Can’t See the Words for the Letters: Whole Word Processing in Adolescents and a Novel “Visual” Intervention for Dyslexia

Abstract

Individuals with developmental dyslexia, considered as a group, perform poorly on tasks that involve phonological analysis, such as applying sight-sound rules to read new words, or analysing words into their component sounds (De Groot, Huettig, & Olivers, 2016; Temple & Marshall, 1983). However, dyslexia is also associated with other types of difficulties. For example, in some individuals, reading latencies increase disproportionately with the length of the word (De Luca, Barca, Burani, & Zoccolotti, 2008; Spinelli et al., 2005) suggesting they may have difficulties recognising familiar words as whole units (“whole word” processing).

This thesis examined the relationship between the word length effect and overall reading proficiency in a diverse sample of 49 adolescents. We found that the length effect was a unique predictor of reading proficiency, even after factoring out variance in phonological skills (measured using a nonword reading task). We also tested the recent hypothesis that visual attention span - the number of letters a reader can capture in a single glance - is important for efficient whole word reading (Bosse, Tainturier, & Valdois, 2007). Contrary to this hypothesis, we found no association between the word length effect and scores on a standard measure of visual attention span (a partial report task).

We also explored whether reading-delayed adolescents could benefit from an intervention targeting their specific cognitive profile. Five cases demonstrating a selective difficulty with either “phonological” or “whole word” skills completed two interventions. One targeted phonological skills: participants were trained to recognise and apply common sight-sound correspondences. The other targeted whole word skills: we reasoned that training participants to recognise commonly-occurring letter redundancies (e.g. ogue: rogue, synagogue, dialogue) could reduce the load on parallel letter processing. Only one of the five cases showed greater improvement in (untrained) word reading accuracy following their “target” intervention. However, four of the five showed intervention-specific improvements in reading latency. These results suggest that it could be valuable to consider heterogeneity when treating reading delay.