Transcutaneous Vagus Nerve Stimulation (tVNS) and Stress Regulation During Performance Tasks

This study is a laboratory-based, randomized, double-blind experiment designed to examine whether non-invasive transcutaneous vagus nerve stimulation (tVNS) influences state anxiety and physiological arousal during performance-related stress. Participants will be randomly assigned to one of four conditions in a 2 × 2 between-subjects factorial design: Device Condition: Active tVNS Placebo (inactive) tVNS Task Condition: Stress Task (Modified Trier Social Stress Test speech preparation) Control Task (Non-evaluative writing task) The device condition is double blind. Half of the devices are configured by the manufacturer to deliver active stimulation to the auricular branch of the vagus nerve via the left ear. The remaining devices are configured to deliver brief initial stimulation that ramps down to zero (placebo condition). Neither participants nor experimenters are aware of device assignment during the session. After informed consent and baseline measures, participants complete a quiet baseline period during which heart rate and state anxiety are assessed. Participants then wear the tVNS device during structured laboratory tasks. In the stress condition, participants are instructed to prepare a five-minute speech to be delivered before evaluators and recorded for assessment. The preparation phase is modeled after the Trier Social Stress Test and is designed to induce anticipatory evaluative stress. The speech is not ultimately delivered. State anxiety and heart rate are measured during preparation and immediately afterward. In the control condition, participants complete a non-evaluative writing task on the same topic without evaluative framing. Physiological and self-report measures are collected at matched time points. The primary outcome measure is state anxiety assessed using the short-form State-Trait Anxiety Inventory (STAI). Secondary outcomes include heart rate measured during baseline, task preparation, and recovery periods. Additional measures include dispositional stress reactivity, which will be examined as a potential moderator of stimulation effects. The study is designed to determine whether active tVNS reduces subjective anxiety and physiological arousal during evaluative stress compared to placebo stimulation and to assess whether effects differ as a function of individual differences in stress reactivity. Participation consists of a single laboratory session lasting approximately 45 minutes.