1 Analysis of Physiological Responses to a Social Situation in an Immersive Virtual Environment Slater M.#, Guger C.*, Edlinger G.*, Leeb R.+, Pfurtscheller G.+, Antley, A.#, Garau, M.#, Brogni A.#, Friedman D.#, #Department of Computer Science, University College London, United Kingdom *Guger Technologies OEG, Herbersteinstrasse 60, A-8020 Graz, Austria, www.gtec.at +Institute of Human-Computer Interfaces, Graz University of Technology, Austria. Abstract An experiment was conducted in a Cave-like environment to explore the relationship between physiological responses and each of breaks in presence, and utterances by virtual characters towards the participants. Twenty people explored a virtual environment (VE) that depicted a virtual bar scenario. The experiment was divided into a training and an experimental phase. During the experimental phase breaks in presence (BIPs) in form of whiteouts of the VE scenario were induced for 2 seconds at four equally spaced times during the approximate 5 minutes in the bar scenario. Additionally 5 virtual characters addressed remarks at the subjects. Physiological measures including ECG and GSR were recorded throughout the whole experiment. The heart rate, the heart rate variability and the event-related heart rate changes were calculated from the acquired ECG data. The frequency response of the GSR signal was calculated with a wavelet analysis. The study shows that the heart rate and heart rate variability parameters vary significantly between the training and experimental phase. GSR parameters and event-related heart rate changes show the occurrence of breaks in presence. Event-related heart rate changes also signified the virtual character utterances. There were also differences in response observed between more and less social phobic participants. Keywords: virtual environment, presence, breaks in presence, galvanic skin response, ECG, heart rate variability