Effect of experimentally induced stress on vocal parameters.
In a factorially designed experiment the factors Mode of Stress (cognitive vs. emotional) and Degree of Stress (low vs. high) were studied in their effect on phonatory and articulatory processes during speech production in groups of male and female students (factor Sex) selected to represent three types of personality (factor Coping Style: low anxiety, high anxiety, anxiety denying). Using digital speech analysis procedures, mean F0, F0 floor, formant location, and spectral energy distribution were extracted from the experimental speech samples. Although mean F0 did not covary with stress manipulation, F0 floor of high-anxious and anxiety-denying subjects increased with stress, probably due to physiologically based changes in muscle tension. For articulatory processes, as measured through formant location and spectral composition, significant changes were found for females. For anxiety-denying female subjects, precision of articulation increased under cognitive stress and decreased under emotional stress. The results are interpreted in terms of differential susceptibility to stress.