Effectiveness of adapted vowel-based literacy instruction in minimally verbal adolescents with autism and intellectual and developmental disability

Background: Literacy skills enhance communication for students who use or need augmentative and alternative communication (AAC); however, many are not targeted in literacy instruction due to low educational expectations and limited evidence-based practices. Purpose: This study examined the effectiveness of adapted Hebrew vowel-based literacy instruction for minimally verbal (MV) adolescents with autism and intellectual disabilities (ID), addressing a research gap in this population. Methods: Three MV adolescents with autism and ID (ages 11-16) participated in a multiple baseline design for adapted vowel instruction (module 1), following an AB design with two students for three sequential consonant-vowel (CV) modules. Each module spanned 6-8 sessions. Five vowels (a, e, i, o, u), five CV syllable combinations per consonant module (/m/, /sh/, /l/), and 10 related words were targeted, utilizing visual-spatial adaptations and nonverbal response options. Results: Evidence supported a functional relationship between adapted vowel instruction and students' vowel identification (TAU-U = 0.643, p < 0.001), with two participants showing significant gains and all three meeting the visual analysis criterion. Improvements were observed in CV syllables (/m/, /sh/) for two students. Word identification showed limited gains. Conclusions: Adapted Hebrew vowel-based instruction supported a functional relationship in improving vowel performance among MV adolescents with autism and ID, with positive improvement in syllable (CV) identification for two students. Limited word-level gains underscore the need for further research on contextual and semantic supports beyond phonics decoding. Teachers' positive responses and sustained student engagement demonstrate the feasibility of this approach for this underrepresented population.