This study aimed to investigate the cognitive demand associated with changing the mode of speech production. The participants were fifteen healthy college students. The participants performed a modified Simon task, which required them to respond to the presentation of a red or blue square on the left or right side of a computer screen by pressing a key corresponding to the color. Participants performed the task in silence and while counting in three modes: habitual speech, whisper, and clear speech. Each condition was repeated three times in random order. Reaction time and error rate were used as the outcome measures. Results showed that the mean reaction time was significantly longer for the whisper and clear speech conditions compared to the baseline (i.e., no counting) and habitual speech conditions. These findings suggest that speaking in different speech production mode requires greater cognitive load, and reaction time to the secondary tasks could serve as a proxy for the cognitive load. The presentation will discuss the implications of the findings for training occupational voice users and individuals with voice and speech disorders.