A virtual presence counter

This paper describes a new measure for presence in immersive virtual enviro nments (VEs) that is based on data that can be unobtrusively obtained durin g the course of a VE experience. At different times during an experience. a participant will occasionally switch between interpreting the totality of sensory inputs as forming the VE or the real world. The number of transitio ns from virtual to real is counted, and, using some simplifying assumptions , a probabilistic Markov chain model can be constructed to model these tran sitions. This model can be used to estimate the equilibrium probability of being "present" in the VE. This technique was applied in the context of an experiment to assess the relationship between presence and body movement in an immersive VE. The movement was that required by subjects to reach out a nd touch successive pieces on a three-dimensional chess board. The experime nt included twenty subjects. ten of whom had to reach out to touch the ches s pieces (the active group) and ten of whom only had to click a handheld mo use button (the control group). The results revealed a significant positive association in the active group between body movement and presence. The re sults lend support to interaction paradigms that are based on maximizing th e match between sensory data and proprioception.