Volume 4, Number 5, Article 4, Pages 388-402 doi:10.1167/4.5.4 http://journalofvision.org/4/5/4/ ISSN 1534-7362
Eye movement control during single-word reading in dyslexics
Manfred MacKeben
The Smith-Kettlewell Eye Research Institute, San Francisco, California, USA
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Susanne Trauzettel-Klosinski
Department of Pathophysiology of Vision and Neuro- ophthalmology, University Eye Hospital, Tübingen, Germany
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Jens Reinhard
Department of Pathophysiology of Vision and Neuro- ophthalmology, University Eye Hospital, Tübingen, Germany
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Ute Dürrwächter
Department of Child and Adolescent Psychiatry and Psychotherapy, University of Tübingen, Germany
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Martin Adler
Department of Pathophysiology of Vision and Neuro- ophthalmology, University Eye Hospital, Tübingen, Germany
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Gunther Klosinski
Department of Child and Adolescent Psychiatry and Psychotherapy, University of Tübingen, Germany
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Abstract

We investigated whether dyslexics make instantaneous automatic adjustments of reading saccades depending on word length. We used a single-word reading paradigm on 10 dyslexic and 12 normally reading children aged 11-15 years. Eye movements were recorded by scanning laser ophthalmoscope (SLO) while subjects read single words of different length aloud. All subjects passed standardized prescreening tests, which included a reading test, to exclude those with discernible deficits of eyesight, oculomotor skill, or intellectual development. We measured number, direction, frequency, and amplitude of saccades, as well as the durations of inter-saccadic intervals, as functions of word length. The results show that word length influences the number and amplitude of reading saccades in both subject groups, but this relationship showed quantitatively significant group-specific differences: Both groups showed a gradual increase of the saccade amplitudes in either direction dependent on word length, but the gain of this function was significantly lower in the dyslexics. The durations of holding phases between saccades were significantly longer in the dyslexics, and accordingly, we found a lower rate of occurrence of saccades per unit time in the dyslexics. Forward saccade amplitudes showed no correlation with the duration of the preceding or following holding phases in either group. The data show that the mechanisms enabling dyslexics to make instantaneous adjustments of reading saccades depending on word length are present but quantitatively impaired. This supports the view that these adjustments may help dyslexics to increase reading speed, but that they cannot utilize them to the same extent as normal readers.

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History
Received April 3, 2002; published May 14, 2004
Citation
MacKeben, M., Trauzettel-Klosinski, S., Reinhard, J., Dürrwächter, U., Adler, M., & Klosinski, G. (2004). Eye movement control during single-word reading in dyslexics. Journal of Vision, 4(5):4, 388-402, http://journalofvision.org/4/5/4/, doi:10.1167/4.5.4.
Keywords
dyslexia, perceptual span, saccades, inter-saccadic, language processing
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