THE USE OF PUPILLOMETRY TO STUDY MENTAL DEMAND DURING SPEECH PRODUCTION IN NOISE

Understanding the cognitive demand required for implementing speech therapy techniques in real-world environments has significant clinical implications. This study used self-rating and pupillometry to investigate the mental demand associated with speaking differently in various noise conditions. Five speakers with healthy voices read aloud in casual and clear speech in quiet conditions and while listening to multi-talker (MT) noise, reversed two-talker (RevMT) noise, and speech-shaped (SS) noise. The speakers rated their perceived mental demand after each task using a modified NASA-TLX scale, while the change in their pupil size was monitored using an eye tracker. The results of this self-rating revealed that mental demand was highest in the MT noise condition, followed by RevMT noise. In contrast, SS noise did not significantly increase mental demand. Pupillometry data showed that the pupil dilation was greatest for the MT noise, for both casual and clear speech, corroborating the self-rating data. Interestingly, the dilation for clear speech was greater than for casual speech in quiet, but less in RevMT and SS noises. These findings illustrate a complex interaction between speech modification and acoustic environments and suggest the potential of pupillometry as an objective measure for quantifying mental demand in speech production.