Mapping Four Decades of Think-Aloud Protocol Research in L1 and L2 Reading: A Systematic Scoping Review of Methodological Practices and Debates

This systematic scoping review maps the extent, range, and nature of empirical and methodological literature on think-aloud (verbal protocol) research in L1 and L2 reading contexts published between 1984 and 2025. Think-aloud protocols have been widely employed in reading strategy research for four decades, yet no systematic synthesis has transparently mapped how this methodology has been implemented, reported, and evaluated across the literature. Existing narrative reviews have provided valuable guidance but lack the transparent search and selection processes required to assess their comprehensiveness or representativeness. The review is conducted in accordance with the PRISMA extension for Scoping Reviews (PRISMA-ScR; Tricco et al., 2018) and follows the five-stage scoping review framework of Arksey and O'Malley (2005) as refined by Levac et al. (2010). Systematic searches are conducted in five electronic databases — ERIC, PsycINFO, Web of Science Core Collection, Scopus, and Linguistics and Language Behavior Abstracts (LLBA) — supplemented by forward and backward citation searching of nine anchor texts in the field. The review addresses four objectives: (1) to systematically identify and map the full range of empirical studies and methodological discussions employing think-aloud protocols in L1 and L2 reading research published between 1984 and 2025; (2) to characterise methodological reporting practices across included studies with respect to seven key stages — training, data collection, transcription, segmentation, coding, reliability, and reporting; (3) to synthesise the theoretical and empirical debates regarding think-aloud validity, reactivity, and appropriate use; and (4) to derive evidence-based methodological guidelines from the synthesis of best practices identified across the corpus. Expected outcomes include: the first systematically derived characterisation of methodological reporting practices across four decades of think-aloud reading research; quantification of critical reporting gaps (particularly reliability reporting and training description); an evidence-based seven-stage methodological framework and checklist for future research; and a comprehensive, PRISMA-ScR-compliant synthesis suitable for submission to an SSCI-indexed journal in applied linguistics or reading research.