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Projeto de investigação
Mechanisms of Implicit Learning: From Artificial Grammars to Dyslexia
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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.
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.
Object Naming in Dyslexic Children: More Than a Phonological Deficit
Publication . Araújo, Susana; Faísca, Luís; Bramão, Inês; Inácio, Filomena; Petersson, Karl Magnus; Reis, Alexandra
In the present study, the authors investigate how some visual factors related
to early stages of visual-object naming modulate naming performance in dyslexia. The
performance of dyslexic children was compared with 2 control groups—normal readers
matched for age and normal readers matched for reading level—while performing a discrete
naming task in which color and dimensionality of the visually presented objects were
manipulated. The results showed that 2-dimensional naming performance improved for
color representations in control readers but not in dyslexics. In contrast to control readers,
dyslexics were also insensitive to the stimulus’s dimensionality. These findings are unlikely
to be explained by a phonological processing problem related to phonological access or
retrieval but suggest that dyslexics have a lower capacity for coding and decoding visual
surface features of 2-dimensional representations or problems with the integration of visual
information stored in long-term memory.
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.
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Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
Concurso para Projectos de I&D em todos os Domínios Científicos - 2009
Número da atribuição
PTDC/PSI-PCO/110734/2009