v o l v e s an
i n a b i l i t y to re a d ,
(P a v lid is & F ish e r,
in te g ra te ,
1 9 86).
o r i n t e r p r e t th e w r i t t e n la n g u a g e
I t h a s b e e n e s t i m a t e d t h a t 5 t o 10
p e r c e n t o f th e p o p u la tio n a re a f f l i c t e d w ith th e c o n d itio n
Hynd, 19 8 4 ) ,
1986).
(Hynd &
a n d t h a t i t o c c u r s i n a l l p a r t s o f t h e w o r l d ( R aw s o n ,
For th o s e so a f f l i c t e d ,
d y s l e x i a can e x a c t a s e v e r e c o s t in
term s o f r e t a r d i n g i n t e l l e c t u a l and s o c i a l d e v e lo p m e n t, f o r th e
a b i l i t y t o r e a d a n d u n d e r s t a n d t h e w r i t t e n l a n g u a g e p l a y s an
im p o r ta n t r o l e i n d e te r m in in g w h e th e r one su c c e e d s b o th a c a d e m ic a lly
and s o c i a l l y .
T h is i s
e v i d e n c e d by t h e l a r g e num ber o f d y s l e x i c s who
a r e e i t h e r u n e m p l o y e d o r u n d e r e m p l o y e d and by t h e d i s p r o p o r t i o n a t e l y
l a r g e num ber who a r e f o u n d i n j u v e n i l e o r a d u l t c o r r e c t i o n a l
in stitu tio n s
(Jo h n so n & B la lo c k ,
1987; S c h e ib e r & T a l p e r s , 1 9 8 5 ).
B ecause o f th e d e b i l i t a t i n g e f f e c t s o f d y s le x ia ,
a ttra c te d
c o n sid e ra b le re s e a rc h sin c e i t s
T h is r e s e a r c h has l e d . t o
th e l i n g u is t i c
it
has
d i s c o v e r y by O r t o n ( 1 9 2 5 ) .
t h e d e v e l o p m e n t o f two m o d e l s o f d y s l e x i a ,
d e f i c i t m o d el a n d t h e s e n s o r y d e f i c i t m o d e l .
As
i m p l i e d by t h e i r n a m e s , t h e s e tw o m o d e l s d i f f e r i n t e r m s o f t h e
•
presum ed l o c a t i o n o f t h e u n d e r l y i n g im p a irm e n t w i t h i n t h e v i s u a l
p ath w ay s i n v o lv e d i n t h e . r e a d i n g p r o c e s s .
A r e la t iv e ly p e rip h e ra l
i m p a i r m e n t i s a s s u m e d by t h e s e n s o r y d e f i c i t m odel w h e r e a s a
r e la tiv e ly c e n tra l
im p airm en t i s
a s s u m e d by t h e l i n g u i s t i c d e f i c i t
2
m o d el.
In o rd e r to d is c u s s th e s e m o d els, i t
i s n ec e ssa ry to b r ie f ly
re v ie w t h e s t r u c t u r e o f th e p rim a te v i s u a l sy stem .
F o llo w in g t h a t
r e v ie w , t h e m odels o f d y s l e x i a w i l l be d i s c u s s e d .
S in c e t h e e a r l y 19 5 0 ’ s
( e . g . , K u f f l e r , 19 5 3 ) , i t
h a s b e e n known
t h a t th e f i r i n g r a t e o f a g iv en s e n s o ry n euron w ith i n th e v is u a l
p ath w ay can be i n f l u e n c e d
( i . e . , in c re a s e d or d ecreased )
by
s t i m u l a t i o n o f a l i m i t e d a r e a a c r o s s t h e s u r f a c e o f. t h e r e t i n a ,
a re a r e f e r r e d to as th e r e c e p tiv e f i e l d
fie ld s
of th a t neuron.
an
R e c e p tiv e
and t h e i r c o r r e s p o n d i n g n e u r a l s u b s t r a t e s h av e been
c o n c e p tu a liz e d as " c h a n n e ls" t h a t f i l t e r
v a r y in g s tim u lu s d im en sio n s
1 9 78; M a f f e i ,
1978).
th e v is u a l sc e n e alo n g
( e . g . , B r a d d ick , C am p b ell, & A tk in so n ,
For e x a m p le, w ith r e s p e c t to s p a t i a l v i s i o n ,
larg e re c e p tiv e fie ld s
correspond to la rg e s p a t i a l
c h a n n e l s , w h ich
p ro v id e a c o a rs e n e u r a l r e p r e s e n t a ti o n
(i.e .,
v isu a l scene.
how ever, c o r re s p o n d t o s m a ll
S m all r e c e p t i v e f i e l d s ,
g lo b a l d e t a i l s )
s p a t i a l c h a n n e l s , w h ich p r o v i d e a f i n e n e u r a l r e p r e s e n t a t i o n
fin e or lo c a l d e ta ils ) ,
o f th e v is u a l sc e n e .
(i.e .,
D ep en d in g upon t h e i r
l o c a t i o n w ith in th e v is u a l sy stem , th e c h a r a c t e r i s t i c s
fie ld s
of th e
of re c e p tiv e
can v a ry a lo n g s e v e r a l o t h e r d im en sio n s as w e l l , su ch as
p re fe re n c e fo r c e r ta in shapes
faces),
( e .g . , sp o ts, lin e s ,
a n g les,
even
c o l o r s , and m o tio n .
For ex am p le, th e r e c e p t i v e f i e l d s
o f n e u r o n s a t t h e r e t i n a l an d
th a la m ic
(LGN) s t a g e s o f t h e p r i m a r y v i s u a l p a t h w a y a r e c i r c u l a r l y
shaped.
B ased on t h i s f i n d i n g ,
fe a tu re s of v isu a l s tim u li
encoded a t t h i s
sta g e .
it
has been p o s t u l a t e d t h a t sim p le
( e . g . , sp o ts of lig h t)
a r e e x t r a c t e d and
N eurons a t t h e c o r t i c a l s t a g e s ,
such as a re a s
3
Vl
(th e s t r i a t e
c o r t e x ) a n d V2, h a v e r e c e p t i v e f i e l d s
th a t are
e l o n g a t e d , w h ich s u g g e s t s t h a t t h e s e n e u r o n s e x t r a c t an d en co d e s u c h
s tim u lu s f e a t u r e s as l i n e s
(e .g .,
H ubei & W i e s e l , 1962; H ubei &
W ie s e l, 1965; Hubei & W ie s e l, 1 9 7 7 ).
F in a lly , th e re c e p tiv e f ie ld s
o f neurons lo c a te d a t th e h ig h e s t v is u a l c e n te r s ,
in fe ro te m p o ra l
(IT ) c o r te x ,
su ch a s th e
a r e s h a p e d l i k e h an d s an d f a c e s , w h ich
s u g g e s t s t h a t t h e s e n e u r o n s p e r f o r m c o m p le x t a s k s s u c h a s f a c e
re c o g n itio n
( e . g . , B ru c e , D esim one,
& G ross,
M i r a n d a , & Bender, 1 9 7 2 ; K e n d r i c k & B a l d w i n ,
have been i n t e r p r e t e d
(e .g .,
1981; G r o s s , R ocha^
1987).
These r e s u l t s
H ubei & W i e s e l , 1977) a s e v id e n c e f o r
th e id e a t h a t th e p r o c e s s in g o f v i s u a l in fo rm a tio n a lo n g th e p rim ary
p ath w ay i s - h i e r a r c h i c a l , s u c h t h a t t h e l a t t e r ,
m ore c o m p l e x , s t a g e s
a r e d e r i v e d from and d e p e n d e n t upon t h e f u n c t i o n i n g o f e a r l i e r
sta g e s.
I n a d d itio n to b ein g h i e r a r c h i c a l
i s a ls o o rg a n iz e d in p a r a l l e l :
s u s t a i n e d pathw ays
( s e e L en n ie,
in n a tu re ,
t h e p r im a r y p ath w ay
t h e r e a r e b o th t r a n s i e n t and
1 9 8 0 , f o r r e v i e w arid F i g u r e I ) .
The
t r a n s i e n t p ath w ay c o n s i s t s o f n e u r o n s w i t h r e l a t i v e l y l a r g e r e c e p t i v e
fie ld s
t h a t r e q u i r e b r i s k s t i m u l a t i o n f o r t h o s e n e u r o n s t o be
a c tiv a te d .
T h is p ath w ay o r i g i n a t e s i n t h e m a g n o c e l l u l a r l a y e r s o f
t h e LGN, p a s s e s t h r o u g h V I, n e x t t h e m i d d l e t e m p o r a l a r e a
te r m in a te s a t th e h ig h e r c o r t i c a l c e n te r s
(MT), a n d
(th e m ed ial s u p e r io r
t e m p o r a l a r e a ) b e l i e v e d t o be i n v o l v e d i n t h e i n i t i a t i o n o f s u c h
r e s p o n s e s a s e y e m o v e m e n ts .
I t i s h y p o th esize d t h a t t h i s
p a th w a y
d e t e c t s m o tio n a n d /o r h ig h te m p o ra l f r e q u e n c i e s w i t h i n th e v i s u a l
scene.
4
FIGURE I .
A Summary o f t h e H i e r a r c h y o f Many o f t h e
V i s u a l A r e a s i n t h e M ac aque Monkey ( a f t e r
Van E s s e n & M a u n s e l l , 1983)
5
The s u s t a i n e d p a t h w a y , o n t h e o t h e r h a n d , c o n s i s t s o f n e u r o n s
w ith sm all r e c e p t i v e f i e l d s
th a t re q u ire su sta in e d stim u la tio n fo r
t h o s e n e u r o n s t o be a c t i v a t e d .
T h is p athw ay o r i g i n a t e s i n th e
p a r o c e l l u l a r l a y e r s o f t h e LGN, p a s s e s t h r o u g h a r e a s V I , V4, a n d VP,
and te r m in a te s a t th e h ig h e r c o r t i c a l
c e n te rs
( e . g . , t h e IT ) b e l i e v e d
t o be i n s t r u m e n t a l i n form and p a t t e r n r e c o g n i t i o n
K e lly ,
1981; T o l h u r s t , 1973; W ils o n ,
( e . g . , B urbeck &
1 9 78).
The p r o c e s s o f r e a d i n g h a s b e e n c o n c e p t u a l i z e d a s a s e r i e s o f
v is u a l in fo rm a tio n p ro c e ssin g ta s k s .
These t a s k s b e g in a t th e low er
s t a g e s o f t h e p r im a r y v i s u a l p ath w ay and t e r m i n a t e a t t h e h i g h e r
c o rtic a l
c e n te rs
( e . g . , W e rn ick e’ s a r e a )
d e v o ted t o p r o c e s s in g th e
p h o n e t i c and s e m a n tic p r o p e r t i e s o f l i n g u i s t i c s t i m u l i
& D iL o llo ,
S ta n le y ,
1979; F i s h e r , 1980; G ibson & L e v in ,
1 9 8 1 ; W h y te , C u r r y ,
& H a le ,
( e . g . , A rn e tt
1975; H o w e ll, S m ith ,
&
19 8 5 ) .
W ith r e s p e c t t o t h e m o d e ls o f d y s l e x i a , t h e l i n g u i s t i c d e f i c i t
m odel a r g u e s t h a t d y s l e x i a i s
lin g u is tic
in to th e a p p ro p ria te l i n g u is t i c
1980; E l l i s ,
1981; E l l i s ,
S t e g e r , Kaman, & D e S e t t o , 1 9 7 5 ; V e l l u t i n o ,
19 7 7 ). U n f o r tu n a te ly ,
c o d e ( Bouma &
1984; K in s b o u rn e , 1986;
M cG u in n ess, 1985; V e l l u t i n o , 1977; V e l l u t i n o ,
N ile s,
of th e h ig h e r
c e n te rs to a d e q u a te ly reco d e th e sen so ry c h a r a c t e r i s t i c s
of v isu a l stim u li
L eg e in ,
th e r e s u l t of a f a i l u r e
th e r e s u l t s
1987; V e l l u t i n o ,
S t e g e r , M oyer, H a rd in g , &
of ex p erim en ts o s te n s ib ly
s u p p o r t i n g t h i s m odel h av e b e e n d e r i v e d from s t u d i e s whose v a l i d i t y
is
q u e stio n a b le
cases th re a ts
th e r e s u lt s
to
( e . g . , F le tc h e r & S a tz ,
in te rn a l v a lid ity
1 9 7 9 ) . F o r e x a m p l e , i n many
( e . g . , c e ilin g e f f e c ts ) render
of th e se s tu d ie s u n in te rp re ta b le .
T hus, t h e r e has
6
been l i t t l e
v a l i d s u p p o rt f o r t h i s m o d el.
T h e r e h a s b e e n much s u p p o r t f o r t h e o t h e r m o d el o f d y s l e x i a , t h e
s e n s o ry d e f i c i t m o d el.
T h is m odel a r g u e s t h a t d y s l e x i a i s th e r e s u l t
o f a f a i l u r e o f th e p e r i p h e r a l s t a g e s o f th e v i s u a l sy stem to p ro c e s s
and i n t e g r a t e s e q u e n t i a l v i s u a l i n f o r m a t i o n .
B e c a u s e t h e p ro b lem i n
d y s l e x i a i n v o l v e s t h e p e r c e p t i o n o f fo rm i n f o r m a t i o n
o f th e a lp h a b e t) i t
(e .g ., le tte rs
i s re a so n a b le to s p e c u la te th a t th e sensory
d e f i c i t w o u ld r e s i d e w i t h i n t h e s u s t a i n e d
(form 'p e r c e p t i o n )
p ath w a y .
The s e n s o r y d e f i c i t m o d e l i s t h e o n e b e i n g i n v e s t i g a t e d i n t h e
p re s e n t stu d y .
t h i s m odel i s
T hus, an in d e p th re v ie w o f t h e r e s e a r c h i n v e s t i g a t i n g
g iv e n belo w .
Some o f t h e e a r l i e s t r e s e a r c h i n v e s t i g a t i n g s e n s o r y d e f i c i t s
d y s l e x i a was p e r f o r m e d by S t a n l e y a n d H a l l
(1973).
To a s s e s s how
d y s le x ic and n o n d y s le x ic c h ild r e n p ro c e s s v i s u a l s t i m u l i ,
research ers
in
th ese
c o m p a r e d t h e p e r f o r m a n c e o f t h e two g r o u p s o n t a s k s
assum ed t o in d e x th e e a r l y s t a g e s o f v i s u a l in f o r m a t i o n p r o c e s s i n g .
The f i r s t
t a s k was a s e q u e n t i a l t h r e s h o l d t a s k i n w h i c h tw o p a r t s o f
a s t i m u l u s w e re e x p o s e d s e q u e n t i a l l y f o r 20 m sec w i t h t h e o n s e t o f
each a sy n c h ro n o u sly p re s e n te d
(i.e .,
a s p e c i f i e d tim e i n t e r v a l
e l a p s e d b e t w e e n t h e p r e s e n t a t i o n o f t h e f i r s t a n d t h e s e c o n d fo r m
p a rt).
T he s e c o n d t a s k was a m a s k i n g t a s k i n w h i c h t a r g e t s t i m u l i
( a l p h a b e t i c c h a r a c t e r s ) and m ask in g s t i m u l i
(v iz ., a s ta tic
r e c t a n g u l a r a r r a y o f d o t s ) w ere s e q u e n t i a l l y p r e s e n t e d a t v a r y in g
stim u lu s o n set a s y n c h ro n ie s.
S t a n l e y and H a ll fo u n d t h a t d y s l e x i c c h i l d r e n r e q u i r e d
s i g n i f i c a n t l y lo n g e r te m p o ra l i n t e r v a l s
th an n o n d y sle x ic c h ild re n
7
e i t h e r t o d i s t i n g u i s h s e q u e n t i a l p r e s e n t a t i o n s fr o m s i m u l t a n e o u s
p re se n ta tio n s
(s e q u e n tia l th re s h o ld ta s k ) o r to c o r r e c tl y i d e n t i f y
t h e a l p h a b e t i c c h a r a c t e r p r e s e n t e d when t h e m ask f o l l o w e d t h e
c h a r a c t e r i n tim e
(m ask in g t a s k ) .
B ased on t h e s e f i n d i n g s , th e y
co n c lu d e d t h a t t h e r e a r e s i g n i f i c a n t
d i f f e r e n c e s i n how d y s l e x i c s
v e r s u s n o rm als p ro c e s s v i s u a l i n f o r m a t i o n :
p e rsists
v is u a l in fo rm a tio n
l o n g e r and i s p r o c e s s e d s lo w e r f o r th e d y s l e x i c s .
A d d itio n al su p p o rt fo r t h i s
c o n c l u s i o n h a s come f r o m s t u d i e s
t h a t have i n v e s t i g a t e d th e p r o c e s s in g o f v is u a l in fo rm a tio n in
d y s l e x i c s and n o rm a ls em p lo y in g a v a r i e t y o f s t i m u l u s p a r a m e te r s and
e x p e rim en tal ta s k s .
A ll s t u d i e s fo u n d t h a t d y s le x ic s r e q u ir e d
s i g n i f i c a n t l y lo n g e r tem p o ra l i n t e r v a l s th a n d id n o rm als i n o rd e r to
p erform th e e x p e rim e n ta l ta s k s .
stim u li
n o n lin g u istic
( B adcock & L o v e g r o v e , 1981; L o v e g ro v e , M ed d le, & S l a g h u i s ,
1980; S t a n l e y ,
M c In ty re ,
19 7 5 ) , l i n g u i s t i c s t i m u l i
1 9 8 3 ; L o v e g r o v e & B row n,
l o c a t i o n s and o r i e n t a t i o n s
1 9 7 8 ; O’ N e i l l & S t a n l e y ,
id e n tific a tio n
Goyen,
T h i s was t r u e f o r :
ta sk s
1 9 7 8 ), s tim u li of v a ry in g s p a t i a l
( e . g . , L ovegrove, B i ll i n g ,
1 97.6), a n d f o r r e c o g n i t i o n ,
19 8 5 ).
in d ic a te th a t, r e la tiv e
(i.e .,
in sp e c tio n ,
and
Taken t o g e t h e r , th e r e s u l t s o f
have p o o re r tem p o ra l a c u i t y , t h a t i s ,
p e rsiste n c e
& S la g h u is,
( e . g . , G ro ssh G le n n & R o th e n b e rg 1984; L y le &
1 9 7 5 ; W hyte e t a l . ,
th ese s tu d ie s
(D iL o llo , H anson, &
t o n o rm als, d y s l e x i c c h ild r e n
lo n g er d u ra tio n s of v isu a l
th e r e p r e s e n t a t i o n o f a s tim u lu s re m a in s w ith in
t h e v i s u a l s y s t e m f o r an e x t e n d e d l e n g t h o f t i m e ) f o r b o t h l i n g u i s t i c
and n o n l i n g u i s t i c s t i m u l i .
What a r e t h e t h e o r e t i c a l i m p l i c a t i o n s o f t h e f i n d i n g t h a t
8
d y s l e x i c s have lo n g e r th a n norm al d u r a t i o n s o f v i s u a l p e r s i s t e n c e ?
D i L o l l o , H anson, and M c In ty re
q u estio n .
( 1 9 8 3 ) p r o p o s e d an a n s w e r t o t h i s
T hey b e l i e v e t h a t d y s l e x i c i n d i v i d u a l s n o t o n l y p r o c e s s
v i s u a l in fo rm a tio n a t a slo w er r a t e , b u t a ls o t h a t th e y r e q u ir e a
l o n g e r p e r i o d o f tim e t o r e c o v e r from v i s u a l s t i m u l a t i o n
lo n g er r e f r a c to r y p e rio d ).
And a l e n g t h y r e f r a c t o r y
(i.e .,
a
p e r i o d w o u ld
seem t o be d e t r i m e n t a l i n t h o s e c i r c u m s t a n c e s i n w h i c h v i s u a l s t i m u l i
a re s e q u e n tia l in n a tu re
( e .g ., re a d in g ).
T h is i s
because th e
e x is te n c e o f a r e f r a c t o r y p e rio d d u rin g th e p ro c e ssin g o f v is u a l
i n f o r m a t i o n w o u ld p r e c l u d e t h e p r o c e s s i n g o f a n y a d d i t i o n a l
s tim u la tio n d u rin g t h a t p e r io d , t h a t i s ,
any a d d i t i o n a l in fo rm a tio n
w h ich e n t e r e d t h e v i s u a l s y s te m d u r i n g t h e r e f r a c t o r y
p e r i o d w o u ld b e
degraded.
' The s p e c i f i c s t i m u l u s a t t r i b u t e s
on t h e p a r t i c u l a r p r o c e s s i n g s t a g e i n
t h a t w o u ld be d e g r a d e d d e p e n d
q u estio n .
S in c e th e
d e g r a d a t i o n p r o b a b ly o c c u r s a t an e a r l y s t a g e o f p r o c e s s i n g , th e
p h y sical a ttr ib u te s
o f t h e s t i m u l i w o u l d be a f f e c t e d .
T h is,
in- t u r n ,
s h o u ld l i m i t th e p e rfo rm a n c e o f t h e s y s te m a t t h e h i g h e r s t a g e s w here
such p r o p e r tie s as th e s t r u c t u r a l a n d /o r c o g n itiv e
s tim u li a re pro cessed .
c o m p o n e n ts o f
W i t h i n t h e p r e s e n t c o n t e x t , a c h i l d who i s
u n ab le to a d e q u a te ly p ro c e ss s e q u e n tia l p r e s e n ta tio n s o f v is u a l
s t i m u l i w o u ld n o t be a b l e t o r e a d w e l l .
It
i s im p o r ta n t t o n o te t h a t a d e v e lo p m e n ta l t r e n d to w a rd norm al
v is u a l p ro c essin g in d y sle x ic s i s
stu d ie s
a p p a re n t in th e r e s u l t s
o f some
( e . g . , Badcock & L o v e g r o v e , 1981; D iL o llo , H an so n , &
M c In ty re ,
19 8 3 ; L o v e g r o v e & B row n,
1978; L y le & Goyen, 1975; O 'N e i l l
9
& S t a n l e y , 1976).
S p e c ific a lly ,
in s e p a r a tio n th r e s h o ld p arad ig m s,
t h e t e m p o r a l , s e p a r a t i o n r e q u i r e d by d y s l e x i c c h i l d r e n t o p e r f o r m
ce rta in
e x p e rim e n ta l ta s k s d e c re a s e d s i g n i f i c a n t l y as t h e i r ages
i n c r e a s e d f r o m 8 t o 14 y e a r s .
T h is f in d in g has been i n t e r p r e t e d as
e v id e n c e t h a t th e d ev e lo p m e n t o f th e v i s u a l sy stem i n d y s l e x i c s i s
d e la y e d r e l a t i v e to n o rm als.
T h i s h a s l e d some r e s e a r c h e r s
d e fic its
to propose t h a t th e se n so ry
e x h i b i t e d by y o u n g d y s l e x i c s w i l l ,
in a l l lik e lih o o d ,
d i s a p p e a r by t h e t i m e t h e s e c h i l d r e n r e a c h a d u l t h o o d .
s e e m s t o be c o u n t e r i n t u i t i v e ,
T h is p ro p o sa l
how ever, as r e s e a r c h t h a t has
i n v e s t i g a t e d th e l i t e r a c y s k i l l s o f a d u l t d y s l e x i c s h as fo u n d t h a t
n e i t h e r a d o l e s c e n t n o r a d u l t d y s l e x i c s o u tg ro w t h e i r p ro b le m s,
a l t h o u g h s i g n i f i c a n t g a i n s a r e made by some i n d i v i d u a l s
1970; F in u c c i,
S carborough,
1985; M ile s ,
1984; S to n e ,
1986; F e r r e i r a ,
1980).
Thus,
it
19 8 4 ; Raw son,- 1 9 6 8 ;
se e m s v e r y l i k e l y t h a t
d y s l e x i a does p e r s i s t beyond t h e c h ild h o o d y e a r s .
h o w e v e r , w h e t h e r t h e sam e s e n s o r y d e f i c i t s
(C ritc h le y ,
It
i s n o t known,
assum ed t o u n d e r l i e
ch ild h o o d d y s le x ia a r e r e s p o n s ib le f o r d y s le x ia in ad u lth o o d s in c e
te m p o ra l p r o c e s s in g i n a d u l t d y s l e x i c s h as n o t been i n v e s t i g a t e d .
To p e r f o r m t h a t i n v e s t i g a t i o n ,
th is
s t u d y ex am in ed w h e th e r a d u l t
d y s l e x i c s d e m o n s t r a t e p r o b l e m s i n t h e t e m p o r a l i n t e g r a t i o n o f fo rm
i n f o r m a t i o n s i m i l a r t o th e p ro b lem s d e m o n s tra te d i n c h i l d d y s l e x i c s .
To do s o , t h i s s t u d y e m p lo y e d a n e x p e r i m e n t a l p a r a d i g m t h a t p l a c e d
dem ands o n t h e a d u l t s u b j e c t ' s a b i l i t y t o i n t e g r a t e v i s u a l fo r m
in fo rm a tio n over tim e .
M c F a r la n d
T h i s p a r a d i g m was o r i g i n a l l y d e v e l o p e d by
( 1 9 6 5 ) a n d r e f i n e d by S h o n t z
(1968).
In b r i e f ,
it
in v o lv e d
r
10
p r e s e n t i n g s i d e o r a n g l e p a r t s o f a v i s u a l form e i t h e r s e q u e n t i a l l y
(i.e .,
a s p e c i f i e d te m p o ra l i n t e r v a l e la p s e d b etw een t h e p r e s e n t a t i o n
o f e a c h fo rm p a r t ) o r s i m u l t a n e o u s l y
(i.e .,
a p p e a r e d a t t h e sam e t i m e ) t o e a c h s u b j e c t .
to ju d g e i f
a ll
o f th e form p a r t s
The s u b j e c t ’ s t a s k was
th e form p a r t s w ere s i m u l t a n e o u s , o v e r l a p p i n g , o r
s u c c e s s iv e in tim e .
B eca u se t h e s t i m u l i w ere p r e s e n t e d f o v e a l l y and
b e c a u s e t h e s u b j e c t ' s r e s p o n s e was b a s e d o n p e r c e p t i o n o f f o r m , i t
is
l i k e l y t h a t th e s e p ro c e d u re s tap p ed th e re sp o n se p r o p e r t ie s o f th e
s u s t a i n e d p ath w ay .
S h o n t z ( 1 9 6 8 ) e x p a n d e d u p o n t h i s p a r a d i g m by i n v e s t i g a t i n g ,
a d d itio n to fo rm -p art c o n fig u ra tio n ,
(i.e .,
in
th e a f f e c t th a t c o n tig u ity ,
t h e o r d e r o f s e q u e n c in g o f form p a r t s ) h a s on te m p o r a l
in te g ra tio n .
H i s f i n d i n g s r e v e a l e d t h a t f o r m - p a r t c o n f i g u r a t i o n w as
t h e o n l y f a c t o r s i g n i f i c a n t l y a f f e c t i n g t e m p o r a l I n t e g r a t i o n ..
E m p l o y in g a p a r a d i g m s i m i l a r t o t h e o n e d e s c r i b e d a b o v e , t h e
p r e s e n t e x p e rim e n t com pared d y s l e x i c a d u l t s '
a b ility to in te g ra te
v i s u a l form i n f o r m a t i o n o v e r tim e t o t h a t o f n o r m a ls .
s e q u e n c i n g was i n v e s t i g a t e d .
S e n s itiv ity to
P o o rer s e n s i t i v i t y o f a d u lt d y s le x ic s
t o s e q u e n t i a l f o r m i n f o r m a t i o n , r e l a t i v e t o n o r m a l s , w as t h e e x p e c t e d
re su lt.
METHOD
S u b je c ts
(6 m a l e s a n d 2 f e m a l e s ) who w e re d i a g n o s e d a s
E ig h t a d u lts
d y s l e x i c by t h e R e s o u r c e C e n t e r o f M o n ta n a S t a t e U n i v e r s i t y w e re p a i d
to p a r t i c i p a t e in th e s tu d y .
In a d d itio n ,
e ig h t n o n d y slex ic a d u lts
(6 m a l e s and 2 f e m a l e s ) w e re a l s o p a i d t o p a r t i c i p a t e .
The a g e s o f
t h e s u b j e c t s r a n g e d fr o m 18 t o 37 y e a r s .
In a d d itio n to
b e i n g e n r o l l e d a t M o n ta n a S t a t e U n i v e r s i t y , a l l
v o l u n t e e r s h a d t o m e e t t h e f o l l o w i n g c r i t e r i a i n o r d e r t o be a c c e p t e d
as s u b j e c t s :
(a) n a t i v e s p e a k e rs o f E n g lis h ;
to rn o rm al v is io n ;
d isa b ilitie s.
(b) norm al o r c o r r e c te d
and (c ) f r e e o f any p h y s i c a l , m e n t a l , o r e m o tio n a l
D u rin g th e t r a i n i n g
p e r i o d , o n e d y s l e x i c m a l e was
e x c l u d e d fro m t h e s t u d y b e c a u s e he d i d n o t h a v e c o r r e c t e d t o n o r m a l
v isio n .
A p p a r a tu s and S t i m u l i
A Z -80 m i c r o c o m p u t e r b r e a d b o a r d , d e s i g n e d a n d b u i l t u s i n g
c o n v e n tio n a l e l e c t r o n i c s ,
g e n e r a te d and d is p la y e d th e v i s u a l s tim u lu s
o n a T e k t r o n i x 2 2 1 3A o s c i l l o s c o p e
(P31 p h o s p h o r ) .
The s t i m u l u s was a
lu m in o u s o u t l i n e s q u a r e s u b t e n d i n g a v i s u a l a n g le o f I a r c deg a t t h e
eye.
P rocedure
Two l e v e l s . o f f o r m - p a r t c o n f i g u r a t i o n
fa c to ria lly
( s i d e s v s . a n g l e s ) w e re
c o m b in e d w i t h tw o l e v e l s o f c o n t i g u i t y
(c o n tig u o u s v s .
12
n o n c o n t i g u o u s ) w h ich r e s u l t e d
co n d itio n s
(see F ig u re 2 ):
in th e fo llo w in g fo u r ex p erim en tal
s id e s - c o n tig u o u s , s id e s -n o n c o n tig u o u s ,
a n g l e s —c o n t i g u o u s , a n d a n g l e s —n o n c o n t i g u o u s .
A ll fo u r c o n d itio n s
w ere ran d o m ly p r e s e n t e d t o t h e d y s l e x i c and norm al s u b j e c t s .
E a c h s u b j e c t was g r e e t e d by t h e e x p e r i m e n t e r who e x p l a i n e d t h e
g e n e r a l p u r p o s e o f t h e s t u d y a n d o b t a i n e d i n f o r m e d c o n s e n t . Once
c o n s e n t was g i v e n , t h e s u b j e c t was s e a t e d i n t h e d i m l y l i t
v isio n
l a b o r a t o r y a t a d i s t a n c e o f 65 cm away f r o m t h e o s c i l l o s c o p e s c r e e n .
As t h e s u b j e c t d a r k a d a p t e d , t h e e x p e r i m e n t e r r e a d t h e i n s t r u c t i o n s
w h ich d e t a i l e d t h e e x p e r i m e n t a l p r o c e d u r e s and t a s k s
( s e e A p p e n d ix ).
A l t h o u g h t h e o c c u r r e n c e o f e y e m ov em en ts was u n l i k e l y s i n c e t h e
d u ra tio n s of exposure used in th e stu d y
(e .g .,
41 m s e c ) f e l l w e l l
w ith in th e la te n c y r e q u ir e d f o r th e e x e c u tio n o f s a c c a d ic or vergence
e y e m ov em en ts ( e . g . , 160 m s e c ) , e a c h s u b j e c t was t r a i n e d o n t h e
e ffe c ts
o f e y e m ovem ent a n d t o l d t o r e f r a i n fr o m i n i t i a t i n g
m ov em en ts d u r i n g a n y o f t h e e x p e r i m e n t a l t r i a l s .
ey e
A ll s u b je c ts
co m p lied w ith t h i s r e q u e s t .
N e x t , t h e s u b j e c t p e r f o r m e d a b r i g h t n e s s m a t c h i n g t a s k i n w h ic h
th e p e rceiv ed b rig h tn e s s of sq u ares p re se n te d under each of th e fo u r
c o n d i t i o n s w e re e q u a t e d .
The s t i m u l u s - o n - t i m e was 2 m s e c , t h e I P I
was 12 m s e c , a n d t h e p r e s e n t a t i o n mode a l t e r n a t e d
and s i m u l t a n e o u s .
be b r i g h t e r ,
b etw e en s e q u e n t i a l
The s u b j e c t s t a t e d w h e t h e r t h e s q u a r e s a p p e a r e d t o
d im m e r, o r e q u a l o v e r t r i a l s .
The p u r p o s e o f t h i s t a s k
was t o i n s u r e t h a t p e r f o r m a n c e d u r i n g f o r m a l d a t a c o l l e c t i o n was
b a s e d o n t e m p o r a l c u e s o n l y a n d n o t on v a r i a t i o n i n b r i g h t n e s s t h a t
FIGURE 2.
Illustration of Experimental Conditions
"SID E" PARTS
"ANGLE" PARTS
3
4
3
I
2
2
I
I
O rd e r o f S e q u e n c in g :
1 .2 .3 .4
(S id es-C o n tig u o u s)
1 . 3 .2 .4
(S id e s-N o n c o n tig u o u s)
O rd er o f S e q u e n c in g :
1 ,2 ,3 ,
(A n g le s-C o n tig u o u s)
1 ,3 ,2 ,
(A n g le s-N o n co n tig u o u s)
m ig h t co v a r y w ith th e e x p e rim e n ta l m a n ip u la tio n s .
A ll su b je c ts
j u d g e d t h e s t i m u l i t o be e q u a l l y b r i g h t , i n d i c a t i n g t h a t no a p p a r e n t
b r i g h t n e s s c u e s w e re p r e s e n t f o r t h e s t i m u l i u s e d .
Upon c o m p l e t i o n o f t h e b r i g h t n e s s m a t c h i n g t a s k ,
th e
e x p e r i m e n t a l p r o c e d u r e s w e re e x p l a i n e d t o e a c h s u b j e c t .
The s u b j e c t
was t o l d t h a t s / h e w o u ld be shown p a r t s o f a s q u a r e p r e s e n t e d e i t h e r
s i m u l t a n e o u s l y , i n w h i c h t h e fo r m p a r t s o f t h e s q u a r e w e r e p r e s e n t e d
a t t h e sam e t i m e , o r s e q u e n t i a l l y ,
asy n c h ro n o u sly p re s e n te d .
in te rv a l,
i n w h i c h e a c h f o r m p a r t was
In th e l a t t e r
c a s e , a s p e c i f i e d tim e
known a s t h e i n t e r p a r t i n t e r v a l
( I P I ) , e l a p s e d b etw een t h e
o f f s e t and t h e o n s e t o f th e v a r i o u s form p a r t s .
o r d e r was r a n d o m l y d e t e r m i n e d o v e r t r i a l s
occurred e q u a lly ).
The p r e s e n t a t i o n
(b o th ty p e s o f p r e s e n ta tio n
The s u b j e c t was t o l d t h a t t h e t a s k was t o d e c i d e
w h e th e r t h e form p a r t s o f t h e s q u a r e w ere p r e s e n t e d s e q u e n t i a l l y o r
s im u lta n e o u s ly on each t r i a l .
s e n s itiv ity
In o r d e r t o o b ta in a m easure o f
to seq u en cin g f r e e of re s p o n s e or c r i t e r i o n
b ia s , each
s u b j e c t was a s k e d t o r a t e t h e c o n f i d e n c e o f t h a t d e c i s i o n , u s i n g a
s ix c a te g o ry r a t i n g s c a le :
su re;
" I" , se q u e n tia l,
se q u e n tia l,
fa irly
"3", s e q u e n tia l,
guess;
"5",
sim u lta n e o u s, f a i r l y s u re ;
su re.
F in a lly ,
very su re ;
guess;
"2" ,
"4 ” , s im u lta n e o u s,
and " 6" , s i m u l t a n e o u s , v e ry
e a c h s u b j e c t was i n s t r u c t e d t o d e v e l o p a s e t o f
p erc e p tu a l c r i t e r i a fo r d if f e r e n tia tin g
b e t w e e n s e q u e n t i a l and
s i m u l t a n e o u s p r e s e n t a t i o n s o f t h e . s q u a r e and t o u s e t h e s e c r i t e r i a
th ro u g h o u t d a ta c o lle c tio n .
F o r m a l t r a i n i n g o f t h e s u b j e c t s on t h e e x p e r i m e n t a l t a s k
o c c u r r e d d u r i n g t h e f i r s t tw o s e s s i o n s .
The p u r p o s e o f t r a i n i n g was
15
tw o fo ld :
(I)
to s t a b i l i z e
ea c h s u b j e c t ’ s p e rfo rm a n c e and ( 2 ) to
d e te r m in e t h e IP I v a lu e a t w hich e a c h s u b j e c t a c c u r a t e l y
d i s c r i m i n a t e d s e q u e n t i a l fr o m s i m u l t a n e o u s p r e s e n t a t i o n o f t h e fo rm
70% o f t h e t i m e f o r t h e s i d e s - c o n t i g u o u s c o n d i t i o n .
referred
T h i s w i l l be
to as th e IP I th r e s h o l d .
T ra in in g c o n s is te d of p re s e n tin g th e sid e s-c o n tig u o u s
e x p e r i m e n t a l c o n d i t i o n t o e a c h s u b j e c t f o r s i x b l o c k s o f 50 t r i a l s
each p er t r a i n i n g s e s s io n .
Each t r i a l
began w ith a s im u lta n e o u s
w a r n i n g " b e e p " and p l o t t i n g o f a f i x a t i o n
p o in t.
One s e c o n d l a t e r ,
t h e s q u a r e was d i s p l a y e d a n d t h e s u b j e c t g a v e h i s / h e r r e s p o n s e .
Four
s e c o n d s l a t e r , t h e b e e p s o u n d e d a g a i n a n d t h e f i x a t i o n p o i n t was o n c e
a g a in p l o t te d ,
in d i c a t i n g th e b e g in n in g of a n o th e r t r i a l .
Feedback
was g i v e n t h r o u g h o u t t r a i n i n g .
T hree s e s s i o n s o f fo rm a l d a ta c o l l e c t i o n fo llo w e d th e t r a i n i n g
se ssio n s.
For th e s e s e s s io n s ,
th e IP I th r e s h o ld e s ta b lis h e d f o r th e
s i d e s - c o n t i g u o u s c o n d i t i o n d u r i n g p r a c t i c e was u s e d d u r i n g
p r e s e n ta tio n of th e fo u r e x p e rim en tal c o n d itio n s.
co n sta n t,
vary.
By h o l d i n g I P I
a c r o s s c o n d i t i o n s , r e c o g n i t i o n p e r f o r m a n c e was a l l o w e d t o
A l l f o u r e x p e r i m e n t a l c o n d i t i o n s w e re p r e s e n t e d i n two
c o n s e c u tiv e b l o c k s , w ith a tw o -m in u te r e s t p e rio d p ro v id e d a f t e r th e
first
b lo c k and a f i v e - m i n u t e r e s t p e r io d p ro v id e d a f t e r t h e seco n d
b lo ck .
T h u s , d a t a c o l l e c t i o n i n v o l v e d e i g h t b l o c k s o f 50 t r i a l s
f o r a t o t a l o f 400 t r i a l s
per se ssio n
( 1 00 t r i a l s
each
per c o n d itio n ).
The o r d e r o f p r e s e n t a t i o n o f e a c h c o n d i t i o n was d e t e r m i n e d r a n d o m l y .
No f e e d b a c k was g i v e n d u r i n g t h e s e s s i o n s .
F in a lly ,
e a c h s u b j e c t was q u e s t i o n e d ,
d e b rie fe d ,
a n d p a i d by t h e
16
e x p e r i m e n t e r when a l l f i v e s e s s i o n s h a d b e e n c o m p l e t e d .
17
RESULTS
B e fo re t h e d a t a w ere s t a t i s t i c a l l y
an a ly z e d f o r r e l i a b i l i t y ,
th e
p e r c e n t d is c r im in a tio n d a ta o b ta in e d fo r each s u b je c t under each o f
t h e e x p e r i m e n t a l c o n d i t i o n s w ere t r a n s f o r m e d i n t o h i t and f a l s e a la r m
r a t e s a n d t h e n p l o t t e d a g a i n s t o ne a n o t h e r on r e c e i v e r —o p e r a t i n g c h a ra c te ris tic
(ROC) c u r v e s u s i n g d o u b l e p r o b a b i l i t y a x e s
(G r e e n &
S w e t s , 19 6 6 ) .
T h i s was d o n e i n o r d e r t o d e t e r m i n e w h e t h e r t h e
assu m p tio n s n e c e s s a r y f o r th e u se o f p a ra m e tric s e n s i t i v i t y m easures
(e .g .,
d * ) w ere m e t.
I n s p e c t i o n o f t h e ROC c u r v e s r e v e a l e d t h a t t h e
a s s u m p tio n s w ere n o t m et.
m easure o f s e n s i t i v i t y ,
T h erefo re,
an u n b i a s e d n o n p a r a m e t r i c
t h e a r e a u n d e r t h e ROC c u r v e P ( A ) , was
c a l c u l a t e d and an a r c s i n tr a n s f o r m a t i o n p erform ed
(McNic o l ,
1972).
F o u r a r e a v a l u e s , o n e f o r e a ch c o n d i t i o n , w ere c a l c u l a t e d f o r each
s u b j e c t f o r a t o t a l o f 60 a r e a v a l u e s .
A 2 x 2 x 2 th re e -w a y A n a ly s is o f V a rian ce
(ANOVA) f o r s p i l t
p l o t d e s i g n s was c a l c u l a t e d o n t h e s e n s i t i v i t y d a t a
(s e e T ab le I ) .
T h i s a n a l y s i s r e v e a l e d t h a t s e n s i t i v i t y t o s e q u e n c i n g was n o t
s ig n if ic a n tly a ffe c te d
by d i s a b i l i t y
d y s l e x i c s a n d n o r m a l s was e q u i v a l e n t .
s ig n ific a n tly a ffe c te d
(F < 1 . 0 ) .
T he s e n s i t i v i t y o f
H o w e v e r, s e n s i t i v i t y was
by c o n f i g u r a t i o n , F ( 1 ,
13) = 1 7 . 0 8 0 , p < . 0 0 5 .
A l l s u b j e c t s , r e g a r d l e s s o f c l a s s i f i c a t i o n , w e r e m o re s e n s i t i v e t o
seq u e n cin g w ith a n g le p a r t s th a n w ith s id e p a r t s .
re lia b ly
a f f e c t e d by c o n t i g u i t y ,
F ( I , 13) = 1 5 . 0 0 0 ,
S e n s i t i v i t y was
p < .0 0 5 .
18
S e n s i t i v i t y was g r e a t e r w i t h c o n t i g u o u s p r e s e n t a t i o n s
th an w ith
n o n co n tig u o u s p r e s e n t a t i o n s .
stu d y ,
M ost i m p o r t a n t f o r t h i s
re v e a le d a s ig n if ic a n t in te r a c tio n
F ( 1 , 13) = 7 0 .0 0 0 ,
p < .0 0 1 .
b etw een c o n t i g u i t y and d i s a b i l i t y ,
H e r e , n o r m a l s w e r e m o re s e n s i t i v e t o
se q u e n cin g w ith c o n tig u o u s p r e s e n ta tio n s r e l a t i v e
p r e s e n t a t i o n s , w hereas d y s le x ic s d id n o t d i f f e r
co n d itio n s.
in te ra c tio n
p < .0 0 1 .
And f i n a l l y ,
a n a ly sis
to n o n co n tig u o u s
b e t w e e n t h e tw o
th e a n a ly s is a ls o re v e a le d a s ig n if ic a n t
b etw e en c o n f i g u r a t i o n and c o n t i g u i t y ,
F ( I , 13) = 1 0 5 .9 3 0 ,
S e n s i t i v i t y was g r e a t e r u n d e r t h e n o n c o n t i g u o u s c o n d i t i o n
when a n g l e s w e r e u s e d , h o w e v e r , i t
was g r e a t e r u n d e r t h e
co n tig u o u s
c o n d i t i o n when s i d e s w e r e u s e d .
T ab le I .
A n a l y s i s o f V a r i a n c e C o m p u te d o n t h e A r e a U n d e r t h e ROC
C urve a s a M ea su re o f S e n s i t i v i t y t o S e q u e n c in g .
S ource
B e tw e e n
D isa b ility
erro r
SS
(D)
3 .4 0 0
W ith in
C o n fig u ratio n
D xC
erro r
C o n tig u ity
D x CO
erro r
3.660
0.260
(C)
(CO)
C x CO
D x C x CO
erro r
* p < .0 0 5
** p < .001
2 .6 1 1
1 .2 3 0
0.002
0 .9 3 8
0.030
0 .1 4 0
0.020
0.220
0 .0 0 4
0 .0 2 7
df
14
I
13
35
I
I
13
I
I
13
. I
I
13
MS
0 .260
0.262
—
I .230
0.002
0 .0 7 2
F
0 .9 9 2
—
—
17. 080*
0 .0 2 8
0.030
1 5 .0 0 0 *
0 .140
7 0 . 0 0 0 **
0.0 0 2
0.220
0 .0 0 4
0 .0 0 2
1 0 5 .9 3 0 * *
1 .9 3 0
—
By a v e r a g i n g t h e c u m u l a t i v e P (A ) d a t a o f t h e n o r m a l s u b j e c t s
( s e e F ig u r e 3) and t h e d y s l e x i c s u b j e c t s
( s e e F ig u r e 4) w i t h i n
19
co n d itio n s,
t h e o v e r a l l e f f e c t s o f t h e e x p e r i m e n t a l c o n d i t i o n s on
s e n s i t i v i t y t o s e q u e n c i n g a r e su m m arized i n p i c t o r i a l fo rm .
A verage R e c e i v e r - O p e r a t i n g - C h a r a c t e r i s t i c
f o r th e E x p e rim e n ta l C o n d itio n s
(ROC) C u r v e s o f N o n d y s l e x i c s
P(SEQISEQ)
FIGURE 3 .
S id e s -C o n tig u o u s
S id e s-N o n c o n tig u o u s
A n g les-C o n tig u o u s
A n g les-N o n co n tig u o u s
P(SEQiSIM)
A verage R e c e i v e r - O p e r a t i n g - C h a r a c t e r i s i t c
f o r th e E x p e rim e n ta l C o n d itio n s
(ROC) C u r v e s o f D y s l e x i c s
P(SEQtSEQ)
FIGURE 4 .
S id e s-C o n tig u o u s
S id e s-N o n c o n tig u o u s
A n g les-C o n tig uous
A n g les-N o n co n tig u o u s
P(SEQt SIM)
22
DISCUSSION
.
The p r i n c i p l e r e s u l t o f t h i s
stu d y i s
th a t th e s e n s i t i v i t y of
t h e n o r m a l s t o s e q u e n t i a l fo r m i n f o r m a t i o n i s s u p e r i o r t o t h a t o f
* d y s l e x i c s when p a r t s o f a s t i m u l u s a r e p r e s e n t e d c o n t i g u o u s l y .
The
n o r m a l s a r e a b l e t o d i s c r i m i n a t e s e q u e n t i a l from, s i m u l t a n e o u s
p re sen tatio n s at b rie fe r
d u ra tio n s
th a n can th e d y s l e x i c s .
T h is
r e s u l t im p lie s t h a t , u n d er th e s e c o n d i t i o n s , te m p o ra l p r o c e s s in g o f
form i n f o r m a t i o n i s s lo w e r w i t h i n t h e v i s u a l sy s te m s o f d y s l e x i c s ,
or
i n o t h e r w o rd s, f o r d y s l e x i c s , fo rm in f o r m a t i o n p e r s i s t s l o n g e r
(i.e .,
p o o re r tem p o ra l a c u i t y ) .
What i s
th e e x p la n a tio n f o r th e s e r e s u l t s ?
I t may be a r g u e d ,
f o r e x a m p le , t h a t th e d i f f e r e n c e s b etw een d y s l e x i c s and n o rm a ls u n d er
t h e s e c o n d i t i o n s c o u l d be t h e r e s u l t o f s a m p l i n g , r e s p o n s e , o r
c rite rio n
b iases.
The p o s s i b i l i t y o f s a m p l i n g b i a s i s r u l e d o u t ,
h o w e v e r , b e c a u s e t h e sam e s u b j e c t s w e r e u s e d u n d e r a l l
e x p e rim en tal c o n d itio n s .
The p o s s i b i l i t y t h a t t h e s e d i f f e r e n c e s a r e
d ue t o r e s p o n s e o r c r i t e r i o n b i a s e s i s
a v e r a g e m iss and f a l s e
fo u r
a ls o r u le d o u t s i n c e . th e
a l a r m r a t e s w e r e co m p ared u s i n g t h e Mann-
W h i t n e y U T e s t a n d no s i g n i f i c a n t d i f f e r e n c e s w e re f o u n d .
The m ost l i k e l y e x p l a n a t i o n i s
t h a t a tem p o ra l i n t e g r a t i o n
d e f i c i t e x i s t s w i t h i n t h e v i s u a l pathw ay o f th e a d u l t d y s l e x i c s .
th is
In
v i e w , s l o w e r p r o c e s s i n g o f f o r m i n f o r m a t i o n w o u ld m ean t h a t t h e
n e u r a l r e p r e s e n t a t i o n o f s u c c e s s iv e s t i m u l i . sh o u ld p e r c e p t u a l l y
23
o v e r la p i n tim e .
In th e p re s e n t stu d y , th e re p r e s e n ta tio n of
s e q u e n t i a l fo rm p a r t s o v e r l a p p e d i n t h e v i s u a l s y s t e m s o f t h e
d y s l e x i o s , a n d c o n s e q u e n t l y , t h e s e r e p r e s e n t a t i o n s w e re m ore o f t e n
p e rc e iv e d as sim u lta n e o u s r a t h e r th a n s e q u e n tia l.
One c o n s e q u e n c e o f h a v i n g t e m p o r a l o v e r l a p o f r e p r e s e n t a t i o n s i s
th a t th e c h a r a c t e r i s t i c s
of th o se r e p re s e n ta tio n s
e t c . ) w o u l d be d e g r a d e d :
in o th e r w ords, each r e p r e s e n t a t i o n o f a
g i v e n s t i m u l u s w o u ld i n t e r f e r e w i t h o n e a n o t h e r .
(i.e .,
s iz e , shape,
T h is id e a i s
s i m i l a r t o t h e e x p l a n a t i o n p r o p o s e d f o r s u c h phenom ena a s v i s u a l
m ask in g
( e . g . , Fox,
1 9 7 8 ; Kahnm an, I 9 6 8 ) .
I n m ask in g , th e p re s e n c e
o f .one s t i m u l u s , t h e m a s k , i m p a i r s t h e v i s i b i l i t y o f a s e c o n d
s t i m u l u s , t h e t a r g e t , when b o t h o c c u r c l o s e l y c o u p l e d i n t i m e .
im p airm en t i s
The
p re s u m a b ly due t o i n t e r f e r e n c e b etw een t h e n e u r a l
r e p r e s e n t a t i o n s o f t a r g e t and m a s k .'
I n te rm s o f d y s l e x i a ,
th is
te n d e n c y f o r p e r c e p t u a l o v e r la p and
i n t e r f e r e n c e w o u ld a p p l y t o t h e p r o c e s s i n g o f a l p h a b e t i c a n d
lin g u is tic stim u li,
such as l e t t e r s .
p h y sic a l a t t r i b u t e s
o f a l p h a b e t i c s t i m u l i w o u ld r e s u l t i n t h e l o s s o f
im p o rta n t co n to u r in fo rm a tio n .
S uch d e g r a d a t i o n o f t h e
T h is l o s s o f in fo rm a tio n sh o u ld cause
d i f f i c u l t y i n d i f f e r e n t i a t i n g b etw e en l e t t e r s
c o n fig u ra tio n .
I t seem s t h a t t h i s i s ,
d y slex ics fre q u e n tly see l e t t e r s
of sim ila r
i n f a c t , what happens s in c e
i n c o r r e c t l y and c o n f u s e l e t t e r s
lo o k a l i k e .
Now t u r n i n g t o t h e o t h e r r e s u l t s ,
i t was f o u n d t h a t a l l
s u b j e c t s , r e g a r d l e s s o f c l a s s i f i c a t i o n , w e r e m ore s e n s i t i v e t o
seq u en cin g w ith a n g le p a r ts
th an w ith s i d e p a r t s .
A lth o u g h t h i s
th a t
r e s u l t does n o t b e a r d i r e c t l y on t h e i s s u e s a d d r e s s e d i n t h i s s t u d y ,
it
d o es s u p p o r t t h e c o n c l u s i o n o f M cF arla n d (1 9 6 5 ) and S h o n tz (1 968)
t h a t a n g l e s and s i d e s a r e i n t e g r a t e d d i f f e r e n t i a l l y w i t h i n t h e v i s u a l
sy stem .
And f i n a l l y ,
i t w as f o u n d t h a t s u b j e c t s w e r e m o re s e n s i t i v e
u n d e r t h e n o n c o n t i g u o u s c o n d i t i o n when a n g l e s w e re u s e d , w h e r e a s t h e y
w e r e m o re s e n s i t i v e u n d e r t h e c o n t i g u o u s p r e s e n t a t i o n when s i d e s w e re
used.
T h is i n t e r a c t i o n
b etw een c o n f i g u r a t i o n and c o n t i g u i t y , w h ile
r e l i a b l e , was u n e x p e c t e d a n d , t o d a t e , r e m a i n s u n e x p l a i n e d .
B ased on th e p r i n c i p l e r e s u l t s
t h a t a te m p o ra l i n t e g r a t i o n
c h ild h o o d d y s le x ia ,
d y slex ics.
d e fic it,
o f t h i s stu d y , i t
co n c lu d e d
s i m i l a r to t h a t fo u n d in
e x i s t s w i t h i n t h e v i s u a l p a th w a y o f a d u l t
I t seem s, th e r e f o r e ,
th a t th e in te g ra tio n
u n d e rly in g ch ild h o o d d y s le x ia a re n o t t r a n s i e n t ;
d e fic its
is
seem t o p e r s i s t i n t o a d u l t h o o d .
d e fic its
ra th e r th ese
Such a c o n c l u s i o n i s i n
d i r e c t c o n t r a d i c t i o n w i t h t h e b e l i e f h e l d by many t h e o r i s t s
B adcock & L o v e g ro v e , 1981; D iL o llo , H an so n , & M c I n ty r e ,
(e .g .,
1983;
Lovegrove & B row n, 1 9 7 8 ; L y l e & G o y e n , 1 9 7 5 ; O’ N e i l l & S t a n l e y , 1976)
th a t th e sensory d e f ic its
m a tu rity .
o f c h ild h o o d d y s le x ia d im in is h w ith
An i m p o r t a n t d i r e c t i o n f o r f u t u r e r e s e a r c h i s
t o c o m p are
d i r e c t l y t e m p o r a l i n t e g r a t i o n o f f o r m i n f o r m a t i o n i n a d u l t an d c h i l d
d y sle x ic s.
25
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T o l h u r s t , D. J . ( 1 9 7 3 ) . S e p a r a t e c h a n n e l s f o r t h e a n a l y s i s o f t h e
s h a p e a n d t h e movement o f a m o v i n g v i s u a l s t i m u l u s . J o u r n a l o f
P h y s io lo g y , 231, 385-402.
Van E s s e n , D. C . , & M a u n s e l l , J . H. R. ( 1 9 8 3 ) . H i e r a r c h i c a l
o r g a n i z a t i o n and f u n c t i o n a l s t r e a m s i n t h e v i s u a l c o r t e x .
Trends in N e u ro s c ie n c e s , 6 ( 9 ) , 370-375.
V e l l u t i n o , F . R. ( 1 9 7 7 ) . A l t e r n a t i v e c o n c e p t u a l i z a t i o n s o f d y s l e x i a :
Evidence in su p p o rt of v e rb a l d e f i c i t h y p o th e s is . H arvard
E d u c a t i o n a l Review, 47, 3 3 4 -3 5 4 .
29
V e l l u t i n o , F . R. ( 1 9 7 9 ) . D y s l e x i a ,
M a s s a c h u s e t t s : MIT P r e s s T
V e l l u t i n o , F. R.
4 1.
t h e o r y and r e s e a r c h . Cambridge,
(1 9 8 7 ). D y s l e x i a . S c i e n t i f i c A m erican,
256(3).
-----
34
V e l l u t i n o , F . R . , S t e g e r , B. M. , M o y e r , S . C . , H a r d i n g , C. J . , &
N i l e s , J . A. ( 1 9 7 7 ) .
Has t h e p e r c e p t u a l d e f i c i t l e d u s a s t r a y ?
J o u r n a l of L e a rn in g D i s a b i l i t i e s , J_0(6), 54-64.
V e l l u t i n o , F . R . , S t e g e r , J . A . , Ka ma n, M. , & D e S e tto , L. ( 1 9 7 5 ) .
V i s u a l form p e r c e p t i o n i n d e f i c i e n t and norm al r e a d e r s as a
f u n c t i o n o f age and o r t h o g r a p h i c r - l i n g u i s t i c f a m i l i a r i t y . C o r t e x ,
11,. 2 2 - 3 0 .
Wh y t e , J . , C u r r y , C . , H a l e , D. ( 1 9 8 5 ) . I n s p e c t i o n t i m e a n d
i n t e l l i g e n c e i n d y s l e x i c c h i l d r e n . J o u r n a l o f C h i l d P s y c h o l o g y and
P s y c h i a t r y , 2 6 ( 3 ) , 423-428.
W i l s o n , H. R. ( 1 9 7 8 ) . Q u a n t i t a t i v e c h a r a c t e r i z a t i o n o f t wo t y p e s o f
l i n e - s p r e a d fu n c tio n n ea r th e fo v e a. V is io n R esearch, 1 8(8), 971982.
—
30
APPENDIX
S e s s i o n #1
G eneral stim u lu s viewing i n s t r u c t i o n s
The b e e p y o u h e a r d i s
signifies
a warning beep.
t h a t t h e s t i m u l u s w i l l be p r e s e n t e d i n o n e s e c o n d .
th e beep s o u n d s , f i x a t e t h e s p o t s t e a d i l y .
your head.
sh ift
Do n o t b l i n k .
A fte r th e s tim u lu s has been p re s e n te d ,
your p o s i t i o n s l i g h t l y i f n e c e s s a r y .
sounds, f i x a t e the spot of l i g h t ,
If
When i t s o u n d s , i t
When
Do n o t move
y o u may b l i n k o r
Remember, when t h e b e e p
do n o t b l i n k o r move y o u r h e a d .
your eyes o r head a r e moving d u r i n g t h e s t i m u l u s
presentation,
y o u may o b s e r v e o n e o f t h e f o l l o w i n g t h i n g s .
The
f i g u r e may a p p e a r t o come a p a r t o r y o u may s e e a d o u b l e o r b l u r r e d
image.
( S u b j e c t was i n s t r u c t e d t o move h e r / h i s h e a d w h i l e t h e
s t i m u l u s was p r e s e n t e d s o t h a t s / h e c o u l d o b s e r v e t h e a f o r e m e n t i o n e d
phenomena.)
I f t h e i ma ge f r a g m e n t s , b l u r s ,
or i s
d o u b l e I w a n t you
t o a l w a y s r e s p o n d by s a y i n g " z e r o " .
B r i g h t n e s s match i n s t r u c t i o n s
The f i r s t
task.
task is
t a s k I w a n t yo u t o p e r f o r m i s a b r i g h t n e s s m a t c h i n g
I w i l l p r e s e n t t h e s t i m u l u s a number o f t i m e s i n a row .
Your
t o compare ea ch s t i m u l u s j u s t o b s e r v e d w i t h t h e j u s t
p r e v i o u s l y o b s e r v e d s t i m u l u s a n d make t h e j u d g m e n t — " B r i g h t e r " ,
"Dimmer", o r " S a m e " .
B a s e y o u r j u d g m e n t on y o u r o v e r a l l
im pression
31
o f the b rig h tn e s s of the sq u are.
Ke e p m a k i n g t h e m a t c h i n g j u d g m e n t s
as lo n g as t h e s q u a r e i s p r e s e n t e d .
R ating procedure
Now I am g o i n g t o p r e s e n t t h e s t i m u l u s f o r m i n s e v e r a l b l o c k s o f
trials,
t h e f o r m p a r t s w i l l be p r e s e n t e d s e q u e n t i a l l y h a l f t h e t i m e
and s i m u l t a n e o u s l y h a l f t h e t i m e .
The o r d e r i n w h i c h t h e s e t y p e s o f
p r e s e n t a t i o n s a r e made w i l l v a r y r a n d o m l y .
Yo ur t a s k i s
t o d e c i d e w h e th e r t h e form p a r t s were p r e s e n t e d
s i m u l t a n e o u s l y o r s e q u e n t i a l l y e a c h t i m e a n d a l s o t o g i v e me a n
e s t i m a t e o f how s u r e y o u a r e you h a v e made t h e r i g h t
th is,
you w i l l u s e a s i x p o i n t r a t i n g s c a l e .
choice.
Th e s c a l e i s
To do
as
follow s:
"I - S e q u e n t i a l ,
very sure"
"2 - S e q u e n t i a l ,
f a i r l y sure"
"3 - S e q u e n t i a l , g u e s s "
"4 - S i m u l t a n e o u s ,
guess"
"5 - S i m u l t a n e o u s ,
f a i r l y sure"
"6 - S i m u l t a n e o u s ,
very sure"
Us e " z e r o "
fo r fragm ented,
double, o r b l u r r e d images.
Now l e t ’ s p r a c t i c e u s i n g t h e s c a l e t o b e s u r e y o u h a v e t h e
l a b e l s and numbers c o r r e c t l y m a t c h e d .
( E x p e r i m e n t e r gave numbers and
s u b je c ts responded w ith th e ca te g o ry l a b e l s ,
p ractice.)
or v ice v e rsa ,
as
Now l e t ’ s p r a c t i c e w h i l e a c t u a l l y v i e w i n g t h e s t i m u l u s
presentation.
W h i l e v i e w i n g t h e s t i m u l u s yo u may s e e a d a r k a r e a
t h a t a p p e a r s t o be a b r e a k i n t h e l i n e . ' T h i s i s n o t a b r e a k i t
is
32
m e r e l y t h e g r i d l i n e s on t h e s c o p e f a c e .
It
i s i m p o r t a n t f o r you t o
i g n o r e t h i s and t o m a i n t a i n y o u r f o c u s on t h e f i x a t i o n s p o t .
P lease
g i v e t h e c o m p l e t e nu mb er a n d l a b e l c o m b i n a t i o n f o r t h e c a t e g o r y yo u
w i s h t o u s e e a c h t i m e yo u r e s p o n d .
(S u b je c t p r a c t i c e d viewing
p r e s e n t a t i o n s w i t h i n t e r p a r t i n t e r v a l s o f 20 m s e c ) .
As y o u become
more f a m i l i a r w i t h t h e t a s k work a t making your j u d g m e n t s as soon
a f t e r th e s tim u lu s p r e s e n t a t i o n as p o s s i b le .
Before each block of t r i a l s ,
I w i l l r e h e a r s e you a few t i m e s on
t h e s c a l e t o make s u r e yo u a r e u s i n g t h e n u m b e r s a n d l a b e l s
correctly.
R e me mb er , t h e p a r t s o f t h e s t i m u l u s a r e p r e s e n t e d
s e q u e n t i a l l y h a l f t h e t i m e and s i m u l t a n e o u s l y h a l f t h e t i m e .
Try to use a l l
the c a te g o rie s of the s c a le .
s h o u l d make f e w e r m i s t a k e s when y o u u s e c a t e g o r i e s
you u s e c a t e g o r i e s 2 and 5.
Likew ise,
Of c o u r s e you
I a n d 6 t h a n when
y ou s h o u l d make f e w e r m i s t a k e s
when y o u u s e c a t e g o r i e s 2 a n d 5 t h a n when you u s e c a t e g o r i e s 3 a n d 4.
( S u b j e c t s were g iv e n p r a c t i c e i n v iew in g t h e s t i m u l u s
p resentations).
Now we w i l l b e g i n t h e f i r s t
o f two t r a i n i n g s e s s i o n s .
The
p u r p o s e o f t h e s e t r a i n i n g s e s s i o n s i s t o a l l o w yo u t o d e v e l o p
c r i t e r i a f o r y o u r j u d g m e n t s o f how t h e f o r m p a r t s w e r e p r e s e n t e d ,
that is ,
that
s e q u e n tia lly or sim ultaneously.
I t is extrem ely im portant
you m a i n t a i n a c o n s i s t e n t l e v e l o f a t t e n t i o n a t a l l
you a r e v i e w i n g t h e d i s p l a y .
t i m e s when
You s h o u l d d e t e r m i n e t h e l e v e l o f
a t t e n t i o n yo u c a n m a i n t a i n d u r i n g t h i s
train in g session.
Then
m a i n t a i n t h a t s ame l e v e l o f a t t e n t i o n o n c e t h e d a t a c o l l e c t i o n
sessions
begin.
I f anything i s
k e e p i n g you f r o m g i v i n g t h e d i s p l a y
33
your undivided a t t e n t i o n ,
l e t me know a n d we w i l l s t o p a n d a t t e m p t t o
c o rrec t the s itu a tio n .
You s h o u l d be w o r k i n g t o w a r d e s t a b l i s h i n g a d e f i n i t e s e t o f
c r i t e r i a f o r your judgm ents of th e d i s p l a y d u rin g t h i s s e s s i o n .
By
t h e e n d o f t o d a y ' s s e s s i o n yo u s h o u l d h a v e i n m i n d t h e
c h a r a c t e r i s t i c s o f t h e d i s p l a y w h i c h d i f f e r e n t i a t e f o r yo u between
t h e s e q u e n t i a l and s i m u l t a n e o u s p r e s e n t a t i o n o f form p a r t s .
( T h e r a t i n g s c a l e was r e v i e w e d a t t h i s p o i n t . )
(G eneral view in g i n s t r u c t i o n s were r e v i e w e d . )
P resen tatio n conditions
Rem em be r, t h e f o r m p a r t s a r e p r e s e n t e d s e q u e n t i a l l y h a l f t h e
tim e and s i m u l t a n e o u s l y h a l f t h e t i m e .
c o n d itio n s a re p r e s e n te d i s random.
The o r d e r i n w h ic h t h e s e
T h e r e f o r e , t h e r e i s no p a t t e r n
t o t h e o r d e r i n which th e c o n d i t i o n s a r e p r e s e n t e d .
c o n d i t i o n can o cc u r s e v e r a l
p a t t e r n s can occu r.
T h e same
t i m e s i n a row o r any c o m b i n a t i o n o f
Base y o u r j u d g m e n t s o l e l y on t h e c h a r a c t e r i s t i c s
you o b s e r v e i n t h e s t i m u l u s p r e s e n t a t i o n .
Do n o t b a s e y o u r r e s p o n s e
on a p a r t i c u l a r p a t t e r n o f p r e v i o u s r e s p o n s e s .
Try to use a l l
t h e c a t e g o r i e s o f t h e s c a l e when r e s p o n d i n g .
H o w e v e r , do n o t f o r c e a d i s t r i b u t i o n o f y o u r r e s p o n s e s among t h e
categ o ries
i n any a r t i f i c i a l
manner.
In o th e r words,
call
t hem t h e
way y o u s e e t h e m b a s e d o n y o u r c r i t e r i a .
R e me mb er , when u s i n g t h e s c a l e c a t e g o r i e s , y o u s h o u l d make f e w e r
m i s t a k e s when yo u u s e c a t e g o r i e s
I a n d 6 ( v e r y s u r e ) t h a n when you
use c a t e g o r i e s 2 and 5 ( f a i r l y s u r e ) .
L i k e w i s e , y o u s h o u l d make
34
f e w e r m i s t a k e s w i t h c a t e g o r i e s 2 a n d 5 t h a n you do w i t h c a t e g o r i e s
3
and 4 - t h e g u e s s c a t e g o r i e s .
S e s s i o n #2
G eneral i n s t r u c t i o n s
This i s the second of the t r a i n i n g s e s s i o n s .
By now y o u s h o u l d
have your c r i t e r i a f o r t h e s e q u e n t i a l and s i m u lt a n e o u s ju dgm ents
f a i r l y w e l l i n m i n d . . T od ay you s h o u l d be f u r t h e r
confirm ing th ese
c r i t e r i a and w o rk in g t o w a r d s f i n e r d i s c r i m i n a t i o n s i n u s i n g t h e
v a r i o u s c a t e g o r i e s o f s e q u e n t i a l and s i m u l t a n e o u s .
Remember , k e e p y o u r a t t e n t i o n l e v e l
consistent.
tow ards c o n s is te n c y i n th e use o f your c r i t e r i a .
A l s o work
C onsistency in
t h e s e t wo a r e a s i s e x t r e m e l y i m p o r t a n t d u r i n g t h e d a t a c o l l e c t i o n
sessions.
(S u b jects p r a c tic e d use of the r a t i n g s c a le .)
(G eneral viewing i n s t r u c t i o n s were re v ie w e d .)
( P r e s e n t a t i o n c o n d i t i o n s were r e v ie w e d . )
S e s s i o n s 3,
4 , a nd 5
G eneral i n s t r u c t i o n s
This i s
the
(first,
second,
th ird )
data c o lle c tio n sessio n .
Remember , a c o n s i s t e n t l e v e l o f a t t e n t i o n i n v i e w i n g t h e s t i m u l u s and
c o n s is te n t use of the ca te g o ry r a t i n g s c a le are a b s o lu te ly e s s e n t i a l .
( S u b j e c t s were g i v e n p r a c t i c e i n u s e o f t h e r a t i n g s c a l e . )
(G e n era l v iew in g i n s t r u c t i o n s were r e v ie w e d . )
( P r e s e n t a t i o n c o n d i t i o n s were re v ie w e d .)
■
35
G i v e me t h e c o m p l e t e n u m b e r - l a b e l c o m b i n a t i o n o f t h e r a t i n g
s c a l e d u r i n g t h e warm-up t r i a l s .
trials
At t h e b e g i n n i n g o f e a c h b l o c k o f
g i v e me t h e c o m p l e t e n u m b e r - l a b e l c o m b i n a t i o n f o r t h e f i r s t
few t r i a l s .
Then f o r t h e r e s t o f t h e t r i a l s
in the block,
you may
d r o p t h e l a b e l a n d g i v e o n l y t h e c a t e g o r y num be r a s a r e s p o n s e .