Browse Theses

Virtual environments (VEs) are one of the most advanced human-computer interface to date. A common measure of the effectiveness of a VE is the amount of presence it evokes in users. Presence is commonly defined as the sense of being there in a VE.

In order to study the effect that technological improvements such as higher frame rate, more visual realism, and lower lag have on presence, we must be able to measure it. There has been much debate about the best way to measure presence, and we, as presence researchers, have yearned for a measure that is: (1)  Reliable —produces repeatable results, both from trial to trial on the same subject and across subjects; (2)  Valid —measures subjective presence, or at least correlates well with established subjective presence measures; (3)  Sensitive —is capable of distinguishing multiple levels of presence; and (4)  Objective —is well shielded from both subject bias and experimenter bias.

We hypothesize that to the degree that a VE seems real, it will evoke physiological responses similar to those evoked by the corresponding real environment, and that greater presence will evoke a greater response. Hence, these responses serve as reliable, valid, sensitive, and objective measures of presence.

We conducted three experiments that support the use of physiological reaction as a reliable, valid, sensitive, and objective measure of presence. We found that change in heart rate was the most sensitive of the physiological measures (and was more sensitive than most of the self-reported measures) and correlated best among the physiological measures with the reported presence measures. Additionally, our findings showed that passive haptics and fame rate are important for evoking presence in VEs. Inclusions of the 1.5-inch wooden ledge into the virtual environment significantly increased presence. Also, for presence evoked: 30 FPS (frames per second) > 20 FPS > 15 FPS. In conclusion, physiological reaction can be used as a reliable, valid, sensitive, and objective measure of presence in stress-inducing virtual environments.