Given that the best measures of presence currently available are subjective self-assessments, it is desirable to attempt to develop reliable, repeatable, quantitative measures. We present the results of two experiments intended to decompose presence into measurable subcomponents; attention and spatial comprehension. The first experiment was a conventional dual-task study where we measured attentional demands of competing virtual and real world experiences. The results suggest that attention may

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... be a reasonable quantitative measure of presence. The study also showed that the use of sound increased the level of engagement experienced by participants. The second study attempted to correlate spatial knowledge acquisition with presence. The only component of spatial knowledge acquisition that was positively affected was landmark knowledge which improved with the addition of semantic verbal information. The data does not generally support a relationship between spatial comprehension and presence but again, it was found that the use of sound increased participants' sense of engagement in the virtual world. There are certainly other candidate subcomponents of presence but we began our investigation here. An expanded investigation towards the development of an aggregate quantitative measure of presence is suggested. Quantitative Measures of Presence