Effects of stereoscopic presentation, image motion, and screen size on subjective and objective corroborative measures of presence

Recently, we reported that group subjective measures of presence as well as observers' postural responses are sensitive to increasing the realism of a display with motion content, by the addition of stereoscopic information, using a 20-inch stereoscopic screen with an effective horizontal field of v iew of 28 deg. (Freeman, Avons, Meddis, Pearson, & IJsselsteijn, 2000). The experiment presented here employed a large projection display with a 50 de g. horizontal field of view showing a rally car traversing a curved track a t speed. The independent variables included image motion and stereoscopic p resentation as within-subjects factors and screen size as a between-subject s factor. Dependent variables included subjective measures of presence, vec tion, involvement, and sickness, as well as observers' lateral postural res ponses, which served as a candidate objective corroborative measure of pres ence. Results demonstrated a noisy yet positive effect of stereoscopic pres entation on the lateral postural responses. Post-test subjective ratings re vealed a significant effect of stereoscopic presentation on the subjective judgments of presence, but not on those of vection, involvement, or sicknes s. Image motion had a large and significant effect on the subjective judgme nts of presence, vection, and involvement. The effect of image motion was c onsiderably larger than that of stereoscopic viewing. By comparing results between experiments, a large effect of screen size on subjective presence r atings could be demonstrated, but only for the video stimulus that containe d motion. The postural response measure did not differentiate between scree n sizes, thus limiting its utility as an objective corroborative measure of presence, although further research is required to be able to be more firm in our conclusion regarding this issue.