A virtual-reality (VR) cognitive pupillometry analysis of auditory and visual phonemic awareness tasks involving ‘th’ sound variations

Rooted in the Cognitive Load (CL) and Dual Coding theories, this sequential explanatory study examined the CL levels experienced by 36 available Iranian pre-intermediate English as a Foreign Language (EFL) learners in auditory and visual Phonemic Awareness Tasks (PATs). The PATs focused on 'th' sound variations that were specifically challenging for Persian speakers of English. Participants were divided into two equal groups. The first group underwent auditory and visual PATs (i.e., picture sorting and word discrimination). The second group faced auditory PATs only (i.e., rhyme recognition and sound isolation) structured around voiced and voiceless ‘th’ sounds. In the qualitative phase, 8 participants were randomly interviewed to discover the potential reasons behind various levels of CL measured in certain PATs. A Virtual Reality (VR) cognitive pupillometry analysis was performed for two groups in an immersive VR environment using VR Head-Mounted Displays (VR-HMDs) and Tobii Nexus software, followed by thematic analysis. GazeMetrics strategies were employed to validate and ensure the reliability of the data collection process. The quantitative results demonstrated (a) no critical differences regarding the CL experienced by the participants in each group concerning voiced vs. voiceless’ th’ PATs and (b) higher levels of CL (increased pupil diameter, decreased blink rates, and increased gaze pattern or fixation duration) among participants in the auditory PATs group compared to the ones in the auditory and visual PATs group. Besides, qualitative findings identified the following factors as the most probable causes of the observed differences in CL levels among participants: (a) segmental differences, (b) phonological transfer, (c) phonological fossilization, (d) working memory constraints, (e) cognitive flexibility, and (f) task delivery methods. This study contributes to cognitive phonology, phonological processing, perceptual-motor language functions, and English material development.