Crowding is defined as the negative effect obtained by adding visual distractors
around a central target which has to be identified. Some studies have suggested the
presence of a marked crowding effect in developmental dyslexia (e.g. Atkinson, 1991;
Spinelli et al., 2002).
Inspired by Spinelli’s (2002) experimental design, we explored the hypothesis
that the crowding effect may affect dyslexics’ response times (RTs) and accuracy in
identification tasks dealing with words, pseudowords, illegal non-words and symbolstrings.
Moreover, our study aimed to clarify the relationship between the crowding
phenomenon and the word-reading process, in an inter-language comparison
perspective. For this purpose we studied twenty-two French dyslexics and twenty-two
Italian dyslexics (total forty-four dyslexics), compared to forty-four subjects matched
for reading level (22 French and 22 Italians) and forty-four chronological age-matched
subjects (22 French and 22 Italians).
Children were all tested on reading and cognitive abilities. Results showed no
differences between French and Italian participants suggesting that performances were
homogenous. Dyslexic children were all significantly impaired in words and
pseudowords reading compared to their normal reading controls.
Regarding the identification task with which we assessed crowding effect, both
accuracy and RTs showed a lexicality effect which meant that the recognition of words
was more accurate and faster in words than pseudowords, non-words and symbolstrings.
Moreover, compared to normal readers, dyslexics’ RTs and accuracy were
impaired only for verbal materials but not for non-verbal material; these results are in
line with the phonological hypothesis (Griffiths & Snowling, 2002; Snowling, 2000;
2006) . RTs revealed a general crowding effect (RTs in the crowding condition were
slower than those recorded in the isolated condition) affecting all the subjects’
performances. This effect, however, emerged to be not specific for dyslexics. Data
didn’t reveal a significant effect of language, allowing the generalization of the
obtained results.
We also analyzed the performance of two subgroups of dyslexics, categorized
according to their reading abilities. The two subgroups produced different results
regarding the crowding effect and type of material, suggesting that it is meaningful to
take into account also the heterogeneity of the dyslexia disorder.
Finally, we also analyzed the relationship of the identification task with both
reading and cognitive abilities.
In conclusion, this study points out the importance of comparing visual tasks
performances of dyslexic participants with those of their reading level-matched
controls. This approach may improve our comprehension of the potential causal link
between crowding and reading (Goswami, 2003).
| Identifer | oai:union.ndltd.org:unibo.it/oai:amsdottorato.cib.unibo.it:1011 |
| Date | 28 April 2008 |
| Creators | Bellocchi, Stéphanie <1980> |
| Contributors | Contento, Silvana |
| Publisher | Alma Mater Studiorum - Università di Bologna |
| Source Sets | Università di Bologna |
| Language | Italian |
| Detected Language | English |
| Type | Doctoral Thesis, PeerReviewed |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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