Toward the characterization of a visual form of developmental dyslexia: Reduced visuo-attentional capacity for processing multiple stimuli made of separable features

ABSTRACT

Some dyslexics cannot process multiple letters simultaneously. It has been argued that this reduced visuo-attentional (VA) letter span could result from poor reading ability and experience. Here, moving away from reading context, we showed that dyslexic group exhibited slower visual search than normal readers group for “symbols”, defined as graphic stimuli made up of separable visual features, but not for filled objects. Slowness in symbol visual search was explained by reduced VA field and atypical ocular behaviour when processing those letter-like stimuli and was associated with reduced VA letter span and impaired elementary visuo-spatial perception. Such a basic visual search deficit can hardly be attributed to poor reading ability and experience. Moreover, because it is specific to letter-like stimuli (i.e., “symbols”), it can specifically hinder reading acquisition. Symbol visual search can easily be tested in the pre-reading phase, opening up prospects for early risk detection and prevention of VA dyslexia.

KEYWORDS:

• Feature-absent visual search
• spatial binding
• gaze-contingent moving window
• visual attention span
• feature integration

Acknowledgements

Thanks to all the families who gave their time to participate in this study. Thanks to Sonia Alouche for her valuable administrative support. This work was conducted in accordance to ethical comity CPP Ile de France VI decision 22/11/2017 69HCL17-0333.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by INSERM, CNRS, Pulsalys, Fondation de France and Mustela.