Investigating the Effects of Paralinguistic Configuration in Background Human Speech on Attention: Protocol for a...

Background noise is common in everyday environments; yet, its effects on attention vary according to task demands, individual characteristics, and properties of the noise itself. Previous research has largely focused on music, nonspeech noise, or intelligible speech, leaving the effects of paralinguistic components of human speech (eg, tone, pitch, and rhythm) difficult to disentangle from linguistic content.

This study aims to investigate whether paralinguistic characteristics of semantically inaccessible background speech influence attentional performance. Specifically, it will compare focused and diffused vocal stimuli that differ in paralinguistic configuration, with silence included as a reference condition, while also examining physiological responses and individual differences.

Adults aged 18 years or older (target n=60) will complete one 120-minute laboratory session. In a counterbalanced within-subject design, participants will perform attention-related tasks under 3 auditory conditions: silence, focused vocal stimuli, and diffused vocal stimuli. The primary outcome will be the concentration performance (CP) score of the d2 Test of Attention, and reading comprehension accuracy will be a secondary behavioral outcome. Pupillometry, electrodermal activity (EDA), and blood volume pulse (BVP) will be recorded continuously, with mean pupil diameter, phasic EDA response rate, and the root-mean-square of successive differences (RMSSD) designated as prespecified secondary physiological outcomes. Individual differences in working memory capacity, noise sensitivity, attention-deficit hyperactivity disorder (ADHD) symptomatology, sleep quality, and mood will be assessed as potential moderators. The primary confirmatory analysis will use a linear mixed-effects model with auditory condition as a fixed effect, block position as a covariate, and participant as a random intercept. The prespecified primary contrast will compare the focused and diffused vocal conditions at α=.05. Focused versus silence and diffused versus silence will be examined as secondary contrasts with Holm adjustment for multiple comparisons. The Holm procedure will be used to adjust for multiple testing across the prespecified physiological outcomes, while moderation analyses will be considered exploratory. The protocol was refined following a formative pilot with 9 participants using an abbreviated 2-block procedure.

Ethics approval was granted in June 2026. No participants have been recruited for the full study described in this protocol. Recruitment is scheduled to begin in September 2027, with data collection projected to conclude in September 2029, and data analysis expected to be completed by September 2030. Dissemination of the results is anticipated by September 2031.

This protocol provides a reproducible approach for investigating whether paralinguistic characteristics of semantically inaccessible background speech influence attention and for examining accompanying physiological responses. The study will test whether attentional performance differs between focused and diffused vocal conditions and explore individual characteristics that may moderate these responses. The findings may inform future research on auditory distraction and the design of occupational and educational environments.