Validation of a New Stress Induction Protocol Using Speech Improvisation (IMPRO)

<b>Background:</b> Acute stress induction is essential in psychology research for understanding physiological and psychological responses. In this study, 'acute stress' refers to a short-term, immediate stress response-distinct from chronic, long-term stress exposure. Traditional methods, such as the Trier Social Stress Test (TSST), have ecological validity and resource-efficiency limitations. This study introduces the Interactive Multitask Performance Response Observation (IMPRO) protocol, a novel stress-induction method utilizing speech improvisation in a dynamic and unpredictable social setting. <b>Methods:</b> Thirty-five healthy adults (aged 18-38 years; 19 males, 16 females) participated in the study. The IMPRO protocol consisted of three speech improvisation tasks with increasing cognitive and social stressors. Salivary cortisol was used as a biochemical marker of acute stress, while electrodermal activity (EDA) provided real-time autonomic arousal measurements. Stress responses were assessed using paired <i>t</i>-tests for cortisol levels and repeated-measures ANOVA for EDA variations across experimental stages. <b>Results:</b> Salivary cortisol levels significantly increased from baseline (M = 2.68 nM, SD = 0.99) to post-task (M = 3.54 nM, SD = 1.25, <i>p</i> = 0.001, Cohen's d = 0.59), confirming hypothalamic-pituitary-adrenal (HPA) axis activation. EDA showed a significant rise during the anticipation phase (<i>p</i> < 0.001), peaking at the final task and decreasing during recovery (η² = 0.643). <b>Conclusions:</b> The IMPRO protocol effectively induces acute stress responses, providing a scalable, ecologically valid alternative to traditional stress paradigms. Its low-cost, adaptable design makes it ideal for research in psychology, neuroscience, and behavioral sciences. Future studies should explore its application in clinical populations and group settings.