dyslexia: a different perceptual strategy, and how to learn a new strategy for reading. gadi geiger...
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Dyslexia: a different perceptual strategy, and how to learn a new strategy for reading.
Gadi Geiger
Center for Biological and Computational LearningBrain and Cognitive Sciences
McGovern Institute for Brain ResearchMassachusetts Institute of Technology
Cambridge MA 02139
gadi@ai.mit.edu
Developmental dyslexia: some references Orton: Modern dyslexiaGillingham, A and Stillman, B, (1970), ‘Remedial training for .. General developmental (lag) issues:Frostig, M. and Horne, D. (1964) The Frostig Program ..ButLewis, J.N. (1968), J. of Learning Disabilities 1 (11): 652-653. Brain anatomy, ectopias and auto-immune/hormonal issues:Galaburda, A.M et Al. (1985), Ann. Neurol 18: 222-233. Language deficit and phoneme awareness:Liberman, I.Y. (1971), Bull. Orton Soc. 21: 71-87.Velutino, F. R. (1987) ‘Dyslexia’ Sci. Am., 256(3), 34-42. Auditory deficits:Tallal, P. and Katz, W. (1989) in Brain and Reading Wright, B.A. et al. (1997), Nature 387: 176-178.
Visual evidence:Misalignment of the two eyes:Stein, J.F. and Fowler, M.S. (1981), TINS 4: 77-80. Transient and sustain sub-systems hypothesis:Lovegrove, W.J. et al.(1986), Cog. Neuropsychol 3: 225-267. The magnocellular pathway deficit hypothesis:Livingstone, et al. (1991), Proc. Natl. Acad. Sci. USA 88: 7943-. Visual stability and the generalized magnocellular hypothesis:Stein, J. and Walsh, V. (1997), TINS 20: 147-152.But:E.g: Amitay, S. et al. (2002), Brain, 125(10): 2272-2285. Tactile evidence:Grant, A.C. et al. (1999), Neuropsychologia 37, 1202-1211 Attention:Facoetti, A. et al. (2003). Cog. Brain Res. 16, 185-191.
Epidemiology and some numbers:Rutter,M and Yule. W., (1975). Psychiatry, 16 181-197.Shaywitz, S.E. et al..(1992), (distribution) N. Engl. J. Med. 326, 145-150.Shaywitz, S.E. et al. (1990) (boys girls) JAMA 264, 998-1002. “National” frequency of dyslexia:Lindgren, S.D. et al. (1985),’ Child Development 56, 1404-1417. Definitions of dyslexia:The World Federation of Neurology: “A disorder manifested by difficulty in learning to read despite conventional instruction, adequate intelligence and sociocultural opportunity….”Critchley, M. (1970), ‘The dyslexic child’ Springfield Ill. or language based:Shaywitz B. A.et al.(1992). J. Child Neurol.
Collaborators:
-Jerry Lettvin, MIT
-Olga Zegarra-Moran in SISSA, Trieste Italy, (at the time).
-Manfred Fahle, in Tübingen, Germany, (at the time).
In:IRCCS “E. Medea”, La Nostra Famiglia,
Bosisio Parini, ItalySilvia PesentiMaria Luisa LorussoCarmen CattaneoRaffaella GalliAndrea Facoetti Massimo MolteniUberto Pozzoli
x
N T
x
M S
x
H V
151050-5-10-150
20
40
60
80
100
The form-resolving field (FRF) of English-native adults
angular distance from center of gaze [degrees]
corr
ect
reco
gniti
on
[%]
ordinary readers (OR)
151050-5-10-150
20
40
60
80
100
The form-resolving field (FRF) of English-native adults
angular distance from center of gaze [degrees]
corr
ect
reco
gniti
on
[%]
ordinary readers (OR)
dyslexics
dyslexics
OR
151050-5-10-150
20
40
60
80
100
The form-resolving field (FRF) of English-native adults
angular distance from center of gaze [degrees]
corr
ect
reco
gniti
on
[%]
ordinary readers (OR)
dyslexics
the differences in recognition
151050-5-10-150
20
40
60
80
100
The form-resolving field (FRF) of English-native adults
angular distance from center of gaze [degrees]
corr
ect
reco
gniti
on
[%]
ordinary readers (OR)
dyslexicsthe extent of recognition
difference
151050-5-10-150
20
40
60
80
100
Numerical characterization of the FRF:criterion C2
angular distance from center of gaze [degrees]
corr
ect
reco
gniti
on
[%]
+
deg 12.5at correct % deg 10at correct %
deg 2.5at correct %C2
Telling dyslexics and ordinary readers apart: the diagnostic power of C2.
C2dyslexic is person the then 2
reader ordinary an is person the then 2
The C2 criterion tells 87% of the tested person correct.
The average FRFs of dyslexics, ordinary readers and poor readers
0
20
40
60
80
100
-15 -10 -5 0 5 10 15
eccentricity [degree]
corr
ect
reco
gn
itio
n [
%]
ordinary readers
dyslexics
151050-5-10-150
20
40
60
80
100
corr
ect
reco
gniti
on [
%]
The FRF’s of the three Boder type dyslexics
angular distance from center of gaze [degrees]
151050-5-10-150
20
40
60
80
100
Cor
rect
rec
ogni
tion
%The FRF’s of the three Bakker type dyslexics
angular distance from center of gaze [degrees]
The way we see is not determined by what we want to see but how we have learned to practice seeing. There are several strategies that we pick between depending on what we have learned to see, and we switch between them as the task changes. So for example, a hunter uses a wide field of vision to locate prey,a scribe uses a narrow field to write and a painter or architectuses a variable field to arrange an ensemble into a whole. Eachdiscipline of seeing take practice. But suppose, like a dyslexic,you have a strategy inappropriate to reading.
When ordinary readers look at text
The way we see is not determined by what we want to see but how we have learned to practice seeing. There are several strategies that we pick between depending on what we have learned to see, and we switch between them as the task changes. So for example, a hunter uses a wide field of vision to locate prey,a scribe uses a narrow field to write and a painter or architectuses a variable field to arrange an ensemble into a whole. Eachdiscipline of seeing take practice. But suppose, like a dyslexic,you have a strategy inappropriate to reading.
When dyslexics look at text
151050-5-10-150
20
40
60
80
100
The form-resolving field (FRF) of English-native adults
angular distance from center of gaze [degrees]
corr
ect
reco
gniti
on
[%]
ordinary readers (OR)
dyslexics
dyslexics
OR
151050-5-10-150
20
40
60
80
100
The form-resolving field (FRF) of Hebrew-native adults
angular distance from center of gaze [degrees]
corr
ect
reco
gniti
on
[%]
ordinary readers (OR)
dyslexics
dyslexics
OR
151050-5-10-150
20
40
60
80
100
The form-resolving field (FRF) of a “conditional dyslexic”
angular distance from center of gaze [degrees]
corr
ect
reco
gniti
on
[%]
In the “alert” phase
151050-5-10-150
20
40
60
80
100
in the “tired” phase
tired
alert
The form-resolving field (FRF) of a “conditional dyslexic”
angular distance from center of gaze [degrees]
corr
ect
reco
gniti
on
[%]
In the “alert” phase
Demonstrating lateral masking
N x TENET
Keep your gaze on the x without moving your eyes
X
10864200
20
40
60
80
Co
rre
ct
rec
og
nit
ion
%
Eccentricity deg.
D FMT
10864200
20
40
60
80
Co
rre
ct
rec
og
nit
ion
%
Eccentricity deg.
FMTM
Demasking
Central speaker
Fixation point
The auditory experimental set-up
Auditory perception of words
0
20
40
60
80
100
stimuli only in the presenceof speech mask
in the presenceof noise mask
correc
t reco
gnition %
from the central stimuli
0
10
20
30
stimuli andspeech mask
periphery to cen
tral ratio
dys.
OR
and from the mask
Peripheral to central ratio of letter recognition
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
C1/2 C1/2R
rati
o Dys
OR
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 10 20 30 40 50 60 70 80
Auditory: ra tio of peripehera l to centra l w ord recognition
Vis
ua
l: p
eri
ph
era
l to
ce
ntr
al r
ati
o (
C1
/2R
)
dys lex ics
OR
Corre la ting individua l a uditory w ith visua l m e a sure s
From Gilbert et al. 2001
The regimen of practice for learning a new perceptual strategy
The practice comprises two parts:
• Novel, small-scale, hand-eye coordination tasks likepainting, drawing, modeling, embroidery etc..
• Reading with a window-mask.
The way we see is not determined by what we want to see but how we have learned to practice seeing. There are several strategies that we pick between depending on what we have learned to see, and we switch between them as the task changes. So for example, a hunter uses a wide field of vision to locate prey,a scribe uses a narrow field to write and a painter or architectuses a variable field to arrange an ensemble into a whole. Eachdiscipline of seeing take practice. But suppose, like a dyslexic,you have a strategy inappropriate to reading.
The way we see is not determined by what we want to see but how we have learned to practice seeing. There are several strategies that we pick between depending on what we have learned to see, and we switch between them as the task changes. So for example, a hunter uses a wide field of vision to locate prey,a scribe uses a narrow field to write and a painter or architectuses a variable field to arrange an ensemble into a whole. Eachdiscipline of seeing take practice. But suppose, like a dyslexic,you have a strategy inappropriate to reading.
The way we see is not determined by what we want to see but how we have learned to practice seeing. There are several strategies that we pick between depending on what we have learned to see, and we switch between them as the task changes. So for example, a hunter uses a wide field of vision to locate prey,a scribe uses a narrow field to write and a painter or architectuses a variable field to arrange an ensemble into a whole. Eachdiscipline of seeing take practice. But suppose, like a dyslexic,you have a strategy inappropriate to reading.
The way we see is not determined by what we want to see but how we have learned to practice seeing. There are several strategies that we pick between depending on what we have learned to see, and we switch between them as the task changes. So for example, a hunter uses a wide field of vision to locate prey,a scribe uses a narrow field to write and a painter or architectuses a variable field to arrange an ensemble into a whole. Eachdiscipline of seeing take practice. But suppose, like a dyslexic,you have a strategy inappropriate to reading.
Reading with a window-mask
The way we see is not determined by what we want to see but how we have learned to practice seeing. There are several strategies that we pick between depending on what we have learned to see, and we switch between them as the task changes. So for example, a hunter uses a wide field of vision to locate prey,a scribe uses a narrow field to write and a painter or architectuses a variable field to arrange an ensemble into a whole. Eachdiscipline of seeing take practice. But suppose, like a dyslexic,you have a strategy inappropriate to reading.
The way we see is not determined by what we want to see but how we have learned to practice seeing. There are several strategies that we pick between depending on what we have learned to see, and we switch between them as the task changes. So for example, a hunter uses a wide field of vision to locate prey,a scribe uses a narrow field to write and a painter or architectuses a variable field to arrange an ensemble into a whole. Eachdiscipline of seeing take practice. But suppose, like a dyslexic,you have a strategy inappropriate to reading.
Reading with a window-mask
The way we see is not determined by what we want to see but how we have learned to practice seeing. There are several strategies that we pick between depending on what we have learned to see, and we switch between them as the task changes. So for example, a hunter uses a wide field of vision to locate prey,a scribe uses a narrow field to write and a painter or architectuses a variable field to arrange an ensemble into a whole. Eachdiscipline of seeing take practice. But suppose, like a dyslexic,you have a strategy inappropriate to reading.
The way we see is not determined by what we want to see but how we have learned to practice seeing. There are several strategies that we pick between depending on what we have learned to see, and we switch between them as the task changes. So for example, a hunter uses a wide field of vision to locate prey,a scribe uses a narrow field to write and a painter or architectuses a variable field to arrange an ensemble into a whole. Eachdiscipline of seeing take practice. But suppose, like a dyslexic,you have a strategy inappropriate to reading.
Reading with a window-mask
Tübingen Brookline0.0
1.0
2.0
experimental-dyslexics
reference-dyslexics
Gra
des
Improvements in reading after 3 months of practice
151050-5-10-150
20
40
60
80
100
Cor
rect
rec
ogni
tion
%
The FRF of the experimental dyslexics
before
afterOR
before and after 3 months of practice
angular distance from center of gaze [degrees]
0-2-4-6-8-10
word ident.
comprehension
word attack
before
after
before and after practice
grades
Reading levels of 14 adult dyslexics
86420
.
.
.
.
.
.
.
.
.
grades
improvements
("0" is the expected level for each individual)
*
*
*
( * - denotes significance better than 0.05)
151050-5-10-150
20
40
60
80
100
The form-resolving field (FRF) of English-nativeDyslexics
before and after practice
angular distance from center of gaze [degrees]
corr
ect
reco
gniti
on
[%]
before
after
OR
0-1-2-3-4
G-L practice
Logopedia
before
after
Accuracy of reading
SD
210
.
.
.
.
.
.
SD
improvements
*
(reading levels are indicated by standard deviation (SD) units from the expected norm)
0-1-2-3
G-L practice
Logopedia
before
after
Speed of reading
SD
210
.
.
.
.
.
.
SD
improvements
*
Reading of passages and word-lists by dyslexic children
0-1-2-3
G-L practice
Logopedia
before
after
Accuracy of reading non-words
SD210
.
.
.
.
.
.
SD
improvements
*
0-1-2-3-4
G-L practice
Logopedia
before
after
Speed of reading non-words
SD
210
.
.
.
.
.
.
SD
improvements
*
Reading non-words
improvements
improvements
86420
G-L practice
Logopedia
before
after
Fusing syllables to words
errors
420
.
.
.
.
.
.
improvements
*
Measuring auditory-phonemic skills
6420
G-L practice
Logopedia
before
after
Omitting syllables from words
errors
420
.
.
.
.
.
.
improvements
*
151050-5-10-150
20
40
60
80
100
Smooth and jagged letters
angular distance from center of gaze [degrees]
corr
ect
reco
gniti
on
[%]
The FRF of adult ordinary readers when presented with
smooth lettersjagged letters
jagged
-Dyslexics and ordinary readers differ in their visual and auditory perceptual strategies. A wide strategy for dyslexics and a narrow one for ordinary readers.
-The strategies differ mainly in their neural tuning and coding specificity, that leads to different distributions of lateral masking and the pattern of attention. -The wide perceptual strategy explains why reading ordinarily is difficult or almost impossible for dyslexics. -Dyslexics are able to learn a narrow strategy for reading by practice.
-This practice results in cross sensory-modality learning.
Main points
-3
-2
-1
0
1initial
final
Gra
de
s
The initial and final reading scoresof 24 dyslexic children
151050-5-10-150
20
40
60
80
100
The form-resolving field adults
angular distance from center of gaze [degrees]
corr
ect
reco
gniti
on
[%]
Ordinary readers“speed readers”
OR
speed readers
Line drawings of objects used as stimuli
151050-5-10-1520
40
60
80
100
The form-resolving field (FRF)of adult ordinary readers
angular distance from center of gaze [degrees]
corr
ect
reco
gniti
on
[%]
large letters “objects”
letters
objects
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