To appear in Cortex
Developmental surface dyslexias
INTRODUCTION
DEVELOPMENTAL SURFACE DYSLEXIAS
The definition of surface dyslexia relates to the way individuals with this dyslexia read:
Naama Friedmann and Limor Lukov
they read via grapheme-to-phoneme conversion. But why do they read via this route?
(Tel Aviv University)
Which part of the lexical route is impaired? This definition does not specify which
component of the reading process is impaired. A look at the model for reading suggests that
ABSTRACT
Individuals with surface dyslexia read via grapheme-to-phoneme conversion due to a
deficit in the lexical route. A deficit in the lexical route can be caused by impairments at
several different loci. In the current study we identify 3 subtypes of developmental surface
dyslexia, each caused by impairment at a different locus on the lexical route. Each subtype
shows a different pattern of performance in various tasks. All three subtypes show the
classical pattern of reading aloud, with regularization and difficulty in reading words that
have more than a single possible conversion to a phoneme string, but they differ in their
performance in lexical decision and homophone comprehension. The first subtype, input
surface dyslexia, results from a deficit to the orthographic input lexicon, and entails poor
performance in lexical decision and comprehension tasks. The second subtype,
orthographic lexicon output surface dyslexia, in which the orthographic input lexicon is
accessible but its output to the phonological output lexicon and to the semantic system is
impaired, allows normal lexical decision, but causes impaired comprehension of
homophones. The third subtype, interlexical surface dyslexia, caused by a selective deficit
in the connection between the orthographic input lexicon and the phonological output
lexicon but with intact access from the orthographic input lexicon to the semantic system,
allows normal performance in lexical decision and comprehension tasks. Seventeen
Hebrew-speaking individuals with developmental surface dyslexia aged 10-43 participated
in the study, 8 of them showed the first pattern, 3 showed the second pattern, and 6
displayed the third pattern. Another result of the study pertains to the importance of the
lexical results of grapheme-to-phoneme conversion for each target word. Some words,
when read via grapheme-to-phoneme conversion, can potentially be read as other words
(such as "now" in English, which can be sounded as the word "know"), we term these
words potentiophones. The results indicate that potentiophones yield the highest error rate
in reading aloud for all the participants with surface dyslexia.
several different impairments to various parts of the lexical route can cause surface
dyslexia. In the current study we focus on developmental surface dyslexia and show that at
least three different loci on the lexical route can be impaired, causing three different
subtypes of developmental surface dyslexia, which differ in the patterns of performance in
various tasks.
orthographic -visual analysis:
letter identification
letter position letter-word binding
orthographic
input lexicon
semantics
phonological
output lexicon
grapheme-to-phoneme
conversion
phonemic buffer
Figure 1. A model of single word reading. The numbers indicate possible loci of impairment that
lead to developmental surface dyslexia.
When the lexical route is unavailable, readers may be forced to rely on the grapheme-tophoneme route for oral reading. Looking more closely into what can cause the lexical route
to be unavailable, several possible loci of impairment emerge: one might be the
orthographic input lexicon or the access to it (
This article is dedicated to the memory of John Marshall, who led the way in the classification of dyslexias,
was the first to describe surface dyslexia in detail, and deeply believed that developmental dyslexias can and
should be classified similarly to acquired dyslexias. Shalom, John. We thank Dror Dotan, Ivana NachmanKatz, Julia Reznick, Maya Yachini, Michal Biran, Terri Sternberg, and Uri Hadar for their helpful comments
on the paper. This research was supported by the Israel Science Foundation (grant no. 1296/06, Friedmann).
Address correspondence Naama Friedmann, e-mail: [email protected]
in Figure 1). Another possibility is that the
orthographic input lexicon itself is intact and accessible, but its output is damaged: either its
output both to the phonological output lexicon and to the semantic system (marked
Figure 1), or only the output to the phonological lexicon (marked
intact access to the semantic system.
in
in Figure 1), with
2
Developmental surface dyslexias
3
Developmental surface dyslexias
Grapheme-to-phoneme reading can also result from an impairment to the semantic
Finally, individuals with an impairment of the third subtype – whose impairment results
system, to the phonological output lexicon, or its access to the phonemic output buffer
from a disconnection between the orthographic input lexicon and the phonological output
(Jackson and Coltheart, 2001) but in these cases surface dyslexia is part of a more general
lexicon – are expected to perform well both in lexical decision tasks and in comprehension
language or semantic impairment, and is not restricted to reading, and we will not explore
tasks, when these tasks do not involve oral reading. This is because they have intact access
these subtypes in the current study.
to the orthographic input lexicon and from it to the semantic system. Only when they read
These three impairments are expected to yield a similar pattern of reading aloud. Since
all three impairment loci cause reading via conversion rules, all three impairments result in
aloud will their surface dyslexia be manifested, because they will be forced to use the
grapheme-to-phoneme route2.
regularizations in reading aloud. However, importantly, the three impairments should differ
Thus, in order to determine the locus of impairment for each individual with surface
with respect to their expected effect on lexical decision and comprehension. The first
dyslexia, reading aloud is not enough. Their performance in lexical decision, and
impairment - involving lack of access to the orthographic input lexicon, or impaired
specifically their ability to reject pseudohomophones (nonwords that can be sounded out
orthographic input lexicon1 - would result both in difficulty in lexical decision and in
like real words, such as fone), would indicate whether the orthographic input lexicon is
impaired comprehension. Namely, this deficit will result in inability to determine whether a
accessible, and comprehension tasks of homophones might speak for whether or not there is
letter string forms an existing word, especially when it can be sounded out via grapheme-
access to the semantic system from the orthographic input lexicon (Marshall, 1984a).
to-phoneme conversion as an existing word. The comprehension in this type of impairment
In a seminal study of acquired surface dyslexia, Coltheart and Funnell (1987) identified
will rely solely on the phonological output of the grapheme-to-phoneme conversion. Thus,
seven loci that might lead to acquired surface dyslexia. They were able to show that their
words that are regular and non-homophonous might be understood correctly, but irregular
patient, HG, had surface dyslexia that resulted from a deficit in the orthographic input
words and homophones would either not be recognized as a word and thus not be
lexicon (in entries within it or in the access to it). Other individuals with a similar
understood, or be recognized as a different word and misunderstood. For example, if a
impairment to the orthographic input lexicon are NW, reported by Weekes and Coltheart
word like “yacht” would be read as yakt, the reader might say that she does not recognize
(1996), and EE, reported by Howard and Franklin (1987) and Coltheart and Byng (1989;
the word. A word like “sale”, when identified solely on the basis of the phonological
although EE also had considerable output impairments). Their locus of impairment was
lexicon, might be defined as “To move along the sea with a boat”, and a word like “too”
identified on the basis of poor reading of irregular words, poor lexical discrimination (in
might be defined as “The number after one”.
which participants were asked to select the word in word/pseudohomophone pairs), and
Individuals with an impairment of the second subtype - impaired connection from the
poor homophone comprehension. A recent report of MM, a Spanish-speaking individual
orthographic input lexicon to both the phonological output lexicon and the semantic system
with surface dyslexia, also described a deficit to the input lexicon (Ferreres et al., 2005).
- would be able to decide whether a letter sequence is a word or not, even when it is a
The patients described by Marshall and Newcombe, JC and MS (Marshall and Newcombe,
pseudohomophone, as they have access to the orthographic input lexicon. Because they do
1973; Newcombe and Marshall, 1981, 1984, 1985) also fit the description of an impaired
not have access to semantics, they will fail in comprehension in much the same way as the
orthographic input lexicon (JC is taken to be such a case, although data are available only
first subtype.
2
1
Ascribing a deficit to the orthographic input lexicon still leaves the question open whether the deficit is in
processes operating in and on the lexicon, or whether the representations in the lexicon are impaired (for
example, "faded", and require additional activation to be accessed).
Theoretically, when the pathway between the lexicons is impaired, one can also use the route from
semantics to the phonological output lexicon in order to read aloud. However, whereas this route is the natural
route for word retrieval, it does not seem to be a natural route for reading, and this is why the arrow appears
dashed in Figure 1. It seems to be a last resort, used only when no other route is available for reading, as is the
case in deep dyslexia. We will return to this point in the discussion, on the basis of our results.
4
Developmental surface dyslexias
with respect to his impaired reading of irregular words and his impaired comprehension of
homophones; see Ellis et al., 2000).
5
Developmental surface dyslexias
As far as we know, whereas cases of developmental surface dyslexia were reported in
the literature (Broom and Doctor 1995a; Castles et al., 2006; Castles and Coltheart, 1993,
Another subtype of acquired surface dyslexia that has been reported in the literature is
1996; Coltheart, 1987; Coltheart et al., 1983; Judica et al., 2002; Masterson, 2000; Temple,
central or semantic surface dyslexia, which was described as resulting from a deficit to the
1997), and whereas, on the basis of the reading model, subtypes are expected in
semantic system. Such cases are HTR (Shallice et al., 1983), MP (Bub et al., 1985), KT
developmental surface dyslexia as well (Castles, 2006), until now no study identified
(McCarthy and Warrington, 1986; Patterson and Hodges, 1992), and JL and GC (Graham et
subtypes in the developmental form of surface dyslexia. In the current study we examine
al., 1994). Notice, however, that if only the semantic system was impaired in these cases, it
whether such subtypes also exist in developmental surface dyslexia. We test reading in
is not clear why the patients did not use the direct lexical route to read irregular words, but
Hebrew, which, due to its extremely irregular orthography, is a very good testing ground
rather the sublexical route. A lesion that is restricted to the semantic system does not suffice
for surface dyslexia, and a very easy language to identify such a dyslexia.
to account for reading via the sublexical route, especially given reports in the literature of
individuals with severely compromised comprehension whose reading of irregular words
A bit about Hebrew
was unimpaired (cf., Blazely et al., 2005; Cipolotti and Warrington, 1995; Schwartz et al.,
When is reading via grapheme-to-phoneme conversion especially problematic? When
1979, 1980), and an additional impairment might be responsible for the inability to read via
many written words cannot be converted to a unique phoneme string. Hebrew is exactly
the direct lexical route.
such a language, in which no word can be converted unambiguously to phonemes.
One other subtype of acquired surface dyslexia reported is sometimes termed "output
Hebrew is a Semitic language, read from right to left. It has 22 letters, 9 of them with
surface dyslexia". These are typically cases of individuals with impaired naming and
ambiguous conversion to phonemes – 4 that can be mapped onto two different consonantal
impaired phonological output lexicon, who succeed in written word comprehension and
sounds, and 5 letters that can serve either as a vowel (or several vowels) or as a consonant
lexical decision. Such patients are EST (Kay and Ellis, 1987; Kay and Patterson, 1985),
(see Appendix A). This is the first source of ambiguity in reading via grapheme-to-
MK (Howard and Franklin, 1987), and FM (Graham et al., 1994). Their deficits are in the
phoneme conversion in Hebrew. Another source is the underrepresentation of vowels. The
phonological output lexicon or in its output to the phonemic buffer.
vowels /a/ and /J/ are almost never represented in writing (except for at the end of words,
Notice, however, that the latter two subtypes, semantic and output surface dyslexia, are
where they are both represented by the same letter), with the result that words that sound
in fact not selective types of surface dyslexia but are rather cases of impairment to
completely different are written exactly the same way. For example, /sefer/ (book), /safar/
components that are not specific to reading, the semantic system or the phonological output
(counted), and /sfar/ (frontier) are all written SFR,
lexicon. Only the first subtype, in which orthographic input lexicon is impaired, is specific
are both written MTR,
; and KRX,
; /meter/ (meter) and /matar/ (rain)
, stands for both /kerax/ (ice) and /kere’ax/
in Figure 1) are different
(bald). The vowels /i/, /o/ and /u/ are represented only in some of the words. Even when a
– they relate to impairments in the connection from the orthographic input lexicon to the
vowel is represented orthographically by a letter, this letter is usually ambiguous between
semantic system and the phonological output lexicon, which are still part of the reading
several vowels and consonants (the letter " ", for example, can be read as /o/, /u/, or /v/).
process, rather than to damage to the phonological and semantic components themselves,
Thus, a word can comprise only consonant letters (even 7 and 8-letter words like
to reading. The two other options we described (marked
and
which are already used for other language modalities. The disconnections we described can
HTPRSMTM, /hitparsamtem/, and MTGLGLT /mitgalgelet/), and the vowels and the stress
appear without a deficit to comprehension of auditorily presented words and without
should be added in reading based on orthographic-lexical knowledge of the word, or some
naming deficits.
frequency preference. Furthermore, stress is not represented in the orthography, and stress
6
Developmental surface dyslexias
position in Hebrew is lexically specified (Bat-El, 1993), so the word XRS,
7
Developmental surface dyslexias
can be read
more sensitive to surface dyslexia reading than other irregular words, because the reading
both with an initial stress, /xeresh/ (silently), and with final stress, /xeresh/ (deaf) (as well
of irregular words that do not have potentiophones results in a non-lexical response.
as /xarash/, plowed). This means that irregularity takes a wider sense in the case of
Because some individuals with surface dyslexia have a strong tendency to produce real
Hebrew: it is not only the case that a letter or a group of letters can be converted into more
words as output (Patterson et al., 1985, p. 12), this non-lexical response may be identified
than a single sound, but also that the lack of letters (mainly vowel letters) creates ambiguity
by the reader as incorrect, and corrected immediately in an attempt to reach a lexical
with respect to conversion to sound.
response. An incorrect reading of a potentiophone, however, yields an existing word, and
The result of these properties of Hebrew orthography is that in fact no word can be read
hence does not allow the detection of the error.
unambiguously via grapheme-to-phoneme conversion, although some conversions might be
In the current study we used these characteristics of Hebrew orthography to examine
favorable. Even 3-letter words might theoretically have several thousands of possible
surface dyslexia, and more specifically three subtypes of developmental surface dyslexia.
readings. For example, in the word
, QBS, each of the three letters can be converted to
either of two consonants, and the vowels are not represented, so after each letter one of six
We also explored the way surface dyslexia is manifested in a highly irregular language like
Hebrew.
vowels can be used. Together with the two possible stress positions, this leads to
2*2*2*6*6*6*2 = 3456 theoretical ways to read the word, which the orthographic lexicon
narrows down to three lexical options.
Another result of this structure of Hebrew orthography that is important for the
description of surface dyslexia is the abundance of potentiophones (Gvion and Friedmann,
EXPERIMENTAL INVESTIGATION
Participants
The participants with surface dyslexia were individuals who had developmental
2001; Lukov and Friedmann, 2006). We use the term potentiophones for word pairs that are
dyslexia, who were diagnosed with “learning disabilities” or “reading disabilities” prior to
written differently and sound differently, but whose letter sequence can be mapped onto the
the study. We included them in the study based on the number and types of errors they
same sound string. Therefore when such a word is read solely via grapheme-to-phoneme
made in single word reading. Participants were included in the study only if their reading
conversion, it can be read aloud as the other existing word, which sounds differently. An
aloud (see Method section) included significantly more errors than the control group, and
example in English is the word now that can be read as no or know when read via
the type of errors they made in reading were errors that result from reading via grapheme-
grapheme-to-phoneme conversion (other examples for English potentiophones are resent-
to-phoneme conversion: regularizations, errors in vowel pattern of unvoweled words or
recent, come-comb, bear-beer, angle-angel, talk-talc, and whose-hose). Examples for
words with ambiguous vowel letters, and potentiophone errors. The comparison of each
potentiophones in Hebrew are the pairs
crown),
-
-
(KtR-QTR, /katar/-/keter/, locomotive-
(QMO-KMO, /kmo/-/kamu/, like-woke up), and
-
(XOL-XBL,
/xol/-/xevel/, sand-rope).
participant to her/his control group was done using the Crawford and Howell’s (1998) t-test
for the comparison of a single participant to a group.
This created a group of 17 participants, 6 female and 11 male. Their background
Potentiophones are valuable for the diagnosis of surface dyslexia, because reading aloud
information is presented in Table 1. All the participants with developmental surface
of these words can already indicate whether or not the reader used her lexical route for
dyslexia had normal IQ, and studied in regular schools and regular classes. They had
reading. They are better for the detection of surface dyslexia than homophones, because
normal language, their spontaneous speech was normal and none of them was diagnosed
homophones sound the same and thus reading aloud cannot indicate whether they were read
with SLI (Specific Language Impairment). Four of the participants (TM, OM, BZ, YD)
correctly or not, and therefore require comprehension tasks. Potentiophones might also be
were also tested with spoken language test batteries for the diagnosis of syntactic
8
Developmental surface dyslexias
9
Developmental surface dyslexias
impairments (BAMBI, Friedmann and Novogrodsky, 2002; BAFLA, Friedmann, 1998),
to three groups of individuals without reading or language impairments to attain reference
and a test battery for the assessment of phonological abilities (BLIP, Friedmann, 2003),
scores for each age: 28 individuals in 5th grade, 24 individuals in middle school (7th-9th
showing performance within the norm in syntax and phonology. In order to avoid surface-
grade), and 16 adults aged over 21.
dyslexia-like reading that resulted from lack of sufficient exposure to reading, we only
included participants who were in fifth grade and higher, and who had effective classroom
Methods
instruction. Eleven of the participants were in fifth or sixth grade, four were in middle
school, and two were adults. All of them had Hebrew as their mother tongue, and one was
Reading aloud. The route the participants used for reading aloud was assessed using a task
bilingual and had both Hebrew and English as mother tongues. They had no hearing
of reading aloud of single words. The list included 340 Hebrew words, 220 irregular words
impairment, and none of them had a history of neurological disease or head trauma that
with irregularity of an ambiguous consonant or silent letters, 140 of them without a
might have led to acquired dyslexia. As can be seen in Table 1, some of the participants
potentiophone and 80 with potentiophones, and 80 relatively-regular potentiophones.
received remedial teaching within or outside school.
Words were defined "relatively-regular" when they did not include irregularity of
Table 1
them relatively-regular rather than regular because they were still, like all Hebrew words,
ambiguous letters, silent vowel letters, or vowel letters with irregular sound. We called
Background information on the participants with developmental surface dyslexia
underspecified for vowels and stress. Sixteen of the relatively-regular words without
Participant
Age
Grade
Gender
Handedness
potentiophones included the regular conversion of vowel letters, and a sound for
SH
GL
OF
YR
TM
NT
OM
BZ
AS
OS
AK
AM
AL
KR
NF
IR
YD
10;8
10;10
11;2
11;0
12;0
12;8
14;10
43
11
11
13;9
10;7
11
11
14;5
15;10
21
5
5
5
5
6
6
8
adult
5
5
8
5
5
5
8
9
adult
M
F
M
M
F
M
M
M
M
F
M
F
M
F
M
M
F
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
L
R
Remedial
teaching
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
Control groups. A total of 68 individuals without reading or language impairment
underrepresented vowels, which is usually the preferred conversion. The list also included
40 relatively-regular words without potentiophones, which were compared to the irregular
and potentiophonic words.
In addition, in order to assess their ability to read via the sublexical route, five of the
participants (who were still accessible for additional testing) read a list of 30 pronounceable
nonwords (from TILTAN screening test, Friedmann and Gvion, 2003). Twenty of these
nonwords were presented with points indicating the voweling, and ten were unpointed (in
these unvoweled words, when no vowel letter was present, each vowel the participant chose
was accepted as correct). A third of the nonwords was created by substitution of a single
letter in existing words, a third by addition or substitution of the leftmost letter in an
existing word, and another third was created by transposition of middle letters of an
existing word.
Lexical decision. In order to test whether the participants could use the orthographic input
participated as control participants. They were tested with the same tests in order to assess
lexicon even if they read the words aloud via the sublexical route, we used a lexical
the normal level of performance in each test. Because the participants with surface dyslexia
selection task. The task included 75 pairs of letter sequences. Each pair included a word
were of three age groups, 5th-6th grade, middle school, and adults, we administered the tests
10
Developmental surface dyslexias
spelled correctly, and its pseudohomophone (knife-nife for a relevant example in English).
11
Developmental surface dyslexias
Statistical analysis of comparison to the control group. In order to determine for each score
The participants were asked to circle the existing word (the correctly spelled word) in each
of each participant in each test whether it was within the normal range, we compared the
pair.3 The target words included irregular words (chef-shef, key-kee), and words with a
score with the score of the relevant control group. Scores of participants in 5th-6th grade
homophonic letter (cinema-sinema). (Because more than half of the letters in Hebrew, 13 of
were compared to the scores of controls in 5th grade. Scores of participants in 7th-9th grade
the 22 letters, can be mapped onto the same sound as another letter, most of the words have
were compared to the middle school control group, and the scores of the two adults were
a pseudohomophone, and most of the words need orthographic-lexical information for
compared to the adult control group. The comparison was done using Crawford and
correct selection. See Appendix A.)
Howell’s (1998) t-test for the comparison of a single participant to a control group. For
each task and each age group we found the cut-off point beyond which the number of errors
Semantics. For the assessment of the comprehension of homophones and potentiophones
was already significantly larger (p < .05) than the number of errors in the control group.
we used a task with triads of written words. The task included 40 triads, each triad
including a target word and two words – one word was associated semantically with the
target word, the other word was a homophone or potentiophone of the associated word. The
Results
Reading aloud
participants had to choose the word which was semantically associated with the target
The results of the reading aloud task, presented in Table 2, clearly indicate that the
word. For example, for the target word lettuce, we gave the words cabbage and near, which
participants had surface dyslexia. They had significant difficulties in reading aloud of the
; /kruv/-/karov/), and the participant had to choose
target irregular and potentiophonic words, whereas they read the relatively-regular words
cabbage, which was semantically related to the target word lettuce. (A possible example for
better. Each of the participants had significantly more errors than their matched control
English would work on the potentiophones bear and beer – the participant would be asked
group (for the two adults, t(15) > 11, p < .001; for the four participants in middle school,
for the target alcohol to choose between bear and beer).
t(23) > 6, p < .0001; for the children in 5-6 grade, t(27) > 3, p < .002).
Naming. To examine the status of the phonological output lexicon of our participants, we
regularization, of reading with the incorrect vowel when the vowel was not represented,
are potentiophones in Hebrew (
-
Their reading errors were characteristic of surface dyslexia: they were errors of
also included a task of naming 100 color pictures of objects (SHEMESH, Biran and
reading with the incorrect mapping to sound of sound-ambiguous letters, and incorrect
Friedmann, 2004, 2005, 2006; Friedmann and Biran, 2003). The participants were
stress position (see Appendix B for error examples).
presented with a picture and were asked to name it aloud. We collected the responses,
Participants’ reading of irregular and potentiophonic words was significantly poorer than
including hesitations and self corrections. This task was administered to 15 of the 17
their reading of the relatively regular words, z(16) = 3.5, p = .0005.4 The participants made
participants.
more errors when the target irregular word had a potentiophone than when it did not. This
held for the group level, z(15) = 2.97, p = .003, and individually for 14 of the participants.
3
We preferred to use a lexical selection task for a word and its pseudohomophone over lexical decision of
single items because on the basis of an earlier assessment (Lukov and Friedmann, 2006), individuals with
surface dyslexia who perform flawlessly or almost flawlessly on lexical selection sometimes fail on lexical
decision. This, we believe, results from the inclination or custom, when encountered with a letter string, to
read and sound-out via the sublexical route. In the case of lexical decision of a pseudohomophone this
tendency yields an existing word and thus leads to acceptance of the pseudohomophones as a word. However,
such strategy cannot be employed when two items are presented, which both lead to the same sound. In this
case, the reader is forced to consult the orthographic input lexicon. When this lexicon is available, lexical
selection is successful.
The older participants made the fewest errors on the irregular words without potentiophone,
4
The comparison between conditions within the surface dyslexia group was done using the nonparametric
Wilcoxon signed ranks test. All these comparisons were also done with the parametric Student t-test, with
similar results.
12
Developmental surface dyslexias
possibly because they learned to block or avoid non-lexical responses.5
Gvion, 2001, 2005; Friedmann and Rahamim, 2007) so we did not include the words in
Percentage error in reading aloud of irregular and relatively-regular words, and of words
with and without potentiophones
SH
GL
OF
YR
TM
NT
OM
BZ
AS
OS
AK
AM
AL
KR
NF
IR
YD
Control groups
5th grade
Middle school
Adults
1
Developmental surface dyslexias
performance in the study. AK also had a mild letter position dyslexia6 (Friedmann and
Table 2
Participant
13
Irregular with
potentiophone
Irregular no
potentiophone
Relativelyregular with
potentiophone
Total
irregular /
potentiophone
Relativelyregular no
potentiophone
37
39
29
56
50
56
37
21
25
44
20
23
20
21
46
11
14
28
31
18
48
37
50
29
10
18
37
18
31
13
21
28
7
3
45
47
34
56
60
39
46
38
56
28
45
32
31
27
23
20
35
38
25
52
49
51
35
23
26
44
22
33
20
24
33
14
12
8
8
8
11
9
0
3
0
11
3
5
11
5
3
3
6
1
1.5
0.9
0
4.3
2.2
0.3
7.8
3.8
2.2
5.0
2.5
1.0
1.6
0.3
0.1
NT was not tested on regular potentiophones
which he made letter migration errors in any analysis.
Table 3
Number of other errors in reading the 340 word list
Participant Morphological
error
SH
0
GL
0
OF
0
YR
0
TM
0
NT
0
OM
0
BZ
0
AS
0
OS
0
AK
0
AM
0
AL
0
KR
0
NF
0
IR
0
YD
0
Semantic
error
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Transposition
error
0
5
1
4
1
0
0
0
2
1
5
1
0
1
0
1
3
Neglect
error
0
0
0
0
5
0
0
0
0
0
0
0
0
0
0
0
0
Visual
error
0
0
5
3
1
1
0
0
2
1
0
0
1
0
0
0
0
Other
error
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Nonword reading. The five participants who read the nonword list, TM, OM, BZ, AM, and
YD, showed unimpaired reading of nonwords. OM and YD made no errors in their
The surface dyslexia of 15 of the participants was pure, with very few errors that did not
nonword reading; TM, BZ, and AM had between one and two migration errors which they
result from reading via grapheme-to-phoneme conversion, as seen in Table 3. Notice that
immediately corrected, in the nonwords in which a transposition created an existing word.
none of the participants produced semantic or morphological paralexias, indicating that
The good reading of nonwords indicates that the participants tested had intact sublexical
they were not reading aloud via the semantic system. TM and AK had developmental
route.
attentional dyslexia in addition to developmental surface dyslexia, but because the words
The following sections present the results of the lexical decision and comprehension
were presented to them separately, a single word at a time, this did not affect their
tasks. Table 4 summarizes the performance of each of the participants on the three levels -
5
The regular words with potentiophones were read as poorly as the irregular words with potentiophones, and
for some of the participants even significantly more poorly, as a result of the relative regularity and frequency
of each target words and its potentiophone in the two word groups tested (see Lukov and Friedmann, 2006 for
the detailed examination of the effect of frequency, regularity, and type of irregularity on reading aloud of
various words).
6
This was diagnosed using a list of 232 words with lexical potential for middle letter migration, in which he
made 31 middle letter migration errors (13.4%), and a screening test that included 64 migratable words, in
which he made 9 middle migrations (14%) (both tests from the TILTAN test battery, Friedmann and Gvion,
2003).
14
Developmental surface dyslexias
reading aloud, which was presented in this section, and lexical decision and
15
Developmental surface dyslexias
Lexical decision
comprehension, which will be presented in the next sections. The bottom rows of Table 4
The participants differed with respect to their ability to decide which of two letter strings
include the threshold for each task above which the number of errors of a dyslexic
was a word spelled correctly, as seen in Table 4. Whereas nine of the participants
participant is significantly larger (Crawford and Howell’s (1998) t-test, p < .05) than the
performed within the normal range in this task (p > .05 for the comparison of each of them
age-matched control group. (For example, the adults control group had an average of 1.0%
with
errors in reading aloud irregular/potentiophonic words, with SD of 0.9%. For these data,
(t > 6, p < .001).
their controls), eight performed
significantly poorer than their controls
given 16 participants in this control group, the lowest score that would be significantly
different from the control would be 2.7% errors, using Crawford and Howell’s (1998) t-test,
Homophone and potentiophone comprehension
The assessment of homophone/potentiophone comprehension showed that some of the
and this is presented in Table 2).
participants performed well in this task, indicating preserved access to semantics, whereas
others did poorly. As seen in Table 4, six of the participants performed within normal limits
Table 4
Percentage errors in tasks of the three levels: reading aloud of irregular words and potentiophones,
lexical selection, and homophone/potentiophone comprehension. The shaded cells include
performance that is significantly poorer than that of the relevant control group.
Participant
Grade
Deficit location
Reading aloud
Lexicon Semantics
in the homophone selection task, whereas the other participants performed significantly
poorer than their control groups (p < .05), five of them performing at chance level on this
task.
group
SH
GL
OF
YR
TM
NT
OM
BZ
5
5
5
5
5
5
middle
adult
Orthographic lexicon
Orthographic lexicon
Orthographic lexicon
Orthographic lexicon
Orthographic lexicon
Orthographic lexicon
Orthographic lexicon
Orthographic lexicon
35
38
25
52
49
51
35
23
24
24
11
12
38
631
12
9
41
23
15
27
58
48
8
14
AS
OS
AK
5
5
middle
Orthographic lexicon output
Orthographic lexicon output
Orthographic lexicon output
26
44
22
4
4
1
36
30
10
4
3
1
3
2
0
5
5
5
5
0
1
AM
5
Interlexical
33
AL
5
Interlexical
20
5
Interlexical
24
KR
middle Interlexical
33
NF
middle Interlexical
14
IR
adult
Interlexical
12
YD
Thresholds for performance significantly different from the control groups
5th graders
10
Middle school
5
Adults
2.7
1
5
4
1
14
7.5
3
NT received a different task in which he made lexical decisions for single words rather than selection
between two options. This score is the percentage of pseudohomophone which he accepted as words.
Naming
The results of the naming task are reported in Table 5. The naming performance of 16 of
the 17 participants was within the normal range, with performance ranging between 92 and
100 items named correctly out of 100 items, indicating intact lexical access and retrieval.
Especially relevant for surface dyslexia, in which some individuals showed impaired
phonological output lexicon, the naming ability of the participants in this study indicates
that they had no impairment at the phonological output lexicon. None of the participants
produced a phonemic paraphasia, indicating also an intact phonemic output buffer for all
the participants.
One participant, AS, performed below the normal range, with 88% correct naming,
which might indicate a deficit in lexical retrieval as well. Unlike previously reported
individuals with acquired surface dyslexia, the pattern of his errors and other responses in
the naming task did not indicate a deficit in the phonological output lexicon, which is
usually manifested in phonologically-related paraphasias. His errors were close semantic
paraphasias, hesitations, and don’t know responses, and only one of his paraphasias was a
formal paraphasia, which was not only phonologically, but also semantically, related to the
16
Developmental surface dyslexias
target word. AS’s response pattern is not characteristic of a deficit in the phonological
lexicon itself, because a deficit at this level is expected to also yield phonemic paraphasias.
According to his error pattern, AS’s mild lexical retrieval difficulties stem from a deficit
either in the semantic lexicon, or in the access from the semantic lexicon to the
phonological output lexicon – according to Butterworth (1989) and Caramazza and Hillis
(1990), when there is no access to the phonological representation of the target word, a
word which is semantically related to it, whose phonological representation is available,
17
Developmental surface dyslexias
Input surface dyslexia: a deficit at the lexicon or in the access to it?
We ascribed the deficit of the first group to an impairment in the orthographic input
lexicon or in the access to it. In order to decide between these two possibilities, we further
tested the ability of one of the participants in the first group, BZ, to perform a lexical
decision task for both written and orally spelled sequences. If it is only the access from the
orthographic-visual analysis system to the orthographic input lexicon that is impaired,
whereas the orthographic input lexicon is intact, we would expect failure in the written
might be produced instead. The fact that he had frequency effect on naming (rpb = 0.2,
lexical decision but success in the orally spelled one, because orally spelled words access
p = .03) further supports a deficit in the access to the phonological output lexicon rather
the orthographic input lexicon from another route and not through the visual analyzer.
than a deficit in the semantic lexicon (Jescheniak and Levelt, 1994). It might be interesting
to note that AS also had a deficit in the access from the orthographic input lexicon to the
phonological output lexicon, so his deficit might be a general difficulty accessing the
phonological output lexicon. (This is unlike the other 8 individuals in the current study who
had a deficit in the connection of the orthographic input lexicon to the phonological output
lexicon, whose access to the phonological output lexicon from semantics was unimpaired).
The written lexical decision task administered to BZ included 108 sequences, 54 words
and 54 pseudohomophones. The orally spelled lexical decision comprised 34 words,
including 17 existing words and 17 pseudohomophones. The results showed that BZ
performed poorly on both tasks. He accepted 65% and 33% of the pseudohomophones as
existing words, respectively. This suggests that BZ’s orthographic input lexicon was
Performance on naming 100 objects
SH
GL
OF
YR
OM
BZ
AS
OS
AK
AM
AL2
KR
NF
IR
YD
performance.7
existing words in the oral and written task respectively, and rejected 18% and 4% of the
Table 5
Participant
However, if the lexicon itself is impaired, both modalities should yield impaired
Correct
responses
93
96
95
92
96
100
88
96
95
97
96
92
99
100
96
Don’t
know
1
1
3
2
2
1
1
5
Paraphasia
semantic formal1
1
1
2
4
4
5
2
1
1
1
Correct naming following
long
semantic
hesitation
paraphasia
3
2
1
1
Another factor that might speak to a deficit in the orthographic input lexicon rather than
impaired access to it, is the effect of frequency. We expect that the orthographic input
lexicon would be affected by frequency, with higher probability of retrieving frequent
written words, whereas a pre-lexical impairment of access to the orthographic input lexicon
3
3
2
2
3
1
2
impaired.
should not be affected by lexical factors such as frequency. For this reason we analyzed the
1
effect of frequency on the reading aloud of all participants with input surface dyslexia. This
was done in two ways: Firstly, we estimated the written frequency of the irregular words in
0
the 340 word list using Google search, and compared the accuracy in reading the 20 most
1
1
1
on the list. For each of the individuals, an effect of frequency was found, with higher
frequent irregular words to the reading of the 20 irregular words with the lowest frequency
accuracy in reading the more frequent words. The second way in which we assessed
4
1
All the formal paraphasias were phonologically and semantically related to the target.
2
AL’s don’t know response and his correct response following hesitation also included a definition of the target.
7
It is, of course, possible that both access routes to the lexicon are impaired, in which case no differential
diagnosis can be made between impaired lexicon and impaired access to the lexicon from all access routes.
18
Developmental surface dyslexias
19
Developmental surface dyslexias
frequency effect was via examination of the relative frequency of a target word and its
potentiophone. We asked 50 individuals without reading disorder to evaluate the relative
frequency of the 160 target words with potentiophones from the 340 words list, compared
to their potentiophones. We then selected the 89 potentiophone pairs which yielded a
significant preference for one of the potentiophones8. The analysis of reading accuracy
The naming assessment suggests that the marked tendency to read via grapheme-tophoneme conversion does not result from a deficit at the phonological lexicon, at least for
16 of the 17 participants, who did not have lexical retrieval deficits or phonemic
paraphasias.
showed that each of the participants made more errors on the 37 target words which were
DISCUSSION
less frequent than their potentiophones, compared to the number of errors on the 52 target
words which were more frequent than their potentiophones. These two analyses, which
point to the effect of frequency on reading aloud of each of the individuals with input
surface dyslexia, indicate a deficit in the lexicon rather then the access to it.
Summary - subtypes and functional localization of the deficits
The results reported above indicate that the participants can be classified into three
groups, each with a different subtype of developmental surface dyslexia. The first group,
which includes SH, GL, OF, YR, TM, NT, OM, and BZ, showed impaired reading aloud,
impaired lexical decision, and impaired homophone and potentiophone comprehension. We
suggest that the participants in this group have an impairment that relates to the
orthographic input lexicon, most probably in the lexicon itself. The individuals in the
second group, AS, OS, and AK, had impaired reading aloud, impaired homophone/
potentiophone comprehension, and good lexical decision. This pattern suggests a
functioning and accessible orthographic input lexicon, with impaired output from it to
semantics and to the phonological output lexicon. The third group, which included AM,
AL, KR, NF, IR, and YD, showed impaired oral reading of irregular words and
potentiophones, but at the same time had normal performance in lexical decision and in
homophone/potentiophone comprehension. This pattern can be ascribed to intact
orthographic input lexicon, which also has intact access to the semantic system, but
impaired access to the phonological output lexicon.
The main finding of the current study is the identification of three subtypes of
developmental surface dyslexia. These subtypes differ with respect to the locus on the
lexical reading route that is impaired, all leading to reading via the sublexical route, but
with different performance pattern with respect to orthographic-lexical knowledge and
comprehension.
The first subtype of developmental surface dyslexia, input surface dyslexia, was a deficit
that related to the orthographic input lexicon. As a result, the eight individuals who had this
type of developmental surface dyslexia were forced to read via the grapheme-to-phoneme
conversion route, and therefore made regularization and potentiophone errors in reading.
Because the orthographic input lexicon was inaccessible to them, they also failed on lexical
decision, and given that the orthographic input lexicon was inaccessible, they could not
reach the semantic system from reading, and hence made errors in comprehension of
homophones and potentiophones. Frequency effects on reading aloud indicate that the
deficit of the participants in this group was in the orthographic input lexicon rather than in
the access to it. For one of the participants in this group, this conclusion was supported by
his poor performance also when the words were spelled aloud to him.9
The second subtype of developmental surface dyslexia that was witnessed in the current
study, orthographic lexicon output surface dyslexia, was characterized by unimpaired
access to the orthographic input lexicon, but impaired connection from it to the next stages:
phonological output lexicon and the semantic system. As a result, the three individuals who
had this surface dyslexia subtype read aloud via the sublexical route, and hence made
9
8
We counted a potentiophone as significantly more frequent than its counterpart when the number of judges
who chose it as the more frequent was larger than twice the number of judges who chose the counterpart plus
the number of judges who said they were equi-frequent.
When discussing developmental surface dyslexia, it is hard to imagine how an intact orthographic input
lexicon would develop when the access to it from visual analysis is impaired. Thus, it is unlikely to find such
a deficit in developmental surface dyslexia, of impaired access to the orthographic input lexicon, but with
intact orthographic input lexicon. Such a deficit might be more clearly manifested in acquired dyslexia.
20
Developmental surface dyslexias
regularization and potentiophone errors, but still could identify the correct spelling of
21
Developmental surface dyslexias
orthographic input lexicon can develop even when its output is impaired, and that
written words, and choose between the correct spelling of a word and its
developmental dyslexias can exhibit selectivity in impairment, similarly to acquired
pseudohomophone. However, because the access from the orthographic input lexicon to the
dyslexias. It is interesting to note that the selective impairment of the participants reported
semantic system was impaired, they could not use their intact lexical knowledge to access
in the current study is even more selective than that reported for adults with acquired
the correct meaning of homophones and potentiophones, and had to access meaning in an
surface dyslexia. Firstly, whereas for some participants with acquired surface dyslexia the
indirect way: they read the words via the sublexical route, and the input to semantics was
sublexical route was not completely intact (Coltheart, 2006), the five participants in the
the phonological result of this conversion. This led to failure in the homophone/
current study who were tested in nonword reading, read them well, indicating a good
potentiophone comprehension task.
sublexical route.
The third subtype of developmental surface dyslexia identified in this study, interlexical
Furthermore, apart from surface dyslexia that results from a deficit at the orthographic
surface dyslexia, resulted from disconnection between the orthographic input lexicon and
input lexicon, the two subtypes that were reported in the literature included either a deficit
the phonological output lexicon. Because of this disconnection, the six individuals with this
to the phonological output lexicon or a semantic deficit (Ellis et al., 2000). Whereas the
subtype of developmental surface dyslexia had to read via the sublexical route, which
individuals reported in studies of acquired surface dyslexia (Bub et al., 1985; Graham et al.,
caused regularization and potentiophone errors in reading aloud, but when they did not
1994; Howard and Franklin, 1987; Kay and Ellis, 1987; Kay and Patterson, 1985; McCarthy
have to reach the phonological output lexicon, in tasks of lexical decision and
and Warrington, 1986; Patterson and Hodges, 1992; and Shallice et al., 1983) had general
comprehension, they performed at a normal level. That is to say, because they had access to
lexical or semantic-conceptual deficits, not only in reading, the participants in the current
the orthographic input lexicon, they could identify the correct spelling of written words,
study had no aphasia, and only one of them had mild naming difficulties. This leads to an
and because they had access from the orthographic input lexicon to the semantic system,
important difference between the subtypes of surface dyslexia described in the literature
they could also access the meaning of lexical items from the orthographic input lexicon,
until now, and the subtypes we describe in the current study. In the current study two new
and therefore their comprehension was intact even for homophones and potentiophones.
subtypes were found, which involved the connections between components rather than a
Their impairment was in the connection between the orthographic and the phonological
deficit to the components themselves.10 One subtype results from a deficit in the
lexicons rather than in the phonological output lexicon itself, as indicated by their good
connections between the orthographic input lexicon and both the semantic system and the
naming performance. One other pathway could theoretically be employed by the
phonological output lexicon, the other subtype involves a deficit in the connection between
participants with the interlexical disconnection – because the semantic system is accessible
the orthographic input lexicon and the phonological output lexicon. The phonological
to them, they could have proceeded to oral reading via the pathway Semantics
output lexicon was not impaired, and nor was the semantic system. Thus the results confirm
Phonological output lexicon. However, the finding that none of these participants made
the existence of two new subtypes of surface dyslexia, which were predicted theoretically
even a single semantic or morphological paralexia indicates that they did not use this route
from the dual-route reading model, but have not been attested until now.
for oral reading. A possible conclusion is that the route for reading aloud via the semantic
The identification of subtypes of developmental surface dyslexia suggests an interesting
system is only employed as a last resort, when neither the direct route nor the sublexical
route is available for reading. This is the case in deep dyslexia, where this is the only route
available, and reading via it yields many semantic and morphological errors.
The fact that this distinction was found in developmental dyslexia, suggests that the
10
We do not think that the fact that subtypes of acquired surface dyslexia reported until now involved damage
to the lexicon or the semantic system whereas the subtypes in the current study of developmental surface
dyslexia did not involve lexical and semantic impairment, relates to some deep difference between acquired
and developmental dyslexia. There is no reason to assume that the two types of surface dyslexia we described
here that result from damage to the connections from the orthographic input lexicon cannot occur in acquired
surface dyslexia as well.
22
Developmental surface dyslexias
angle to look at two related debates concerning developmental dyslexia: whether the
23
Developmental surface dyslexias
characteristics of reading in developmental surface dyslexia that emerge from the current
underpinnings of developmental dyslexia are phonological, and whether developmental
study are remarkably similar to the pattern of reading in acquired surface dyslexia
dyslexia can be described in terms of selective deficits to a reading model similar to that
described in the literature (Patterson et al., 1985) and for acquired surface dyslexia in
suggested for skilled adult readers, and hence with types similar to those identified in
Hebrew (Gvion and Friedmann, 2001). These results thus join a growing body of studies
acquired dyslexia. In order to answer the first question, consider what individuals with
that provide robust evidence for the existence of subtypes of developmental dyslexia, which
developmental surface dyslexia of all three types can do, i.e., what is the skill that they use
show striking similarity to subtypes of acquired dyslexia. This has been reported for
all the time for reading aloud. What they do is analyze the input letter sequence, segment it,
developmental surface dyslexia (Broom and Doctor 1995a; Castles et al., 2006; Castles and
convert graphemes to phonemes, and then combine the phonological segments and produce
Coltheart, 1993, 1996; Coltheart et al., 1983; Judica et al., 2002; Masterson, 2000; Temple,
an integrated phonological representation. In other words, children with developmental
1997; Valdois et al., 2003), developmental phonological dyslexia (Broom and Doctor,
surface dyslexia are very proficient exactly in phonological skills, and their deficit resides
1995b; Howard and Best, 1996; Temple, 1997; Temple and Marshall, 1983; Valdois et al.,
elsewhere, in the lexical route. As John Marshall (1998) put it, "These children manifest
2003), developmental direct dyslexia (Glosser et al., 1997), developmental deep dyslexia
reading difficulties … precisely because they have acquired the core skills that Shaywitz
(Stuart and Howard, 1995; Siegel, 1985; Temple, 1988, 2003), as well as for developmental
claims are impaired in developmental dyslexia". This finding emphasizes that
peripheral dyslexias: developmental letter position dyslexia (Friedmann and Rahamim,
developmental dyslexia is not generally a phonological deficit, and that claims about
2007), developmental attentional dyslexia (Rayner et al., 1989), and developmental neglect
phonological bases for developmental dyslexia should be made scrupulously, and with
dyslexia (neglexia, Friedmann and Nachman-Katz, 2004; Nachman-Katz and Friedmann,
reference to specific subtypes. The general claim that developmental dyslexia results from a
2007). (For a comprehensive survey of this literature see Brundson et al., 2002; Castles et
phonological deficit or from poor phonemic awareness (Frith, 1997; Goswami, 2002;
al., 2006; Castles and Coltheart, 1993; Castles et al., 1999; Temple, 1997).
Marshall CM et al., 2001; Snowling, 1998; Stanovich, 1988) might be true for some types
Such wealth and diversity of subtypes of developmental dyslexia cannot be accounted
of developmental dyslexia (specifically, phonological and deep dyslexia), but is not
for by a single deficit underlying developmental dyslexia, but it can be clearly interpreted
applicable to other subtypes. Developmental dyslexias do not necessarily come with poor
using the dual route model of reading, as resulting from deficits to various components of
phonemic awareness and not all of them result from poor phonemic awareness (Castles and
the model, similar to subtypes of acquired dyslexia (Castles et al., 2006; Castles and
Coltheart, 2004; Friedmann and Rahamim, 2007) or a phonological deficit (see McCloskey
Coltheart, 1993; Coltheart et al., 1983; Marshall, 1984b; Temple, 1997).
and Rapp, 2000 for a discussion). Some studies that directly tested phonemic awareness in
Another result of this study is the way surface dyslexia manifests itself in a highly
children with developmental surface dyslexia actually found that these children performed
irregular language, Hebrew. The discussion of surface dyslexia in English, for example,
above average in meta-phonological tests (Lukov and Friedmann, 2004; Valdois et al.,
focuses on irregular words that include a grapheme with two possible conversions to
2003). Thus, whereas phonological deficits and deficits in the phonological-sublexical route
phoneme, which occurs in its less frequent conversion, or words with silent letters (such as
might cause considerable difficulties in reading, not all reading difficulties result from
sword, island, receipt, buffet, sew, listen). In Hebrew, many such words exist, because 9 of
phonological deficits.
the 22 letters have ambiguous conversion to phonemes. However, ambiguous letters are not
Relatedly, the current research indicated that pure surface dyslexia exists in a
the only source of ambiguity in grapheme-to-phoneme conversion. The underspecification
developmental form, and that subtypes can even be identified within it, subtypes which can
of vowels in the orthography, and the lack of marking for stress position (in the absence of
be readily accounted for within the framework of the dual-route model for reading. The
default stress), create an orthography in which no word is regular – namely, there is no
24
Developmental surface dyslexias
written word that can be unambiguously converted to phonemes. The findings of the
25
Developmental surface dyslexias
West, 1989), and as a result do not establish a rich orthographic input lexicon. This, in turn,
current study indicated that in such orthography not only do ambiguous letters get the
results in “surface-dyslexia-like” reading (Friedmann and Gvion, 2002; Friedmann and
incorrect conversion to phonemes, but, also, incorrect vowel pattern is chosen for the whole
Nachman-Katz, 2004; Friedmann and Rahamim, 2007; Nachman-Katz and Friedmann,
word in the absence of vowel specification, sometimes resulting in a nonword and
2007; Rahamim and Friedmann, in press). The administration of lexical decision and
sometimes in another existing word. Another important factor for reading in surface
homophone comprehension tasks in addition to oral reading can help in determining
dyslexia, at least in Hebrew, is the potentiophonic status of the target word. When the letter
whether the child has surface dyslexia or whether it is just an impoverished orthographic
sequence can be read via grapheme-to-phoneme conversion as another existing word, such
input lexicon secondary to another dyslexia. If the deficit is found to be located at the
errors occur even when the word is relatively-regular. For example,
orthographic input lexicon, other ways will be needed to make the decision, but if the
and
can both be
converted to /k/, and the letter can be converted to /v/, /u/, and /o/. Thus, the word
deficit is found to be located elsewhere, in the output of the orthographic input lexicon to
(KMOT, wake-up-plural, /kamot/), although relatively-regular, when read via the
the phonological output lexicon or to semantics, this will suggest that it is indeed a genuine
sublexical route, can be read as the word
surface dyslexia, and not a phenomenon secondary to reading avoidance.
(QMOT, quantity, /kamut/). The special
susceptibility of potentiophones to reading errors results from the fact that when a reader
With respect to treatment, different treatment plans should be applied to the different
reads a potentiophone via the sublexical route incorrectly, she cannot know that she has
subtypes of surface dyslexia – treatment for individuals with a deficit at the orthographic
made an error because the result is an existing word (for the effect of frequency and
input lexicon should include improving the operation of this lexicon (see Coltheart and
regularity on potentiophone errors see Lukov and Friedmann, 2006). Potentiophones are
Byng, 1989; Weekes and Coltheart, 1996), and establishing robust lexical entries in this
especially helpful in the detection of surface dyslexia, because errors cannot be detected
lexicon by means of mnemonics for example. However, if the orthographic input lexicon is
and corrected by the reader, and because, unlike homophones, even reading aloud can
intact and functioning, the treatment should be directed elsewhere. For example, the work
already indicate a deficit in reading via the lexical route. Homophones, on the other hand
with individuals who have access to the orthographic input lexicon but cannot access the
require additional comprehension tasks.
phonological output lexicon and semantics should be directed at improving these
The identification of subtypes of developmental surface dyslexia is interesting and
connections, and for individuals who have surface dysgraphia alongside this type of surface
important not only for its theoretical implications. It also has immediate implications for
dyslexia, reading for monitoring of writing can be trained. For those individuals who read
diagnosis and treatment. With respect to diagnosis of developmental surface dyslexia, the
aloud incorrectly via the sublexical route but who understand words correctly via the route
current results suggest that it is not enough to detect that an individual reads via the
from the orthographic input lexicon to the semantic system, the advice should be – do not
sublexical route by assessing her performance in reading aloud. Tasks involving lexical
read aloud.
decision and homophone/potentiophone comprehension are required to discover the exact
locus of impairment in the reading process.
To summarize, developmental surface dyslexia has several faces. The current study
identified three groups of individuals who had different subtypes of developmental surface
The distinction between different loci that can cause reading via grapheme-to-phoneme
dyslexia. All subtypes resulted from an impaired lexical route, which forced reading via
conversion can also be used to discern developmental surface dyslexia from impoverished
grapheme-to-phoneme conversion, causing difficulties in reading irregular words and
orthographic lexicon that results from limited exposure to reading. In many cases children
potentiophones, but they differed with respect to the locus of impairment within the lexical
with other types of dyslexia, such as peripheral dyslexias, avoid reading as much as they
route, and, as a result, in the manifestation of the deficit in lexical decision and
can (see Cunningham and Stanovich, 1998; Share, 1999; Stanovich, 1986; Stanovich and
comprehension.
26
Developmental surface dyslexias
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31
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APPENDIX A
APPENDIX B
Ambiguous grapheme-phoneme and phoneme-grapheme correspondences in Hebrew
Examples for errors the participants made in reading aloud
Target
Target
Target
word
letters
pronunciation translation
pronunciation translation
Potentiophone
QTR
keter
crown
katar
locomotive
error
KOB
kove’a
determines
kova
hat
Ambi-phoneme letters in Hebrew
Hebrew letter
Phonemes
Target
Response
Response
A
vb
B
QIsA
kise
chair
kisa
covered
aeø'
H
BRIQH
brexa
pool
brixa
run-away
vuo
O
LMROT
lamrot
although
limrot
to-pluck
i y (a e ei)
I
QTF
katef
shoulder
kataf
picked
kx
Q
BL DIO
Bil’adav
baladiyo
-
MROX
maruax
withouthim
spread
marux
-
P
RAS
rosh
head
ra'ash
noise
S
KISOA
kishu
zucchini
kiso'a
-
SMLH
simla
dress
shimla
-
ASMX
esmax
ashmax
-
Transcript
CINOR
cinor
I-will-behappy
pipe
cinur
-
a
H A
HTLBtH
hitlabta
pondered
hitlavata
-
' (glottal stop)
H A
TXBR
texaber
-
OB
x
XQ
LNKOT
lenakot
she-willconnect
to-clean
taxbar
v
lankut
-
t
Tt
k
KQ
SRtTM
saratetem
sertatem
s
Ss
TB t
tiv'at
you-plscratched
You-willkick
PRsIT
parsit
' a ea
pf
s sh
Regularization
error
Ambiguous
letter error
Ambi-letter phonemes in Hebrew
Letters
Potentiophone Comments
response
spelling
Transcript
a e (ø o i) ‘(glottal stop)
Phoneme
32
Vowel error
Farsi
taba'at
ring
persit
-
potentiophone
can be read as sh
or s (sh is the more
frequent conversion)
can be read as sh
or s
can be read as o,u,or
v
can be read as b or
v
Error in
unrepresented vowel
Error in
unrepresented vowels
and ambiguous vowel
letter
Error in
unrepresented vowels
potentiophone+ambig
uous letter+ error in
unrepresented vowels
Error in
unrepresented vowels