Visual crowding effects in typical and dyslexic readers

?uniewska, M. 1 , Wójcik, M. 1, 2 & Jednoróg, K. 1

1 Laboratory of Language Neurobiology, Nencki Institute of Experimental Biology, Polish Academy of Sciences
2 University of Warsaw

We investigate the effects of visual crowding on reading in typically reading children and with developmental dyslexia. Previous research claimed that extra-large letter spacing boosts accuracy and reading speed in children with dyslexia on the fly (Zorzi et al., 2012).
Here we compare oral reading speed and accuracy, text comprehension and fixation duration in dyslexic (n = 39) and typical readers (n = 36) across three conditions: regular, extra-spaced and crowded sentences.
In general, children with dyslexia had lower reading rate, accuracy, and comprehension together with longer fixations than typical readers. Visual crowding influenced reading accuracy and fixation duration in both groups: the larger the inter-letter spaces, the lower the number of errors and the shorter the fixations. Additionally, crowding was greater in dyslexic than in typical readers for both reading accuracy and fixation duration as revealed by an interaction of group and condition. Crowding did not affect reading speed and text comprehension.
The effect of crowding is clearly visible in dyslexia, but it is not limited to children with reading impairment (similarly as in Hakvoort et al., 2017). However, the improvements seen in dyslexia are not as spectacular as in previous research (Zorzi et al., 2012).