The Need for a Neutral Speaking Period in Psychosocial Stress Testing

Tasks such as the Trier Social Stress Test, narrative recall, and some cognitive challenges require participants to speak in order to measure acute physiological responses to induced stress. Typically, the physiological measures during the stressed state are compared to a silent baseline period. This does not differentiate between stress that is induced by emotion and stress due to the physical act of vocalization. We modified a psychosocial stress task for 41 participants to add a period of neutral speaking. We hypothesized that there would be significant differences in physiological measures between the silent baseline and neutral speaking periods, and that these differences would explain a substantial proportion of the stress response traditionally attributed to emotion. Blood pressure, skin conductance level, respiration rate, salivary alpha-amylase, and high frequency heart rate variability showed significant changes during the neutral speaking period compared to a silent baseline, demonstrating the need for this control. Of the magnitude of physiological response which would have typically been attributed to emotion, 36-77% was due to vocalization alone. In stress-inducing tasks that require speaking, care should be taken in study design to account for the physiological impact of speech.