Developmental surface dyslexias - Naama Friedmann

cortex 44 (2008) 1146–1160 1151
Table 2 – Percentage error in reading aloud of irregular and relatively regular words, and of words with and without
potentiophones
Participant
Irregular with
potentiophone
Irregular no
potentiophone
Relatively regular
with potentiophone
Total irregular or
potentiophone
Relatively regular
no potentiophone
SH 37 28 45 35 8
GL 39 31 47 38 8
OF 29 18 34 25 8
YR 56 48 56 52 11
TM 50 37 60 49 9
NT a 56 50 – 51 0
OM 37 29 39 35 3
BZ 21 10 46 23 0
AS 25 18 38 26 11
OS 44 37 56 44 3
AK 20 18 28 22 5
AM 23 31 45 33 11
AL 20 13 32 20 5
KR 21 21 31 24 3
NF 46 28 27 33 3
IR 11 7 23 14 6
YD 14 3 20 12 1
Control groups
Fifth grade 1.5 4.3 7.8 5.0 1.6
Middle school .9 2.2 3.8 2.5 .3
Adults 0 .3 2.2 1.0 .1
a NT was not tested on regular potentiophones.
each age group we found the cut-off point beyond which the
number of errors was already significantly larger ( p < .05)
than the number of errors in the control group.
2.3. Results
2.3.1. Reading aloud
The results of the reading aloud task, presented in Table 2,
clearly indicate that the participants had surface dyslexia.
They had significant difficulties in reading aloud of the target
irregular and potentiophonic words, whereas they read the
relatively regular words better. Each of the participants had
significantly more errors than their matched control group
(for the two adults, t(15) > 11, p < .001; for the four participants
in middle school, t(23) > 6, p < .0001; for the children in fifth
and sixth grade, t(27) > 3, p < .002).
Their reading errors were characteristic of surface dyslexia:
they produced errors of regularization, reading with
the incorrect vowel when the vowel was not represented,
reading with the incorrect mapping to sound of sound-ambiguous
letters, and incorrect stress position (see Appendix B for
error examples).
Participants’ reading of irregular and potentiophonic
words was significantly poorer than their reading of the relatively
regular words that did not have potentiophones,
z(16) ¼ 3.6, p ¼ .0003. 4 Importantly, whether or not a word
had a potentiophone had a crucial effect on reading. The participants
made more errors when the target irregular word
had a potentiophone than when it did not. Relatively regular
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.
words with potentiophones were read significantly poorer
than relatively regular words without potentiophones,
z(16) ¼ 3.5, p ¼ .0005, and irregular words were read significantly
poorer when they had a potentiophone than when
they did not, z(15) ¼ 3.06, p ¼ .002. This also held individually
for 14 of the participants. The older participants made the
fewest errors on the irregular words without potentiophone,
possibly because they learned to block or avoid nonlexical
responses. 5
The surface dyslexia of 15 of the participants was pure,
with very few errors that did not result from reading via
grapheme-to-phoneme conversion, as seen in Table 3. Notice
that none of the participants produced semantic or morphological
paralexias, indicating that they were not reading aloud
via the semantic system. TM and AK had developmental
attentional dyslexia in addition to developmental surface
dyslexia, but because the words were presented to them separately,
a single word at a time, this did not affect their performance
in the study. AK also had a mild letter position
dyslexia 6 (Friedmann and Gvion, 2001, 2005; Friedmann and
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 regularity
and frequency relations between 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 nine middle migrations
(14%) (both tests from the TILTAN test battery, Friedmann and
Gvion, 2003).