Speech Onset Time at Home or in the Lab: The Role of Testing Environment and Experimenter Presence.

Psycholinguistic research has become increasingly reliant on online experimentation, which has also grown more attractive for studying speech production. However, concerns remain about data quality in online settings and the absence of experimenters to ensure participant engagement. In this pre-registered study, we used two tasks—picture naming and reading aloud—to test whether the lexical frequency effect (Low Frequency words > High Frequency words) on speech onset times can be reliably detected in online environments (run at Home), both with and without experimenter supervision. Participants completed the same tasks under four conditions, varying by Supervision (between-subjects: Supervised vs. Unsupervised) and Environment (within-subjects: Lab vs. Home): Lab-Supervised, HomeSupervised, Lab-Unsupervised, and Home-Unsupervised. Frequency effects emerged across all conditions except Home-Supervised for the reading aloud task, where the effect was in the expected direction but non-significant (~12 ms). All other conditions yielded consistent frequency effects (~17–38 ms), comparable to previous online and lab-based findings. Notably, participants were faster at home than in the lab (~10 ms), and unsupervised settings yielded the largest effect sizes, suggesting that experimenter presence may inadvertently dampen subtle effects, possibly due to increased self-monitoring or reduced comfort. These findings validate the use of online platforms for speech production research and highlight the nuanced influence of supervision on experimental outcomes.