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Projeto de investigação
ESTUDO DOS PROCESSOS COGNITIVOS SUBJACENTES À PERTURBAÇÃO DE LEITURA E PERTURBAÇÃO DE NOMEAÇÃO VISUAL NA POPULAÇÃO DISLÉXICA
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Lexical and Phonological Processes in Dyslexic Readers: Evidence from a Visual Lexical Decision Task
Publication . Araújo, Susana; Faísca, Luís; Bramão, Inês; Petersson, Karl Magnus; Reis, Alexandra
The aim of the present study was to investigate whether reading failure in the context of an
orthography of intermediate consistency is linked to inefficient use of the lexical orthographic reading procedure. The performance of typically developing and dyslexic
Portuguese-speaking children was examined in a lexical decision task, where the stimulus
lexicality, word frequency and length were manipulated. Both lexicality and length effects
were larger in the dyslexic group than in controls, although the interaction between group
and frequency disappeared when the data were transformed to control for general
performance factors. Children with dyslexia were influenced in lexical decision making by
the stimulus length of words and pseudowords, whereas age-matched controls were
influenced by the length of pseudowords only. These findings suggest that non-impaired
readers rely mainly on lexical orthographic information, but children with dyslexia
preferentially use the phonological decoding procedure—albeit poorly—most likely because
they struggle to process orthographic inputs as a whole such as controls do. Accordingly,
dyslexic children showed significantly poorer performance than controls for all types of
stimuli, including words that could be considered over-learned, such as high-frequency
words. This suggests that their orthographic lexical entries are less established in the
orthographic lexicon.
What does rapid naming tell us about dyslexia?
Publication . Araújo, Susana; Faísca, Luís; Petersson, Karl Magnus; Reis, Alexandra
This article summarizes some of the important findings from research evaluating the relationship between
poor rapid naming and impaired reading performance.
Substantial evidence shows that dyslexic readers have
problems with rapid naming of visual items. Early research assumed that this was a consequence of phonological processing deficits, but recent findings suggest
that non-phonological processes may lie at the root of
the association between slow naming speed and poor
reading. The hypothesis that rapid naming reflects an
independent core deficit in dyslexia is supported by the
main findings: (1) some dyslexics are characterized by
rapid naming difficulties but intact phonological skills;
(2) evidence for an independent association between
rapid naming and reading competence in the dyslexic
readers, when the effect of phonological skills was controlled; (3) rapid naming and phonological processing
measures are not reliably correlated. Recent research
also reveals greater predictive power of rapid naming, in particular the inter-item pause time, for high-frequency
word reading compared to pseudoword reading in developmental dyslexia. Altogether, the results are more
consistent with the view that a phonological component
alone cannot account for the rapid naming performance
in dyslexia. Rather, rapid naming problems may emerge
from the inefficiencies in visual-orthographic processing
as well as in phonological processing.
Visual rapid naming and phonological abilities: Different subtypes in dyslexic children
Publication . Araújo, Susana; Pacheco, Andreia; Faísca, Luís; Petersson, Karl Magnus; Reis, Alexandra
One implication of the double-deficit hypothesis for dyslexia is that there should be subtypes of dyslexic
readers that exhibit rapid naming deficits with or without concomitant phonological processing problems.
In the current study, we investigated the validity of this hypothesis for Portuguese orthography, which is more
consistent than English orthography, by exploring different cognitive profiles in a sample of dyslexic children.
In particular, we were interested in identifying readers characterized by a pure rapid automatized naming deficit.
We also examined whether rapid naming and phonological awareness independently account for individual
differences in reading performance. We characterized the performance of dyslexic readers and a control group of
normal readers matched for age on reading, visual rapid naming and phonological processing tasks. Our results
suggest that there is a subgroup of dyslexic readers with intact phonological processing capacity (in terms of both
accuracy and speed measures) but poor rapid naming skills. We also provide evidence for an independent
association between rapid naming and reading competence in the dyslexic sample, when the effect of
phonological skills was controlled. Altogether, the results are more consistent with the view that rapid naming
problems in dyslexia represent a second core deficit rather than an exclusive phonological explanation for the
rapid naming deficits. Furthermore, additional non-phonological processes, which subserve rapid naming
performance, contribute independently to reading development.
Component Processes Subserving Rapid Automatized Naming in Dyslexic and Non-dyslexic Readers
Publication . Araújo, Susana; Inácio, Filomena; Francisco, Ana; Faísca, Luís; Petersson, Karl Magnus; Reis, Alexandra
The current study investigated which time components of rapid automatized naming (RAN)
predict group differences between dyslexic and non‐dyslexic readers (matched for age and
reading level), and how these components relate to different reading measures. Subjects performed two RAN tasks (letters and objects), and data were analyzed through a response
time analysis. Our results demonstrated that impaired RAN performance in dyslexic readers
mainly stem from enhanced inter‐item pause times and not from difficulties at the level of
post‐access motor production (expressed as articulation rates). Moreover, inter‐item pause
times account for a significant proportion of variance in reading ability in addition to the effect of phonological awareness in the dyslexic group. This suggests that non‐phonological factors may lie at the root of the association between RAN inter‐item pauses and reading
ability. In normal readers, RAN performance was associated with reading ability only at early
ages (i.e. in the reading‐matched controls), and again it was the RAN inter‐item pause times
that explain the association.
Electrophysiological correlates of impaired reading in dyslexic pre-adolescent children
Publication . Araújo, Susana; Bramão, Inês; Faísca, Luís; Petersson, Karl Magnus; Reis, Alexandra
In this study, event related potentials (ERPs) were used to investigate the extent to which dyslexics (aged
9–13 years) differ from normally reading controls in early ERPs, which reflect prelexical orthographic
processing, and in late ERPs, which reflect implicit phonological processing. The participants performed
an implicit reading task, which was manipulated in terms of letter-specific processing, orthographic
familiarity, and phonological structure. Comparing consonant- and symbol sequences, the results showed
significant differences in the P1 and N1 waveforms in the control but not in the dyslexic group. The
reduced P1 and N1 effects in pre-adolescent children with dyslexia suggest a lack of visual specialization
for letter-processing. The P1 and N1 components were not sensitive to the familiar vs. less familiar orthographic sequence contrast. The amplitude of the later N320 component was larger for phonologically
legal (pseudowords) compared to illegal (consonant sequences) items in both controls and dyslexics.
However, the topographic differences showed that the controls were more left-lateralized than the dyslexics. We suggest that the development of the mechanisms that support literacy skills in dyslexics is
both delayed and follows a non-normal developmental path. This contributes to the hemispheric differences observed and might reflect a compensatory mechanism in dyslexics.
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Entidade financiadora
Fundação para a Ciência e a Tecnologia
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Número da atribuição
SFRH/BD/28488/2006