Vocal function in introverts and extraverts during a psychological stress reactivity protocol.

PURPOSE To examine the proposal that introversion predictably influences extralaryngeal and vocal behavior in vocally healthy individuals compared with individuals with extraversion and whether differences are of a nature that may support a risk hypothesis for primary muscle tension dysphonia. METHOD Fifty-four vocally healthy female adults between the ages of 18 and 35 years were divided into 2 groups: introversion (n = 27) and extraversion (n = 27). All participants completed a psychological stress reactivity experiment. Before, during, and after the stressor (public speaking), participants were assessed on extralaryngeal muscle activity (surface electromyography: submental, infrahyoid; control site: tibialis anterior), perceived vocal effort, and vocal acoustics (fundamental frequency and intensity). RESULTS Participants in the introversion group exhibited significantly greater infrahyoid muscle activity throughout the protocol and during perceived stress than participants in the extraversion group. For both groups, perceived vocal effort significantly increased during stress, and acoustic measures significantly decreased. Infrahyoid muscle activity during the stress phase was significantly correlated with introversion and Voice Handicap Index scores but not with vocal effort scores. CONCLUSIONS The data provided evidence of distinct differences in extralaryngeal behavior between introverts and extraverts. The findings are consistent with the trait theory of voice disorders (Roy & Bless, 2000).