Examining the relationship between speechreading, audiovisual integration, and reading in adults with developmental dyslexia

Abstract

Developmental dyslexia is characterised by persistent difficulties with accurate and fluent reading and spelling. It is commonly associated with weaknesses in phonological processing and often co-occurs with conditions such as developmental language disorder (DLD) and attention deficit hyperactivity disorder (ADHD). Evidence from normal-hearing, deaf, and blind populations indicates that visual speech contributes to the development and refinement of phonological representations from early life. Visual articulatory cues can support speech intelligibility when auditory input is degraded and can influence auditory perception when visual and acoustic speech information conflict.

Research on visual and audiovisual speech processing in dyslexia remains limited and inconsistent. Some studies report poorer performance in visual-only or audiovisual conditions, whereas others find no significant group differences. This makes it difficult to determine whether atypical performance reflects impaired speechreading, broader differences in audiovisual processing, or task-specific factors such as noise. The present thesis therefore aimed to clarify the relationship between speechreading, audiovisual processing, phonological skills, and reading in adults with developmental dyslexia.

Across four studies, behavioural and electrophysiological (ERP) methods were used to compare adults with dyslexia and neurotypical readers. Speechreading was assessed under visual-only conditions, while non-speech and speech-based audiovisual tasks measured behavioural and neurophysiological responses. Overall, adults with dyslexia performed comparably to neurotypical readers on visual-only speechreading tasks, including tasks involving phonological and lexical-semantic knowledge. In contrast, group differences were more consistent in audiovisual tasks: adults with dyslexia showed attenuated neurophysiological responses in both non-speech and speech-based audiovisual oddball paradigms. Exploratory analyses further suggested that stronger speechreading and audiovisual speech-processing abilities were associated with stronger phonological skills within the dyslexia group.

Thesis is embargo until 31 Decmeber 2031.

Date of Award	Dec 2026
Original language	English
Awarding Institution	Queen's University Belfast
Sponsors	Republic of Türkiye Ministry of National Education
Supervisor	Tim Fosker (Supervisor), William Curran (Supervisor) & Fiona Kyle (Supervisor)