Effects of sensory information and prior experience on direct subjective ratings of presence

We report three experiments using a new form of direct subjective presence evaluation that was developed from the method of continuous assessment used to assess television picture quality. Observers were required to provide a continuous rating of their sense of presence using a handheld slider. The first experiment investigated the effects of manipulating stereoscopic and motion parallax cues within video sequences presented on a 20 in. stereosco pic CRT display. The results showed that the presentation of both stereosco pic and motion-parallax cues was associated with higher presence ratings. O ne possible interpretation of Experiment 1 is that CRT displays that contai n the spatial cues of stereoscopic disparity and motion parallax are more i nteresting or engaging. To test this, observers in Experiment 2 rated the s ame stimuli first for interest and then for presence. The results showed th at variations in interest did not predict the presence ratings obtained in Experiment 1. However, the subsequent ratings of presence differed signific antly from those obtained in Experiment 1, suggesting that prior experience with interest ratings affected subsequent judgments of presence. To test t his, Experiment 3 investigated the effects of prior experience on presence ratings. Three groups of observers rated a training sequence for interest, presence, and 3-Dness before rating the same stimuli as used for Experiment s 1 and 2 for presence. The results demonstrated that prior ratings sensiti ze observers to different features of a display resulting in different pres ence ratings. The implications of these results for presence evaluation are discussed, and a combination of more-refined subjective measures and a bat tery of objective measures is recommended.