Review of four studies on the use of physiological reaction as a measure of presence in stressful virtual environments.

A common measure of effectiveness of a virtual environment (VE) is the amount of presence it evokes in users. Presence is commonly defined as the sense of being there in a VE. There has been much debate about the best way to measure presence, and presence researchers need and have sought a measure that is reliable, valid, sensitive, and objective. We hypothesized that to the degree that a VE seems real, it would evoke physiological responses similar to those evoked by the corresponding real environment, and that greater presence would evoke a greater response. To examine this, we conducted four experiments, each of which built upon findings that physiological measures in general, and heart rate in particular, are reliable, valid, sensitive, and objective presence measures. The experiments compare participants' physiological reactions to a nonthreatening virtual room and their reactions to a stressful virtual height situation. We found that change in heart rate satisfied our requirements for a measure of presence, change in skin conductance did to a lesser extent, and that change in skin temperature did not. Moreover, the results showed that significant increases in heart rate measures of presence appeared with the inclusion of a passive haptic element in the VE, with increasing frame rate (30 FPS > 20 FPS > 15 FPS) and when end-to-end latency was reduced (50 ms > 90 ms).