Investigating the Double-Deficit
Hypothesis in Greek
Findings From a Longitudinal Study
Journal of Learning Disabilities
Volume 42 Number 6
November/December 2009 528-547
© 2009 Hammill Institute on
Disabilities
10.1177/0022219409338745
http://journaloflearningdisabilities
.sagepub.com
hosted at
http://online.sagepub.com
Timothy C. Papadopoulos
University of Cyprus
George K. Georgiou
University of Alberta, Edmonton
Panayiota Kendeou
McGill University, Montreal
This study examined longitudinally the double-deficit hypothesis in Greek, an orthographically consistent language, following a group of children from kindergarten to Grade 2. Four groups were formed on the basis of two composite scores of
phonological and naming-speed criterion measures: a double-deficit group (DD; n = 17), a phonological deficit group (PD;
n = 33), a naming deficit group (ND; n = 33), and a control group exhibiting no deficits (CnD; n = 159). The four groups
were identified in Grade 1, and they were compared retrospectively in kindergarten only on the criterion measures, and in
Grades 1 and 2 on measures of word-reading fluency and accuracy, orthographic processing, and passage comprehension.
The effects of verbal and nonverbal ability, age, gender, and parental education were controlled among the groups. Results
showed that the DD group exhibited greater dysfunction in reading and orthographic processing compared to the singledeficit and CnD groups. Also, although the three deficit groups were not easily differentiated in kindergarten, their differences
were maximized in Grade 1 and retained in Grade 2. The type and severity of reading deficits found in the ND group were
mostly associated with naming speed at both the word- and text-reading levels, deficits that persisted across development.
The PD group showed mostly deficient orthographic and poor decoding skills that improved across development. Implications
of the findings for the double-deficit hypothesis in languages with transparent orthographies are discussed.
Keywords: reading difficulties; double-deficit hypothesis; orthographically consistent languages; longitudinal analysis
T
o date, there is little disagreement that phonological
awareness, broadly defined as the ability to perceive
and manipulate the sounds of spoken words, is of paramount importance to reading development and at the
same time a bottleneck to efficient phonological recoding (e.g., Bryant, Bradley, Maclean, & Crossland, 1989;
Hulme, Snowling, Caravolas, & Carroll, 2005; McBrideChang, & Kail, 2002; Share, 1995; Stanovich, 1992;
Torgesen, Wagner, & Rashotte, 1994; Vellutino, Fletcher,
Snowling, & Scanlon, 2004). However, deficits in phonological awareness alone do not appear to account for all
that is known about the development of reading problems.
As a result, researchers have begun to examine other possible sources of individual differences in reading. Wolf
and Bowers (1999) argued that rapid-automatized-naming
(RAN) speed, defined as the ability to name as fast as
possible visually presented, highly familiar symbols,
528
such as digits, letters, colors, and objects, is a second
core deficit in reading disabilities.
RAN has been shown to be a strong predictor of reading in several alphabetic (e.g., Blachman, 1984; Compton,
2003; de Jong & van der Leij, 1999; Georgiou, Parrila,
& Liao, 2008; Kirby, Parrila, & Pfeiffer, 2003; Lepola,
Poskiparta, Laakkonen, & Niemi, 2005; Savage &
Frederickson, 2005) and nonalphabetic languages (Cheung,
McBride-Chang, & Chow, 2006; Chow, McBride-Chang,
& Burgess, 2005; Ho & Bryant, 1997; McBride-Chang
Authors’ Note: This research was supported by EU-UCY Grants for
Applied Research Projects for Cyprus (No. 8037-16013) to the first
author. Address correspondence to Timothy C. Papadopoulos,
Department of Psychology, University of Cyprus, P.O. Box 20537,
1678 Nicosia, Cyprus; e-mail: [email protected]
Papadopoulos et al. / Double-Deficit Hypothesis in Greek 529 & Kail, 2002), accounting for unique variance above and
beyond general cognitive ability (Badian, 1993), shortterm memory (Parrila, Kirby, & McQuarrie, 2004), articulation rate (e.g., Bowey, McGuigan, & Ruschena, 2005),
letter knowledge (Kirby et al., 2003), and importantly,
phonological awareness (Bowers, 1995; Kirby et al., 2003;
Manis, Doi, & Bhadha, 2000).
The independent contribution of RAN and phonological awareness skills in reading ability has led researchers
to examine if the coexistence of RAN and phonological
awareness deficits results in more severe reading difficulties than do single deficits alone (e.g., Kirby et al.,
2003; Lovett, Steinbach, & Frijters, 2000; Manis et al.,
2000; Schatschneider, Carlson, Francis, Foorman, &
Fletcher, 2002; Wolf & Bowers, 1999; Wolf, O’Rourke,
Gidney, Lovett, Cirino, & Morris, 2002). The doubledeficit hypothesis “places equal importance on the roles
of phonological factors and naming-speed factors for
diagnosis, prediction, and remediation” (Wolf & Obregon,
1997, p. 202). Based on this hypothesis, four separate
groups of individuals have been tested in relevant
research: one with no deficits, two with single deficits on
either RAN or phonological awareness, and one with
double deficits on both phonological awareness and
RAN. It has been shown that the children in the doubledeficit group experience the most severe reading difficulties, followed by the children in either one of the
single-deficit groups (Wolf & Bowers, 1999).
The studies that examined the double-deficit hypothesis provided contradictory findings in support of such
deficit (e.g., Ackerman, Holloway, Youngdahl, & Dykman,
2001; Compton, DeFries, & Olson, 2001; Kirby et al.,
2003; Manis et al., 2000; Schatchneider et al., 2002;
Spector, 2000; Sunseth & Bowers, 2002; Vukovic &
Siegel, 2006; Wimmer, Mayringer, & Landerl, 2000).
The discrepancies can be attributed to three factors.
First, some studies used typically developing children
and examined if they could be assigned to the three
hypothesized deficit groups (e.g., Manis et al., 2000;
Powell, Stainthorp, Stuart, Garwood, & Quinlan, 2007;
Sunseth & Bowers, 2002), whereas other studies used
children with reading disabilities (e.g., Compton et al.,
2001; Lovett et al., 2000). For example, Manis et al.
(2000) found support for the double-deficit hypothesis
after classifying a group of 85 second-grade children
into those with no deficits (n = 50), those with phonological deficits only (n = 13), those with naming-speed
deficits only (n = 14), and those with a double deficit
(n = 8). However, their double-deficit group had word
identification scores ranging from below the 25th percentile
to the 48th percentile, and thus not all the children in this
group had reading problems. On the other hand, Lovett
et al. (2000) classified 166 children (7–13 years old)
with identified reading disabilities into the hypothesized
double-deficit subtypes. Lovett and her colleagues found
that the double-deficit group showed the most severe
impairments on measures of reading, spelling, and arithmetic, followed by the phonological deficit group and
the naming deficit group.
Second, differences may have been brought about
because of the use of different cutoff scores to identify
the groups with deficits. For example, in studies with
typically developing samples of children, Bowers,
Sunseth, and Golden (1999) used the 35th percentile as
a cutoff score, Sunseth and Bowers (2002) the 30th percentile, and Manis et al. (2000) the 25th percentile. In
studies with children with reading disabilities, Lovett
et al. (2000) used the 25th percentile as a cutoff score
and Wimmer et al. (2000) the 20th percentile. The use of
a more lenient cutoff score may have resulted in children
being identified as having a double deficit in the absence
of noticeable reading problems.
Schatschneider et al. (2002) raised additional concerns about the use of arbitrary cutoff scores, particularly
with respect to the double-deficit group. They demonstrated that, because phonological awareness and RAN
were correlated with each other, children in the doubledeficit group could have a lower level of phonological
awareness than do children in the single-phonologicaldeficit group and have slower RAN than do children in
the single-naming-deficit group. In this case, it would be
difficult to determine whether the poorer performance of
the double-deficit group was due to having two deficits
or to having more severe deficits.
Compton, DeFries, and Olson (2001) conducted a
cross-sectional study examining the additive negative
effect of naming-speed and phonological deficits in
children with dyslexia. In a series of analyses, the
authors found a number of statistical problems associated with creating discrete groups based on continuous
variables. Compton et al. nicely demonstrated that categorizing children into subtypes based on arbitrary cutoffs
of continuous variables that are correlated resulted in
groups that differed in their level of phonological awareness. Importantly, when the groups were matched on
phonological awareness and RAN (i.e., the doubledeficit group and the RAN-deficit group were matched
on RAN, and the double-deficit and the phonological
deficit group were matched on phonological awareness),
many of the differences in reading disappeared.
530 Journal of Learning Disabilities
In contrast to Compton et al.’s (2001) findings, Kirby et al.
(2003) found evidence in support of the double-deficit
hypothesis in a longitudinal study extending from kindergarten to Grade 5. Kirby and his colleagues secured
that there was a reasonable degree of separation between
the groups by addressing Schatschneider and his colleagues’ (2002) concerns. The three groups, along with a
no-deficit group, were compared on word identification,
word attack, and passage comprehension. The participants in the no-deficit group performed consistently
well, and the participants in the double-deficit group
performed consistently poorly. Participants with single
phonological deficits performed poorly at the beginning
but then approached the no-deficit group in performance.
The participants in the naming-speed-deficit group did
poorly throughout, almost as poorly as the double-deficit
participants. Kirby et al. concluded that the double-deficit
group lagged behind the no-deficit group by almost 2 years
of achievement and were showing no sign of beginning to
accelerate or of catching up.
A critical consideration regarding the validity of doubledeficit subtyping has also been introduced by studies on
languages like German, Dutch, Italian, and Spanish,
which have a consistent orthography. In these languages,
grapheme-phoneme correspondence is rather consistent,
and as a result, the main difficulty for children with dyslexia is not decoding accuracy but reading speed (e.g.,
Landerl, 1997; van Daal & van der Leij, 1999; Wimmer,
1993; Wimmer, Landerl, & Frith, 1999; Zoccolotti et al.,
2005). In line with the results of studies on dyslexia in
orthographically consistent languages, Wimmer et al.
(2000) found that all three deficit groups showed close to
ceiling accuracy for text and word reading, and even nonword reading accuracy was around 90%. For reading rate,
there was a clearer picture of differences. The phonological deficit group exhibited a reliable reading rate deficit
for text only and showed no rate deficit at all for nonword
reading. In contrast, both the naming deficit and the
double-deficit groups exhibited reading rate impairments
for text, words, and nonwords and differed significantly
from both the no-deficit and the phonological deficit
group. However, even within the family of consistent
orthographies, there are conflicting findings concerning
the double-deficit hypothesis. For example, whereas
Wimmer and his colleagues (2000) reported that children
in the double-deficit group did not have any problems
reading nonwords accurately, Escribano (2007), in a
study with Spanish children with dyslexia, found that the
double-deficit group and the phonological deficit group
differed from the no-deficit group in pseudoword reading
accuracy. No significant differences were detected
between the phonological deficit and the double-deficit
groups. Nevertheless, Escribano’s findings should be
viewed with some caution, as group sizes were rather
small and the power of detecting significant differences
questionable.
To summarize, mixed findings have been reported for
the double-deficit hypothesis. Several researchers have
shown that children with deficits in both phonological
awareness and RAN experienced the most severe reading difficulties compared to children with single or no
deficits. However, other researchers have shown that
significant differences in the performance of the doubledeficit group may be the result of a statistical artifact and
of the language in which the children were tested.
Overview of the Present Study
The purpose of this study was to examine the doubledeficit hypothesis longitudinally from kindergarten to
Grade 2 in an orthographically consistent language (i.e.,
Greek). To our knowledge, this is the first study examining
the double-deficit hypothesis in Greek, but importantly, it
is one of the few longitudinal studies on this important
research topic (Kirby et al., 2003; Wimmer et al., 2000).
The study aimed to address the following questions:
1. Is a naming-speed deficit an independent core feature
of reading difficulties or an associated feature of a phonological deficit in Greek? And, therefore, do phonological awareness and RAN have an additive, negative
effect on reading, above and beyond that of a single
deficit? We expected that the double-deficit group
would have the lowest scores on all the measures of
reading and spelling.
2. Do the phonological awareness and naming-speed deficits occur early before reading develops or later when
reading fluency and orthographic processing become
important?
3. Are reading problems in orthographically consistent
languages primarily manifested as difficulties in orthographic processing and reading speed and not as problems in word- or pseudoword-reading accuracy? We
expected that the single- and the double-deficit groups
would perform equally well on reading accuracy measures due to the transparency of the Greek language and
that their difficulties would be on reading speed and
orthographic knowledge measures.
4. Finally, what is the independent and additive contribution of phonological ability and rapid naming as predictors of reading and orthographic skills concurrently and
longitudinally?
Papadopoulos et al. / Double-Deficit Hypothesis in Greek 531 Method
Participants
The original group of this large-scale study consisted
of 289 children in Cyprus coming from three different
districts and 42 urban and rural schools that are typical
in Cyprus, randomly chosen among those that traditionally collaborate with the University of Cyprus for
research and training purposes. The children were native
Greek speakers with no reported history of speech, language, or hearing difficulties. From this sample, four
groups were formed (a double-deficit group, two singledeficit groups, and a no-deficit group), on the basis of a
stepwise group selection process, to test the doubledeficit hypothesis.
Step 1 for group selection. The initial step for group
selection involved the selection of the criterion variables.
In an attempt to include as many as possible criteria compared to those used in previous research, we first examined the correlations between 10 phonological and 4
naming tasks (see next section for a description) with two
composite scores of fluency and with real and pseudoword
accuracy reading measures in Grade 1. Five phonological
(Rhyme Oddity, which taps phonological sensitivity at the
syllabic level, and Phoneme Elision, Sound Isolation,
Blending, and Initial Sound Oddity, which tap phonological sensitivity at the phonemic level) and two naming
tasks (RAN-Letters and RAN-Digits), all of which yielded
significant moderate to high correlations (rs > .40) with
the two composite scores for reading fluency and accuracy, were used as criterion variables to form the participating deficit groups. It is important to note that we chose
to define the groups using the Grade 1 scores because the
vast majority of the tasks yielded higher reliabilities in
Grade 1 than in kindergarten. In addition, the distribution
of phonological ability measures showed mild departures
from normality but no obvious outliers in Grade 1, and
participants’ ability to perform correctly the RAN-Letters
and RAN-Digits tasks that were used eventually as criterion measures for RAN was more accurate. Research has
consistently sho­wed that RAN-Letters and RAN-Digits
predict reading performance better than RAN-Colors and
RAN-Pictures do (e.g., Bowey et al., 2005; Wolf, Bally, &
Morris, 1986). This approach secured a reasonable degree
of separation between the groups and resulted in significant and robust group main effects.
Step 2 for group selection. Next, to differentiate the
four groups of children based on their phonological and
naming-speed scores in Grade 1, we selected for the deficit
groups the participants with performance falling below the
20th percentile on the composite scores of the criterion
variables (i.e., the five phonological measures and the two
rapid-naming measures). All the other participants scoring
above the 20th percentile on the composite scores of the
criterion variables were assigned to the control group. The
strict cutoff criterion of the 20th percentile was used deliberately, considering that our deficit groups derived from
population-based unselected samples. Our aim was to
minimize any risks for identifying children as having a
single or double deficit in the absence of noticeable reading problems, as has been observed in previous research
(e.g., Bowers et al., 1999; Manis et al., 2000; Sunseth &
Bowers, 2002).
Step 3 for group selection. To ensure that phonological
or naming-speed deficits are not confounded with intelligence deficits or demographic variables, this
final step for group selection involved the matching
of groups on verbal (Similarities and Vocabulary, Wechsler
Intelligence Scale for Children–Third Edition, Revised,
Wechsler, 1992; Greek adaptation by Georgas,
Paraskevopoulos, Bezevegis, & Giannitsas, 1997) and
nonverbal (Matrices, Das-Naglieri Cognitive Assess­ment
System, Naglieri & Das, 1997; Greek adaptation by
Papadopoulos, Georgiou, Kendeou, & Spanoudis, 2007)
ability measures. This was achieved after excluding from
the sample those participants who scored lower than the
15th percentile and higher than the 85th percentile on
these measures, namely, on Similarities, Vocabulary, and
Matrices, Wilks’s Λ, F(3, 238) = 1.17, p > .05 (Cohen’s d
for control vs. deficit groups ranged from .33 to .37, which
is a small effect). This selection resulted in a new grand
total of 242 children (117 girls and 125 boys). These new
groups were equivalent on age, F(3, 238) = 0.87, p > .05;
gender, χ2 = 3.13, p > .05; and parental education, χ2 =
5.64, p > .05. The parents of the participating groups had
predominantly low levels of education: less than a quarter
of the sample had parents who were college or university
graduates (14.5%), 26.9% of the parents had some college
education, and 58.6% had less than high school or were
high school graduates. The groups were as follows: (a) a
double-deficit group (DD; n =17, 9 girls and 8 boys), (b)
a phonological deficit group (PD; n = 33, 20 girls and 13
boys); (c) a naming deficit group (ND; n = 33, 17 girls and
16 boys); and (d) a control group exhibiting no deficits
(CnD; n = 159; 71 girls and 88 boys). The mean age of this
final set of children in the initial assessment (kindergarten)
was 5 years 8 months (SD = 0.31 years, minimum = 5.2,
maximum = 6.4), in the second assessment (in Grade 1), 6
532 Journal of Learning Disabilities
Table 1
Data on the Demographic and Ability Variables for the Double-Deficit Hypothesis, Phonological
Deficit, Naming Deficit, and Control–No Deficit Groups in Grade 1
Variable
Double
Deficit (n = 17)
Phonological
Deficit (n = 33)
Naming
Deficit (n = 33)
Control–No
Deficit (n = 159)
Age
Mean (SD)
6.62
(0.31)
6.56
(0.31)
6.57
(0.30)
6.64
Range
1.25
1.09
0.91
1.09
Gender
Girls
9
52.9%
20
60.6%
17
51.5%
71
Boys
8
47.1%
13
39.4%
16
48.5%
88
Parental education level
Less than high school
6
35.3%
8
24.2%
12
36.4%
45
High school graduate
7
41.2%
12
36.4%
9
27.3%
43
Some college
2
11.7%
9
27.3%
9
27.3%
45
College graduate
2
11.7%
4
12.1%
3
9.1%
26
Nonverbal ability
Cognitive Assessment System Matrices
8.29
(2.51)
8.33
(2.86)
8.12
(3.13)
9.22
Verbal ability
Similarities
4.35
(4.12)
4.36
(3.15)
4.82
(3.27)
4.85
Vocabulary
7.88
(4.70)
7.30
(3.77)
8.06
(3.84)
8.40
(0.28)
44.7%
55.3%
28.3%
27.0%
28.3%
16.4%
(2.47)
(3.31)
(4.05)
Note: The reported ability scores are raw scores, with standard deviations in parenthesis.
years 6 months (SD = 0.29 years, minimum = 6.1, maximum = 7.2), and in the final assessment (in Grade 2) 7
years 5 months (SD = 0.30 years, minimum = 7.0, maximum = 8.1). Table 1 shows the group scores on nonverbal
and verbal ability measures (raw scores are presented)
along with the mean and range of ages, gender distributions, and parental education level for all four groups in
Grade 1.
Measures
Selection Criteria
Phonological Sensitivity
Participants’ phonological skills were assessed using
10 tasks that differed in linguistic complexity with words
that were familiar to the participants. Six of these tasks
measured phonological ability at the syllabic level: Rhyme
Oddity, Rhyme Generation, Syllable Segmentation,
Syllable Completion, Final Syllable Oddity, and Initial
Syllable Oddity. The remaining 4 tasks tapped phonological ability at the phonemic level: Initial Sound Oddity,
Sound Isolation, Phoneme Elision, and Phoneme Blending.
The Rhyme Generation and Final Cluster Oddity tasks
consisted of 10 testing items. All other tasks were made
up of 15 testing items. This set of phonological tasks
has undergone extensive development and validation,
yielding high internal consistency (Papadopoulos,
Kendeou, & Spanoudis, 2009; Papadopoulos, Spanoudis,
& Kendeou, 2009). Specifically, Papadopoulos, Kendeou,
and Spanoudis have reported Cronbach’s alpha reliability values ranging from .77 to .94 for Rhyme Generation
and Syllable Completion, respectively, in kindergarten;
alpha values of .73 to .93 for Final Syllable Oddity and
Phoneme Elision, respectively, in Grade 1; and alpha
values of .72 to .93 for Final Syllable Oddity and Syllable
Segmentation, respectively, in Grade 2. Testing preparation, for all 10 tasks, included two sample items with
feedback regarding the correctness of the participant’s
answers to ensure that all participants knew what was
expected of them. All tasks were discontinued after four
failures. In all instances, a participant’s score was the
total number of correct responses.
Rhyme Oddity. This task was adapted to Greek by
Papadopoulos (2001) based on the work by Bradley and
Bryant (1985). The child was required to listen to three
words presented orally and to identify the one that ended
with a different rhyme compared to the other two (e.g.,
µπάλα/άλογο/γάλα; /bala/aloɣo/ɣala/; ball, horse, milk).
Rhyme Generation. In this task, the children were
asked to produce words that rhymed with a target word
(e.g., καλάθι → αγκάθι; /kalaθi/ → /aŋɡaθI/; basket →
thorn). Both real words and pseudowords were considered
Papadopoulos et al. / Double-Deficit Hypothesis in Greek 533 as permissible responses. The maximum time allowed to
generate a word for each target word was 30 seconds.
Syllable Segmentation. In this task, participants were
explicitly directed to tap the number of syllables in the
spoken words, aiming at revealing participants’ intuitive notions of syllabic units. The task was adapted from
Mann and Liberman (1984) and included words that varied in length and that contained one to six syllables. The
first two testing items had a simple structure: consonantvowel-consonant (CVC) or vowel-consonant-vowel
(VCV; πως; /pos/; how; and έλα; /εla/; come). All the
other words were made up of syllables with relatively
higher complexity, as defined by the number of consonants preceding a vowel or the use of diphthongs (example of a bisyllabic word: µπoύκλα; /bukla/; curl).
Syllable Completion. In this task, the participants
were asked to say aloud the second part of a bisyllabic
word, following the experimenter who pronounced the
first syllable. All words contained open syllables as target syllables, ending with a vowel, of CV (e.g., γά-τα; /
ɣa-ta/; cat), CCV (e.g., κά-δρο; /ka-ðro/; frame), or
CCCV (e.g., δέ-ντρο; /ðɛ-dro/; tree), structure. A set of
pictures, each depicting the matching familiar object,
was used.
Final Syllable Oddity. This task measured children’s
awareness of final syllable. The children were given triads
of bi- and trisyllabic spoken words and were asked to
select from the triad the “odd” word that ended differently
or did not alliterate with the other two. The words in each
triad had the same stress (marked with a diacritic in
Greek), a critical feature for the identity of the words in
stress-free languages such as Greek (Protopapas &
Gerakaki, in press). Given that Greek has predominantly
an open-syllable structure, the alliteration was based on
the initial consonant of the target cluster. The items were
split into three groups: those that ended with a CV (e.g.,
γάlα/γάτα/µπότα; /ɣala/ɣata/bota/; milk, cat, boot), CCV
(e.g., καρέκλα/κούκλα/πέπλα; /karɛkla/kukla/pɛpla/;
chair, doll, veils), and CCCV (e.g., κάστρα/δέντρα/
µάντρα; /kastra/ðɛdra/madra/; castles, trees, yard) syllable with the initial consonant being the only sound that
was different in the odd-out word in all instances.
Initial Syllable Oddity. In this task, participants were
asked to pay attention to initial syllables and select the
member of each three-item set that began with a different
syllable than the other two. This task was also adapted
from Bradley and Bryant (1985). There were three different groups of items: those that began with CV (e.g.,
μαμά/μέρα/μένω; /mama/mɛra/mɛno/; mom, day, stay),
CCV (e.g., κρατώ/κρεμώ/κρασί; /krato/krɛmo/krasi/;
hold, hang, wine), and CCCV (e.g., στρατός/στρέμμα/
στράτα; /stratos/strɛma/strata/; army, plot, street). With
the exception of only three item sets, which were used to
introduce the participants to the task, the odd-out word
was contrasted to the other two on the basis of the syllable’s vowel.
Initial Sound Oddity. In this task, the child had to indicate which word of a series of three words started with a
different sound (e.g., λάµπα/λίρα/ψωµί; /laba/lira/
psomi/; lamp, pound, bread). This kind of task has been
widely used to assess children’s phonemic awareness
(e.g., Byrne & Fielding-Barnsley, 1989, 1990; de Jong,
Seveke, & van Veen, 2000). The items used in this task
consisted primarily of bisyllabic and high-frequency
words that are typically acquired by Grade 1 children.
The first testing item was relatively easy, as only the oddout word started with a consonant. Half of the remaining
items were made up of words that could be contrasted on
the basis of the initial phoneme with relative easiness, as
none of them shared the same vowel in the first syllable.
The other half were somewhat more difficult, as the target word shared the same vowel with one of the other
two words (e.g., µέλι/µωρό/θέλει; /mεli/moro/θεli/;
honey, baby, wants).
Sound Isolation. This task was a Greek adaptation
(Papadopoulos, 2001) of the work of Wagner, Torgesen,
Laughon, Simmons, and Rashotte (1993) where they
compared alternative models of young readers’ phonological processing abilities. In this test, children were
asked to repeat the first, last, or middle sound in a word
(e.g., “Which is the middle sound in the word θέα; /θɛa/;
view). Testing items consisted of three- and four- phoneme, one- and two-syllable words.
Phoneme Elision. This task was also an adaptation of
the work by Wagner et al. (1993). In this task, children
were asked to repeat a word after deleting an identified
phoneme. The targeted phonemes were either vowels or
consonants, and their positions varied across items. After
deleting the target phoneme, the remaining phonemes
formed a word (e.g., Say the word τώρα; [/tora/; now],
after deleting the sound /t/ → ώρα; [/ora/; time]).
Blending. This task was designed to assess phonemeblending skills. Audio prompts presented the sounds of
two- to six-sound words separately, and the child was asked
to orally blend them into a word. The child’s response was
recorded as correct when she or he reproduced all the
534 Journal of Learning Disabilities
sounds in the final word. Word complexity was progressively more difficult. The first four words consisted of
two- to four-phoneme segments that were of CV or CVC
structure (e.g., ϕως; /fos/; light). The more difficult
items contained more complex phoneme segments, such
as CCV (e.g., στόµα; /stoma/; mouth). The component
sounds of each word were spoken at a 500-millisecond
interval.
Rapid Automatized Naming
This set of tasks was originally developed and used by
Papadopoulos, Charalambous, Kanari, and Loizou (2004).
All four measures were made up of two tasks (one
relatively easy and one more difficult) also made up of
20 testing items (five different stimuli, each repeated four
times). The items in each task were presented on a single
page, with four lines of 5 items per page. Order of items
changed from one line to the other. This format of the
RAN tasks differs from the type of tasks that are traditionally used in the literature in both number of items included
and, therefore, length of the task. In turn, this may explain
the somewhat low reliabilities reported below. Again, as
in the case of the phonological tasks, testing preparation
included a short sample. In all instances, the participant’s
score was the ratio between the number of items named
correctly divided by the time taken, for each pair of tasks.
RAN-Digits and RAN-Letters were used in all analyses
performed in Grades 1 and 2 (following the analysis on
criterion measures). RAN-Colors and RAN-Pictures
instead were used in kindergarten, given that a large number of participants could not perform properly the RANDigits and RAN-Letters tasks at that age.
RAN-Colors. Five basic and relatively more frequent
colors, namely, red, green, yellow, blue, and white were
included in the first task. In contrast, the second task was
composed of less frequent and secondary colors such as
pink, light blue, brown, orange, and purple. The participants had to say the names of the colors for an answer to
be recorded as correct. In the present sample, the correlations between successive grades were .55 from kindergarten to Grade 1 and .52 from Grade 1 to Grade 2.
RAN-Pictures. This measure was modeled after
Wimmer et al. (2000). The words of the first task started
with the same single-consonant cluster (καπέλο/
καρέκλο/κεράσι/καρότο/κλειδί; /kɑpɛlo/kɑrɛklɑ/
kerɑsɪ/karoto/kliðɪ/; hat, chair, cherry, carrot, key),
whereas the words of the second task started with different consonant clusters (ϕράουλα/πλυντήριο/σκύλος/
σταυρός/µπανάνα; /fraʊla/plintirio/skilos/staʌros/
banana/; strawberry, washer, dog, cross, banana). In the
present sample, the correlations between successive grades
were .55 from kindergarten to Grade 1 and .51 from
Grade 1 to Grade 2.
RAN-Digits. The digits from 1 to 5 were included in
the first task. The second task was comprised of the digits
6 to 9 and 0 (zero). The participants had to say the name
of the digit for an answer to be recorded as correct. In the
present sample, the correlation between Grade 1 and
Grade 2 performance was .61.
RAN-Letters. The letters of the first task were only
vowels (α, η, ε, ο, υ), and the letters of the second task
were only consonants that share similar characteristics
and are usually confused by poor readers in Greek (π, τ,
σ, δ, θ). The participants had to say the name of the letter,
and not the sound that it makes, for an answer to be
recorded as correct. In the present sample, the correlation
between Grade 1 and Grade 2 performance was .56.
Reading
Word reading. Two standardized measures were used
to assess participants’ word-reading ability, namely, a
real-word-reading task and a pseudoword-reading task
(Papadopoulos & Spanoudis, 2007; Cronbach’s alpha for
the real-word-reading task was .97 in Grade 1 and .81 in
Grade 2, respectively, and for the pseudoword-reading
task .92 in Grade 1 and .69 in Grade 2, respectively). In
both tasks, the instruction to the participants was to read
the entire list of words. Both accuracy score, that is, the
total number of words read correctly, and reading speed
(fluency) score, that is, the number of words read correctly within 60 seconds, were recorded for each participant. We used both scores for at least two reasons: It has
been already shown in previous studies in Greek
(Papadopoulos, 2001; Porpodas, 1999) that children with
reading difficulties achieve a very high accuracy rate
(almost 98% for real-word reading and 92% for pseudoword reading), despite the difficulty of the words.
Similar findings are reported from cross-language reading studies (Seymour, Aro, & Erskine, 2003). This means
that in reading a regular writing system like Greek, even
beginning readers with reading difficulties manage to
decode almost any letter array successfully. However,
(a) this cognitive processing deteriorates when a time
frame is set and the child is required to read as many
words as possible within it, and (b) research to date in
orthographically consistent languages has not reached
agreement about whether children’s difficulties are
solely observed in reading speed (e.g., Wimmer et al.,
Papadopoulos et al. / Double-Deficit Hypothesis in Greek 535 1999); Wimmer et al., 2000) or in decoding accuracy as
well (Escribano, 2007). By examining group differences
in both accuracy (i.e., words read correctly in the whole
list) and fluency (i.e., words read correctly in 60 seconds) measures, we were able to answer the essential
question about the nature of the deficits observed in a
language with a transparent orthography. Both the realword and the nonword lists were preceded by a practice
list to familiarize children with the list-reading procedure and with nonwords, respectively.
Word Identification. This test consisted of 85 words
forming a 2 × 2 × 2 factorial design in terms of frequency
(high/low), orthographic regularity (regular/exception),
and length (bisyllable/trisyllable). Half of the words
were sampled from the first-grade language books,
and the other half taken from second-grade language
books, following Porpodas (1999) and used initially by
Papadopoulos (2001). The stimulus words were mainly
nouns, with a few adjectives and verbs.
Word Attack. This task consisted of 45 pronounceable
nonwords that were derived from real words after changing two or three letters (either by substituting them or
using them backward). The task started with bisyllabic
words and ended with five-syllable words.
Reading Comprehension
Two tasks were administered to the participants to
assess reading comprehension skills. Passage Compre­
hension was administered in both Grades 1 and 2, whereas
the Maze task was administered only in Grade 2. These
tasks were piloted in Greek for the purpose of the study,
in the absence of standardized measures.
Passage Comprehension. This test was an adaptation
of the Woodcock Reading Mastery Tests–Revised
(WRMT-R; Woodcock, 1987). The participant was
required to read a short passage (usually two to three
lines long) and identify a keyword (represented by a
blank line) missing from the passage. To successfully
complete the item, a participant generally had to understand not only the sentence containing the missing word
but also the remaining sentence (or sentences). Before
starting the test, the examiner instructed the child to read
each passage silently and then orally provide a suitable
word for the blank space. A sample item was administered to ensure that the participant understood what was
expected. The version used in this study contained 68 items.
The participant’s total score was the number of correctly
filled blanks. The task was discontinued after four consecutive mistakes. Cronbach’s alpha reliability coefficient
in our sample was .88 in Grade 1 and .92 in Grade 2.
Maze. The Maze Test of Curriculum Based Measure­
ment (Deno, 1985; Espin & Foegen, 1996) is a test of
reading comprehension developed for students with
reading and learning disabilities. The test requires students to read passages that include incomplete sentences.
The reader is asked to choose the correct word from
three options (one correct and two incorrect) to appropriately complete the sentence as he or she reads the text.
Three written passages are presented one at a time to
students, using a booklet. These passages are similar to
texts that the individuals may be exposed to in their own
reading or in school, with the exception that they have
these multiple-choice test sentences embedded within
them. Students have 1 minute to read as much of each
passage as possible and, while reading, circle the appropriate word to accurately complete the target sentences.
This same pattern is repeated for all three passages.
Students are guided through two practice sentences and
then continue with the remainder of the test. The total
time for test administration ranges from 5 to 10 minutes.
Students’ scores consist of the average number of correct
words chosen minus the number of incorrect words chosen. Test-retest reliability scores could not be calculated
for this sample. However, in a different same-age cohort,
the correlation between Grade 2 and Grade 3 performance was .55 (Kendeou & Papadopoulos, 2009).
Orthographic Processing
Orthographic Choice. This task was adapted from the
work of Olson and colleagues (e.g., Olson, Forsberg,
Wise, & Rack, 1994; Olson, Wise, Conners, Rack, &
Fulker, 1989) and was initially used by Papadopoulos,
Kendeou, and Spanoudis (2009). It consisted of 20 items
that were constructed in a way that phonological transcription alone did not reliably result in identifying the
one orthographically correct word among the three
words included in each item (e.g., αρέσει/αρέσι/αρέσοι;
/aresi/; like). Participants had to use their knowledge of
the orthographic patterns for the given words in order to
identify the one that was both phonologically and orthographically correct. The resulting score was the number
of orthographically correct spellings identified by the
child. Cronbach’s alpha reliability coefficient in our
sample was .56 in Grade 1 and .77 in Grade 2. Although
the reliability observed in Grade 1 could be considered as
somewhat low, it is important to note that the distribution
536 Journal of Learning Disabilities
of scores was normal, with values of kurtosis and skewness being within acceptable ranges.
Word Chains. In this task, the children were asked to
scan words presented as a continuous line of print without interword spaces (e.g., boygomeet). The children
were given 1 minute and were asked to identify the
words in each row by drawing a line to indicate where
the spaces should be (e.g., boy/go/meet). The test
included a total of 15 rows of words of increasing length.
The first 2 rows consisted of two words put together,
whereas the last 3 items consisted of seven words put
together. The individual’s score on this task was the
number of correctly placed slashes. Cronbach’s alpha
reliability coefficient in our sample was .72 in Grade 1
and .83 in Grade 2.
Procedure
In all three assessments, participants were tested individually in sessions lasting approximately 60 minutes,
between February and April each year. All testing took
place during school hours in a private room in the participants’ respective schools. Experimenters were trained
graduate research assistants enrolled in educational psychology courses, blind to grouping of children. The presentation of the tasks was counterbalanced across the
participants in all years, to control for any effects of task
complexity on the performance. None of the participants
in the deficit groups received systematic intervention in
their respective schools over the course of the study.
With regard to classroom instruction, in kindergarten
the children attended a program that included mostly
social activities and games with semiformal cognitive or
linguistic training. In relation to language and literacy
development specifically, children became aware of the
range of books and tapes or CDs available to them while
teachers enhanced the opportunities for learning and of
pleasure from reading books on the children’s part. The
development of listening skills was also of major importance while the children were read stories. Children were
also constantly introduced to new vocabulary while they
were trying to record what they had learned or found out.
Drawing and prewriting activities were also included on
a daily basis. Finally, rhyming and odd-out word activities for which the children had to identify the word that
differed from two or three others in its first or ending
syllable (or sound) were occasionally practiced. Generally,
the aims concentrated on aiding children to learn to be
more aware of print around them and to enjoy participating in routine literacy activities.
In Grade 1, the children received formal reading and
spelling instruction in a basal reading series that
emphasized primarily word recognition, reading comprehension, and incidentally, word-decoding and lettersound correspondences through syllable-splitting
activities. Phonological processing skills, in turn, were
fostered through segmentation and blending activities
as the key strategies.
Similarly, the Grade 2 curriculum expanded on the
knowledge acquired in Grade 1, focusing particularly on
reading and spelling words with less common spelling
patterns and multisyllabic words. The children also
learned prepositions and prepositional phrases. Gen­
erally, grammar and syntax activities such as identifying
pronouns, learning and using standard punctuation, recognizing compound sentences, and writing friendly letters were some of activities introduced in the daily
program. Students also continued to work on their oral
reading fluency.
Results
Comparison of Single, Double-Deficit,
and Control Groups
In Grade 1, three MANOVA analyses (see Note 1)
were performed, with group as a fixed factor and phonological, RAN, reading, and orthographic measures as the
dependent variables. The main group effects were significant for phonological (4 Groups × 5 Tasks), Wilks’s
Λ = .325, F(5, 234) = 21.68, p < .001; RAN (4 Groups ×
2 Tasks), Wilks’s Λ = .519, F(2, 237) = 30.61, p < .001;
and reading and orthographic measures (4 Groups × 7
Tasks), Wilks’s Λ = .585, F(7, 232) = 6.52, p < .001.
Subsequent univariate analyses demonstrated that the
main effect of group was significant for all measures
(Table 2). In turn, post hoc tests using Bonferroni adjustment for multiple comparisons, tested with Type I error
set at .05, one-sided (see Note 2), showed that the cutoffs
described in the selection procedure resulted in groups
that were significantly different on the phonological and
RAN measures. The DD and PD groups performed significantly lower than the ND and control groups in all
phonological tasks (p < .001). In turn, the DD and ND
groups performed significantly lower than the PD and
control groups with regard to RAN-Digits and RANLetters (p < .001). The PD group did not differ from the
CnD group on the RAN measures, and conversely, the ND
group was not different from the CnD group on the phonological measures. In addition, the DD group did not
Papadopoulos et al. / Double-Deficit Hypothesis in Greek 537 Table 2
Descriptive Statistics and F Values for the Double-Deficit Hypothesis, Phonological Deficit,
Naming Deficit, and Control–No Deficit Groups on Phonological, Rapid-Automatized-Naming
(RAN), Reading, and Orthographic Measures in Grade 1
Double Deficit
(n = 17)
Phonological
Deficit (n = 33)
Naming Deficit
(n = 33)
Variable
M
M
M
(SD)
(SD)
(SD)
Control–No Deficit
(n = 159)
M
(SD)
Phonological
Rhyme Oddity
3.12c,d
(3.25)
2.76c,d
(3.32)
8.94
(3.73)
10.18
(3.80)
Initial Sound Oddity
2.47c,d
(2.67)
1.67c,d
(2.26)
7.91
(4.12)
8.72
(4.46)
Sound Isolation
7.59c,d
(4.91)
6.18c,d
(4.82)
13.09
(2.07)
13.60
(1.74)
Phoneme Elision
1.47c,d
(1.91)
1.36c,d
(2.49)
9.03
(3.57)
10.22
(3.85)
Blending
2.18c,d
(1.47)
2.30c,d
(2.14)
9.52
(3.24)
9.84
(3.36)
RAN
Digits-Ratio
0.97b,d
(0.20)
1.47c
(0.19)
1.08d
(0.15)
1.50
(0.30)
Letters-Ratio
0.91b,d
(0.17)
1.33c
(0.23)
0.88d
(0.20)
1.40
(0.26)
Word reading
WID Speed
9.65b,c,d
(6.04)
17.34d
(4.35)
16.73d
(6.57)
23.46
(8.15)
WAT Speed
7.94c,d
(5.52)
10.70d
(3.85)
12.33d
(6.14)
16.19
(5.03)
WID Accuracy 32.71b,c,d
(23.50)
53.77d
(22.51)
56.42d
(18.66)
67.66
(13.60)
WAT Accuracy
18.47b,c,d
(12.28)
26.21d
(11.18)
29.18d
(9.60)
33.22
(7.23)
Orthographic Orthographic Choice
7.35d
(1.97)
6.09c,d
(3.79)
8.30
(2.49)
8.89
(2.14)
Word Chains
2.47c,d
(1.62)
2.58c,d
(2.74)
4.21
(2.39)
4.74
(2.86)
Reading comprehension
Passage Comprehension
12.47d
(7.38)
13.09d
(7.71)
15.45
(6.17)
17.07
(7.33)
F Value
42.31***
35.58***
86.06***
78.63***
77.39***
38.30***
58.22***
25.41***
23.30***
27.80***
19.31***
12.78***
8.29***
4.34**
Note: Subscript letters indicate that group means differ significantly between each other; group comparisons are marked from left to right only:
d = control–no deficit group; c = naming deficit group; b = phonological deficit group. WID = Word Identification; WAT = Word Attack.
**p < .01. ***p < .001.
differ from the PD group on the phonological measures
and from the ND group on the RAN measures.
The main objective of the group comparisons on word
reading, orthographic processing, and reading comprehension was to determine whether the DD group is more
impaired than the single-deficit and the CnD groups
(Question 1). The answer to this question was affirmative. The DD group performed significantly lower than
the single-deficit and control groups on all word-reading
measures except pseudoword fluency (in which case the
DD group did not differ from the PD group), with the vast
majority of the p values at < .001 level. On the other
hand, the PD and ND groups exhibited a reliable reading
rate and accuracy deficit when compared to the CnD
group (with the vast majority of p values at < .001).
However, the pattern of results for orthographic spelling
and reading comprehension was different. The DD and
PD groups’ performance was significantly different from
that of the ND and CnD groups in almost all comparisons
of orthographic processing measures, with the PD group
exhibiting robust differences in both tasks (for Word
Chains, PD < ND, p < .05, and DD < ND, p < .05; for
Orthographic Choice, PD < ND, p < .001, but DD = ND;
in turn, for Word Chains, PD < CnD, p < .001, and DD <
CnD, p < .001; for Orthographic Choice, PD < CnD, p <
.001, and DD < CnD, p < .05). This means that the PD
group was both markedly impaired in identifying the
orthographically correct word among three similar phonological transcriptions and in recognizing fast and accurately the words in Word Chains. The DD group, in turn,
performed equally well with the ND group on the phonetic spelling accuracy task (Orthographic Choice), albeit
differently from the CnD group. No significant differences, however, were observed between the ND and the
CnD groups on these measures. With respect to reading
comprehension, the CnD group outperformed the DD
(p < .01) and PD (p < .01) groups, but not the ND group
on the Reading Comprehension task. In sum, in Grade 1,
the deficit groups, on the basis of the double-deficit
hypothesis, differed mainly with respect to word-reading
rate and accuracy and partly to orthographic processing
and reading comprehension measures.
After having selected the groups in Grade 1, we tested,
in retrospect, their performance on the phonological and
538 Journal of Learning Disabilities
RAN tasks in kindergarten. Similarly, we examined
group differences in all the dependent measures a year
later, in Grade 2. In kindergarten, in the case of the RAN
tasks, groups were compared only in naming pictures
and colors because very few children had managed to
complete successfully the letter- and digit-naming tasks.
In kindergarten, the results from the MANOVA analyses replicated the effects in Grade 1, with both phonological, Wilks’s Λ = .889, F(5, 234) = 1.87, p < .05, and
RAN measures, Wilks’s Λ = .907, F(2, 237) = 3.96, p <
.001 (Table 3). Subsequent univariate analyses indicated
that the groups differed only in two out of the five phonological tasks, namely, Rhyming Oddity, F(3, 238) = 2.82,
p < .05, η2 = .034, and Sound Isolation, F(3, 238) = 4.65,
p < .01, η2 = .055. Similarly, the main effect of group was
significant for both RAN measures: RAN-Pictures, F(3,
238) = 6.21, p < .001, η2 = .073, and RAN-Colors, F(3,
238) = 5.80, p < .001, η2 = .068. Post hoc tests revealed
that no significant group differences were observed
among the three deficit groups in any of the phonological
measures. Also, results showed that the CnD group outperformed all three deficit groups on Sound Isolation
(p < .05) and RAN-Colors (p <. 05, for DD and PD
groups, and p < .001 for the ND group). There were also
significant differences between the DD and CnD groups
on Rhyming Oddity (p < .05) and Initial Sound Oddity
(p < .05). In contrast, no group differences were observed
in the case of Phoneme Elision and Blending between
the deficit and control groups, a result suggesting that
these tasks were too difficult for the participants in kindergarten. Finally, the ND and DD groups were significantly more impaired in RAN-Pictures than the PD group
(p < .05), whose performance was similar to that of the
CnD group. This was the only reliable difference, consistent also with the selection procedure based in Grade 1
group performances. Thus, as far as the second question
of the study is concerned, the answer is that although
phonological awareness and naming-speed deficits may
occur early, before reading develops, the three deficit
groups are not easily distinguished from each other, particularly in terms of phonological impairments.
In Grade 2, the main group effects were significant in
all five MANOVA analyses performed with phonological, Wilks’s Λ = .830, F(5, 234) = 3.01, p < .001, η2 =
.060; RAN, Wilks’s Λ = .868, F(2, 237) = 5.54, p < .001,
η2 = .068; word-reading, Wilks’s Λ = .803, F(4, 235) =
4.34, p < .001, η2 = .070; orthographic processing,
Wilks’s Λ = .898, F(2, 237) = 4.20, p < .001, η2 = .052; and
reading comprehension, Wilks’s Λ = .898, F(2, 237) =
4.15, p < .001, η2 = .053, measures (Table 4). Subsequent
univariate analyses demonstrated that the main effect of
group was significant for all the measures except for the
real-word-reading accuracy and the Orthographic Choice
tasks.
Post hoc group comparisons showed that the DD group
kept performing significantly lower than the CnD group
on all measures and lower than the PD and ND groups in
the vast majority of the phonological, RAN, and wordreading measures. The single-deficit groups in turn
appeared to improve to the extent that they did not differ
from each other in any of the criterion (phonological and
rapid naming) or dependent measures (word reading,
orthographic processing, and reading comprehension),
albeit their performance was markedly different from
that of the CnD group on the criterion and some of the
dependent measures.
On the one hand, with respect to the performance of
the DD group, this was significantly different from the
single-deficit groups on the most demanding phonological tasks, namely, Sound Isolation (at p < .01 and p <
.001, for ND and PD group comparisons, respectively),
Phoneme Elision (p < .01), and Blending (p < .05).
Similarly, the DD group was reliably slower on the RAN
tasks than the PD group (p < .05 for RAN-Digits and p <
.001 for RAN-Letters) and slower than the ND group on
the RAN-Letters (p < .05) only. As far as reading is concerned, the DD group read real words slower than both
single-deficit groups (p < .001 and p < .05, for PD and
ND, respectively) and pseudowords slower than the PD
group (p < .01). The same performance was observed in
the case of the Maze Comprehension task (DD = ND <
PD, p < .05), also a speeded task.
On the other hand, it is of importance that the majority
of the differences that were observed between the singledeficit and control groups on the reading and orthographic processing measures in Grade 1 were not
observed in Grade 2. The PD group read slower than the
CnD group only in the case of word attack (p < .05), a
task requiring efficient use of phonological skills during
decoding (Papadopoulos, 2001; Porpodas, 1999). In
turn, although the ND group appeared to improve accuracy for word reading, this was not also observed in the
case of reading fluency, where the CnD group outperformed the ND group (p < .001). Interestingly enough,
this reading rate impairment was also revealed in the
case of the Maze task (also a speed-related task; p < .01).
Finally, the PD group performed worse than the CnD
group on the Word Chains task (p < .001), and the ND
group was significantly poorer than the CnD group on
the Passage Comprehension task (p < .05).
In sum, the findings in Grade 2 were different from
those in Grade 1. The single deficit in phonological
abilities had a limited, negative effect on reading fluency
and orthographic processing (only in the Word Chains
Papadopoulos et al. / Double-Deficit Hypothesis in Greek 539 Table 3
Descriptive Statistics and F Values for the Double-Deficit Hypothesis, Phonological Deficit,
Naming Deficit, and Control–No Deficit Groups on Phonological and Rapid-Automatized-Naming
(RAN) Measures in Kindergarten
Double Deficit
(n = 17)
Phonological
Deficit (n = 33)
Naming Deficit
(n = 33)
Variables
M
M
M
(SD)
(SD)
(SD)
Control–No
Deficit (n = 159)
M
(SD)
Phonological
Rhyme Oddity
4.18d
(4.45)
5.30
(4.72)
5.27
(4.46)
6.83
(4.79)
Initial Sound Oddity
2.65d
(3.41)
3.42
(3.36)
4.09
(3.03)
4.60
(3.44)
Sound Isolation
1.35d
(3.50)
2.67d
(3.89)
2.42d
(3.09)d
4.26
(4.32)
Phoneme Elision
0.88
(1.69)
1.45
(2.84)
1.09
(1.86)
1.75
(3.47)
Blending
0.41
(1.00)
0.70
(1.65)
1.61
(2.62)
1.72
(3.04)
RAN
Pictures-Ratio
0.52b,d
(0.17)
0.62c
(0.16)
0.53d
(0.16)d
0.64
(0.16)
Colors-Ratio
0.48d
(0.26)
0.53d
(0.18)
0.48d
(0.14)d
0.61
(0.21)
F Values
2.82*
2.52
4.65**
0.72
2.20
6.21***
5.80***
Note: Subscript letters indicate that group means differ significantly between each other; group comparisons are marked from left to right only:
d = control–no deficit group; c = naming deficit group; b = phonological deficit group.
*p < .05. **p < .01. ***p < .001.
Table 4
Descriptive Statistics and F Values for Double-Deficit Hypothesis, Phonological Deficit,
Naming Deficit, and Control–No Deficit Groups on Phonological, Rapid-Automatized-Naming
(RAN), Reading, and Orthographic Measures in Grade 2
Double Deficit
(n = 17)
Phonological
Deficit (n = 33)
Naming Deficit
(n = 33)
Control No
Deficit (n = 159)
Variable
M
M
M
M
(SD)
(SD)
(SD)
(SD)
Phonological
Rhyme Oddity
8.47d
(4.36)
9.76d
(4.90)
10.73
(3.96)
11.78
(3.73)
Initial Sound Oddity
7.94d
(4.74)
7.79d
(5.00)
9.24
(5.19)
10.95
(4.35)
Sound Isolation
10.06b,c,d
(4.87)
12.45d
(3.74)
13.03
(3.57)
13.67
(2.65)
Phoneme Elision
8.18b,c,d
(3.99)
11.27d
(4.04)
11.76
(4.15)
12.78
(3.00)
Blending
6.35b,c,d
(3.86)
9.33d
(3.84)
9.48
(3.74)
10.75
(3.65)
RAN
Digits-Ratio
1.46b,d
(0.58)
1.78
(0.50)
1.67d
(0.31)
1.87
(0.42)
Letters-Ratio
0.39b,c,d
(0.27)
0.83
(0.41)
0.66d
(0.26)
0.81
(0.37)
Word Reading
WID Speed
30.65b,c,d
(10.52)
41.41
(11.67)
38.03d
(8.50)
44.78
(10.26)
WAT Speed
19.06b,d
(6.23)
23.87d
(6.04)
21.84d
(5.84)
26.28
(5.76)
WID Accuracy 71.59c,d
(8.50)
73.22
(8.44)
76.32
(3.95)
75.57
(7.39)
WAT Accuracy
31.47d
(9.89)
33.87
(5.72)
34.03
(6.90)
36.04
(5.52)
Orthographic Orthographic Choice
11.59
(2.50)
12.65
(1.54)
11.66
(2.41)
12.38
(2.32)
Word Chains
9.65d
(2.98)
9.81d
(4.65)
11.34
(3.27)
12.78
(4.47)
Reading Comprehension
Passage Comprehension
20.87d
(5.59)
24.52
(6.60)
23.11d
(6.52)
26.06
(5.74)
Maze
0.89b,d
(1.21)
2.38
(1.98)
1.75d
(1.61)
2.86
(1.80)
F Values
5.36***
6.24***
7.53***
10.45***
8.23***
5.77***
8.23***
12.17***
11.71***
2.53
3.93**
1.63
6.36***
4.97**
7.95***
Note: Subscript letters indicate that group means differ significantly between each other; group comparisons are marked from left to right only:
d = control–no deficit group; c = naming deficit group; b = phonological deficit group. WID = Word Identification; WAT = Word Attack.
**p < .01. ***p < .001.
540 Journal of Learning Disabilities
task) a year later and no effect on reading accuracy. The
single deficit in naming speed, in turn, appeared to have
basically a negative effect on reading measures requiring a
speeded response. There was also a moderate impairment
of the single-naming-deficit group for passage comprehension. Probably the most consistent finding was that
the performance of the DD group was generally lower
than that of the other groups.
Taken together with the results in Grade 1, the answer
to the third question of the study, regarding the manifestation of reading problems in orthographically consistent
languages, is clear. The DD group performed worse than
the single-deficit and control groups on reading accuracy
and fluency and worse than the ND group on orthographic processing in Grade 1, group effects that weakened a year later in Grade 2. In turn, although the
single-deficit groups exhibited impairments on reading
accuracy and orthographic processing in the first place,
they appeared to find ways to compensate for these difficulties in relation to the control group across time.
Regression Analyses
To answer the fourth question of the study, namely,
what is the independent and additive contribution of phonological ability and RAN as predictors of reading and
orthographic skills concurrently and longitudinally, we
conducted a set of hierarchical regression analyses on the
full sample (n = 242). To perform these analyses, we first
computed composite scores expressed in z score units for
each one of the predictors (phonological awareness and
RAN) and dependent measures (reading fluency, reading
accuracy, orthographic processing, and reading comprehension; in the latter, WRMT-R and Maze formed a standardized composite score in Grade 2). This calculation
was possible given the high correlations among the different measures. Specifically, the RAN measures correlated significantly with each other (rs ranged from .40 to
.59) for Grade 1 and 2, respectively. Similarly, the correlations among the five phonological tasks were strong,
with r values ranging from .50 between Rhyme Oddity
and Sound Isolation to .75 between Phoneme Elision
and Blending in Grade 1, and from .47 between Initial
Sound Oddity and Sound Isolation to .69 between Initial
Sound Oddity and Phoneme Elision, in Grade 2. In contrast, the correlations among the RAN and phonological
measures were remarkably low (with r values < .30) with
many of those being nonsignificant.
Similarly, with respect to the dependent variables, the
word fluency measures correlated highly, with r values at
.76 and .69, for Grade 1 and 2, respectively. The respective correlations between the word accuracy measures
were .76 and .46, and the correlations between the orthographic processing measures were .33 and .37. Finally,
the two reading comprehension measures correlated significantly (r = .41) in Grade 2.
With regard to the regression analyses, we examined
separately the unique and common contribution of phonological ability and RAN as follows: in the first set of
models we entered phonological ability and RAN as
single predictors of reading and orthographic processing
skills. This was followed by a set of models also examining the unique contribution of phonological ability and
RAN (entered successively in Block 2) as predictors of
reading and orthographic skills. Finally, we examined
the common contribution of phonological ability and
RAN on the dependent measures. These sets of models
tested concurrently, in Grades 1 and 2, and longitudinally, from Grade 1 to Grade 2, the predictive validity of
phonological ability and RAN on the criterion measures.
The results are summarized in Table 5.
These analyses showed that phonological ability and
naming speed accounted for unique variance in almost
all reading and orthographic processing measures in both
concurrent and longitudinal analyses. The only exceptions to this were Orthographic Choice and reading comprehension in Grade 1, where naming speed accounted
for small and nonsignificant amounts of variance. In
both instances, phonological ability uniquely predicted a
significant amount of variance independent of RAN
(24% for orthographic processing and 9% for reading
comprehension). In addition, phonological ability
appeared to uniquely predict a higher amount of total
variance independent of RAN in the vast majority of the
analyses. The independent contribution of RAN was
higher than the contribution of phonological ability only
in the case of word-reading fluency (in the concurrent
and longitudinal analyses in Grade 2) and reading comprehension in Grade 2. The highest portion of common
variance of these two predictors was observed in the
concurrent analysis with word-reading fluency tasks
in Grade 1, accounting for 10% (38% – 17% – 11%) of
the total variance, and in Grade 2, accounting for 11%
(33% – 6% – 16%) of the total variance.
Discussion
In this study, we tested the double-deficit hypothesis
in Greek by employing a rigorous methodological design
to define the double-deficit, single-deficit, and control
groups. We predicted that the double-deficit hypothesis
would be extended to the Greek language, with the children belonging to the DD group showing pronounced
541
.164***
–
.01
.059*** .12***
–
.176***
.065***
–
.02*
.041*** .04***
–
.084***
PA
RAN
PA + RAN
PA
RAN
PA + RAN
RAN
.216***
–
.06***
.131*** .14***
–
.273***
PA
PA
RAN
PA + RAN
R 2
PA
RAN
.117***
–
.16***
.225*** .05***
–
.273***
.174***
–
.16***
.271*** .06***
–
.334***
.276***
–
.11***
.214*** .17***
–
.382***
R2
Unique
Contribution
Word Reading Fluency
PA
RAN
.083***
–
.04**
.070*** .05***
–
.120***
.099***
–
.04**
.081*** .05***
–
.135***
.250***
–
.00
.012
.24***
–
.251***
R 2
Unique
Contribution
Orthographic Processing
PA
.00
–
RAN
.050***
–
.091*** .02*
.113***
.06***
–
.180***
–
.07***
.154*** .10*** –
.251***
.094***
–
.006
.09***
.094***
R2
Unique
Contribution
Reading Comprehensiona
a. In the concurrent Grade 1 analyses, the Woodcock Reading Mastery Tests–Revised (WRMT-R) was used as the dependent measure of reading comprehension; in all other analyses,
a composite score of the WRMT-R and Maze was used instead.
*p < .05. **p < .01. ***p < .001.
Grade 1 (concurrently)
1
2
3
Grade 2 (concurrently)
1
2
3
Grade 1 to Grade 2 (longitudinally)
1
2
3
Variable
Unique
Contribution
Model
Word Reading Accuracy
Table 5
Regression Results Predicting Reading Subskills in Grade 1 and Grade 2 (concurrently) and in Grade 2 From Grade 1
(longitudinally), Phonological Ability (PA) and Rapid-Automatized-Naming (RAN) Composite Scores
542 Journal of Learning Disabilities
deficits in reading and orthographic processing tasks,
compared to either one of the single-deficit groups or to
the CnD group, in the first years of schooling. The
results confirmed our predictions and were consistent
with the findings of previous studies demonstrating that
children with a double deficit have both a naming-speed
and a phonological deficit when engaged in wordreading, text-reading, and orthographic processing tasks
(e.g., Wimmer et al., 2000; Wolf & Bowers, 1999).
In relation to the first question of the study, the results
confirmed our expectation that the DD group would
exhibit greater dysfunction in reading and orthographic
processing compared to the single-deficit and CnD
groups. It was also interesting to observe that although
the three deficit groups were not differentiated in the vast
majority of the tasks in kindergarten (with the exception
of RAN-Colors, where DD = ND < PD = CnD groups),
the between-group differences were maximized in Grade
1 (when formal reading instruction was taking place) and
were retained in Grade 2. This overall finding regarding
the lower reading and orthographic processing performance of children experiencing both phonological
awareness and naming-speed deficits is consistent with
that of previous research (e.g., Escribano, 2007; Jiménez
et al., 2008; Kirby et al., 2003; Manis et al., 2000; Wolf
& Bowers, 1999).
Regarding the question about how the reading problems manifest themselves in Greek, contrary to previous
findings in languages with transparent (e.g., Wimmer
et al., 2000) and opaque orthographies (e.g., Manis et al.,
2000), the single-deficit groups performed significantly
lower than the CnD group on all word-reading accuracy
and fluency measures in Grade 1. Specifically, with
respect to the performance of the ND group, deficits were
also observed in both word- and text-reading levels in the
speeded measures. This is probably one of the reasons
that some of these children with a single-naming-speed
deficit may not be identified by their teachers as poor
readers until Grade 3 or later, when fluency problems
interfere seriously with reading comprehension (Wolf &
Katzir-Cohen, 2001). The association between naming
speed and reading comprehension has been suggested by
Kirby et al. (2003) and has also been replicated in the
study by Johnston and Kirby (2006) with poor readers in
Grades 4 and 5. At the very least, the predictive ability of
RAN to discriminate readers in terms of reading comprehension needs further validation.
In addition, contrary to the findings of previous studies in English (e.g., Bowers, Sunseth, & Golden, 1999;
Sunseth & Bowers, 2002), the ND group was better than
the DD and PD groups and comparable to the CnD group
on the two orthographic processing tasks in Grade 1,
indicating that, in our sample, the naming deficits were
not associated with low levels of orthographic processing skills. Similar findings have recently been reported
in Spanish (Jiménez et al., 2008). Certainly, these findings challenge Bowers and Wolf’s (1993) theoretical
account that if letter recognition is proceeding too
slowly—reflected in slow RAN performance—letter
representations in words will not be activated in sufficiently close temporal proximity to induce sensitivity
to commonly occurring orthographic patterns. Evidence
in support of this theoretical proposal would be if our
ND group was particularly impaired in orthographic
processing measures.
The discrepancy between our findings and those rep­
orted by Bowers and her colleagues could be attributed to
at least two reasons. First, the participants in studies conducted by Bowers and colleagues (Bowers et al., 1999;
Sunseth & Bowers, 2002) were older than the participants
in our study. This difference is important, as there is evidence showing that RAN is more strongly related to orthographic processing in later grades (Grade 3 and beyond)
than in earlier grades (Georgiou, Parrila, Kirby, &
Stephenson, 2008). Thus, it is legitimate to hypothesize
that if the same children were followed up in Grade 3, the
relationship between RAN and orthographic processing
could be stronger. Second, Bowers and Wolf’s (1993)
theoretical account refers to a different level of orthographic processing, namely, the sublexical level of orthographic processing. We measured orthographic processing
at the word-specific (lexical) level (see Hagiliassis, Pratt,
& Johnston, 2006, for a detailed description of the levels
of orthographic processing). Recently, Powell, Stainthorp,
and Stuart (2008) demonstrated that children with fast
RAN performance did not perform worse than children
with slow RAN performance on Orthographic Choice (a
measure of lexical orthographic processing) but performed
significantly poorer on Word Likeness (a measure of sublexical orthographic processing). Thus, had we also
administered a measure of sublexical orthographic processing, the relationship between RAN and orthography
could have been different.
With respect to the degree of impairment among children with a naming-speed deficit, our findings in Grade 1
are consistent with the work of Manis and his colleagues
(2000). The ND group was less impaired compared to
the PD group, most likely because formal reading instruction was under way. However, in Grade 2, the greatest
impairments in reading fluency and reading comprehension were associated with the ND group (Kirby et al.,
2003). This shift in the contribution of the linguistic and
cognitive skills underpinning reading development in
children who are relatively poor in reading is of major
Papadopoulos et al. / Double-Deficit Hypothesis in Greek 543 importance, as it indicates that the observed relationships
do not hold up the same way over time (Kendeou, van
den Broek, White, & Lynch, 2007, in press; Rapp, van
den Broek, McMaster, Kendeou, & Espin, 2007). It is,
therefore, essential to test these relationships longitudinally to obtain a full picture of the significance and
the role of these deficits over time. Vukovic and Siegel
(2006), in their review, reached the same conclusions,
suggesting that the majority of the research has accumulated little evidence from longitudinal studies and that
there is a remarkable need to depart from the cross-sectional designs to properly investigate the double-deficit
hypothesis. The present study attained this objective.
The single-phonological-deficit group showed mostly
deficient orthographic and poor decoding skills that were
also witnessed, albeit to a lesser extent, in Grade 2. The
orthographic processing deficits were serious enough to
differentiate the PD group from both the ND and CnD
groups in Grade 1, an effect that was only partially replicated in Grade 2 (only in Word Chains where PD <
CnD group; see Note 3). As for the remaining measures,
only the deficits in nonword fluency were observed
again in Grade 2, despite the fact that the PD group continued to perform lower than the CnD group in all five
phonological ability measures. This result was expected
on the basis of the importance of phonological processing in both orthographic processing skills and decoding skills (Manis et al., 2000; Share, 1995), particularly
in Greek, a language with a transparent orthography
(Georgiou et al., 2008; Papadopoulos & Georgiou, in
press). This finding cannot be attributed to home literacy
factors (Manolitsis, Georgiou, Stevenson, & Parrila, in
press). Overall, the PD group performed poorly at the
beginning but then approached the CnD group in performance more than the ND group did, which continued to
show deficits in word-reading fluency and passage comprehension, a finding that coincides with those of previous research (e.g., Kirby et al., 2003). This is probably
explained by the fact that RAN and not phonological
deficits were those that differentiated more reliably the
deficit groups from the CnD group in the first place.
Apparently, and before formal reading instruction begins,
problems in languages with more transparent orthographies are manifested as difficulties in naming speed and
not as problems in phonological ability.
The limited contributing role of phonological ability in
discriminating the four groups in kindergarten may be
attributed to the structure of phonological ability in learning to read Greek that is best conceptualized as a unitary
construct, developing in a continuous way with invariant
structure across time (Papadopoulos, Kendeou, &
Spanoudis, 2009; Papadopoulos, Spanoudis, & Kendeou,
2009). This means that there is a considerable overlap
among the various phonological skills, which, in fact,
may not allow individual differences to be easily detected
before the child starts learning to read. Only when reading begins do the dimensions of linguistic complexity or
the types of the cognitive operations required to perform
the various phonological tasks appear to adequately
reflect individual differences in unified, higher order phonological ability (Anthony, Lonigan, Driscoll, Phillips, &
Burgess, 2003; Papadopoulos, Kendeou, & Spanoudis,
2009). Consequently, it is likely that phonological deficits
in kindergarten are masked by the fact that children learning Greek manipulate both syllabic and phonemic grainsize units equally the same at this age because of the
advantage of the consistent orthography. This means that
children learning Greek do not rely heavily on specific
word units (rhyme, syllable, or phoneme) to successfully
perform a given task at the age of 5, but they may use the
phonological representations of any grain-size unit that
are available to them. This interpretation appears also to
be supported by the coefficients of the phonological ability measures that become stronger from Grade 1 onward.
This likely reflects the beneficial effects of reading
instruction on phonological awareness that are more evident in orthographically transparent languages (Goswami,
Ziegler, & Richardson, 2005; Holopainen, Ahonen,
Tolvanen, & Lyytinen, 2000).
In sum, although the phonological and naming-speed
impairments are independent core features of reading difficulties in young Greek readers, the impairments in phonological ability are not as robust as those in RAN at the
age of 5, between the deficit and the control groups, due
to the transparency of the language. In turn, it is not a
surprise that the most significant differences in those skills
between the deficit groups and the CnD group were
observed in Grade 1, when reading accuracy, fluency, and
orthographic processing became important. Taken together,
our results suggest that due to the regular structure of the
Greek language, naming deficits are more persistent than
phonological deficits among children experiencing reading difficulties in early years. The latter group gradually
found means to compensate for poor reading performance.
By Grade 2, the PD group managed to read better than the
ND group that kept struggling with speed in reading at
both the word and text levels, despite the fact that both
single-deficit groups improved to the extent they did not
differ from each other on the selection measures (naming
speed and phonological ability).
The results from the regression analyses further extend
the above findings. Specifically, it was shown that both
544 Journal of Learning Disabilities
phonological ability and naming speed accounted for
unique variance but, importantly, in different outcome
measures. RAN accounted for more unique variance in
word- and text-fluency measures. Phonological skills, in
turn, accounted for more unique variance in Orthographic
Choice (in Grade 1) and word-reading accuracy (in
Grade 2). These results converge with those of previous
studies suggesting that the predictive power of RAN on
reading accuracy is lower than that of phonological ability in languages with transparent orthography (Georgiou,
Parrila, & Papadopoulos, 2008; Papadopoulos, Georgiou,
Parrila, & Anastasiou, 2005). In addition, the pattern of
differences in the amount of unique variance associated
with either phonological ability and naming speed is
consistent with the double-deficit hypothesis.
Overall, the findings of the present study clearly demonstrate the presence of pronounced deficits in phonological ability and naming speed among Greek children
identified as exhibiting reading difficulties. These findings raise an interesting question, namely, whether the
double-deficit hypothesis is supported in the context of
children who have a formal diagnosis of dyslexia.
Previous studies have shown that the possibility for the
predictions of the double-deficit hypothesis to be confirmed is higher with children identified with dyslexia
than with children from a field population (e.g., Katzir,
Kim, Wolf, Morris, & Lovett, 2008; Lovett et al., 2000).
In either case, however, it is important to study longitudinally the time course of the effects of naming speed
and phonological skills to make any direct inference
about their role in dyslexia.
Indeed, our results point to this need, as it was shown
that the contribution of naming speed and phonological
skills to the definition of poor reading in Greek is different at different points of development. The deficits
appear to be primarily circumscribed in the processes of
RAN. A year later, when reading is formally taught, phonological skills become the most powerful predictor,
whereas RAN becomes more powerful in Grade 2. Also,
children with a naming-speed deficit make slower progress in reading development although their reading performance is similar to—if not better than—that of the PD
group in Grade 1. This change in the importance of the
predictors at different points of assessment challenges
both the nature of the constructs measured and the durability of their effects over time (see also Kirby et al.,
2003; Spector, 2000). This interpretation appears to be in
line both with Georgiou et al.’s (2008) proposal that
RAN measures different processing skills at different
points in time and with the stability indexes of RAN in
the current study—albeit not very strong, for they are not
weak either, which suggests that there are some changes
in the relative standing of the participants on RAN from
year to year. Probably, further research that would investigate the cognitive processes that drive the relationship
between RAN and reading or the role of RAN in different reading and orthographic tasks across time may help
to clarify the issue of stability indexes of RAN more
systematically.
What this study, therefore, offers to the ongoing discussion about these specific deficits of children with
reading difficulties is that it provides the impetus of further research to either verify or falsify the double-deficit
hypothesis with individuals learning to read in orthographically transparent languages. At least, with regard
to the pattern of difficulties observed in affected individuals, the precise nature and the contribution of the
predictors change over time. This suggests, in turn, that
the coexistence of naming-speed and phonological
awareness deficits in children learning to read in a transparent orthography merits further attention.
Notes
1. Rather than one-way MANOVAs, 2 × 2 MANOVA analyses
with the groups merged as high and low in phonological ability spell
out and rapid automatized naming (RAN) was carried out at each
grade level to confirm the sample selection. The results of the two
analyses were consistent, confirming the group selection on the basis
of the criterion variables: Most main effects of RAN and phonological ability were significant, whereas the interactions were not. Also,
it appeared that phonological impairments have their greatest impact
in Grade 1 and their effect weakened in Grade 2, whereas the reverse
was true for RAN impairments: They appeared to have their greatest
impact in Grade 2. We have chosen to report the one-way MANOVAs
because they provide more detail as to how the four groups differ
systematically across measures and grades.
2. In the absence of any empirical findings showing that the
double-deficit group would perform better than any single-deficit
group or that the single-deficit groups would perform better than the
control group, we tested the null hypotheses with a one-sided, rather
than two-sided, alpha level.
3. Although we used this task to measure lexical orthographic
processing, it is possible that the children applied phonological recoding strategies to identify the boundaries of words, and that is why the
phonological deficit group was impaired on this task.
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Timothy C. Papadopoulos, PhD, is an assistant professor of
educational psychology at the University of Cyprus. His current research focuses on the cognitive and linguistic skills
underpinning reading development, reading difficulties and
different subtypes of reading disability, and the cognitive
remediation for the enhancement of reading skills.
George K. Georgiou, PhD, is an assistant professor in the
Department of Educational Psychology at the University of
Alberta, Edmonton, Canada. He is interested in cross-linguistic
predictors of reading and in particular the effects of rapid naming on reading accuracy and fluency.
Panayiota Kendeou, PhD, is an assistant professor of educational psychology at McGill University, Montreal, Canada.
Her current research focuses on the cognitive processes
that support memory and learning in the context of reading
comprehension.
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