Reported presence data was gathered in both experiments described in this chapter. The order of conditions was counter-balanced across participants and (in Experiment AIE2) sessions. Each experiment gathered two reported presence ratings per condition, in order to examine test-retest reliability. Both experiments used the same procedure, except that Experiment AIE1 recorded two presence ratings per condition in a single session, and Experiment AIE2 recorded one presence rating per condition in each of two sessions. In Experiment AIE1, initial presence ratings were obtained for each of three conditions in random order. Immediately afterwards, presence ratings were obtained for the same three conditions in an independent random order.
Participants were familiarized with the general idea of presence prior to the experiment by the following written description.
Experiencing a virtual world can lead to a conflict in where you focus your attention. For instance, you may feel as if you are in the place suggested by the virtual world. At the same time, you may be aware of the contradictory fact that you are in the laboratory, wearing a head-mounted display. The following question assesses the extent to which you feel ``immersed'' in the virtual world, and whether the intensity of this feeling is different in the various conditions. There are no ``correct'' answers. Please make your ratings as honestly as possible. Pick a number between 1 and 7, where ``1'' means ``very little'' and ``7'' means ``very much so''.
Participants were also familiarized (prior to the experiment) with the particular presence question to be asked. The question was as follows:
For a discussion of this presence question, see Section 3.8.1.
When reported presence data was gathered, participants were seated in a chair which oscillated sinusoidally at .1 Hz, with an amplitude of 20/sec. They wore a Virtual Research VR4 HMD showing the (non-stereographic) scene oscillating sinusoidally at .1 Hz, with an amplitude of 30/sec. The inertial and vection stimuli were consistent (i.e., what one would expect in the real world). The visual amplitude was chosen for saliency, and the inertial amplitude was chosen to be in the upper range of inertial amplitudes likely to be experienced during the visual-inertial nulling measure trials. The non-equality of the inertial and visual amplitude was deliberate, to be consistent with the normal state of affairs in the visual-inertial nulling measure trials.
Participants were asked to observe each condition, which were shown for one minute each. Immediately afterwards, participants were exposed to the same conditions, and, after 10 seconds, asked the presence question about each condition.
Before obtaining repeated measures for the same condition, participants were instructed to answer the question in the same way if they felt the same as the first time, and differently if their impressions had changed.