1. Presence in Virtual Environments © Mel Slater 2001

2. Outline Presence and hypothesis selection Measurement Domain The Usual Results

3. Presence and Hypothesis Selection Current in perceptual theory – Perceptual system selects between competing hypotheses (Richard Gregory) – Scanpath theory suggests that perceptual system is top-down driven (Lawrence Stark) We see what we expect to see.

4. Competing Signals Presence is only interesting when there are competing signals from at least two ‘environments’. How will you act?

5. Presence as a Selector Given competing signals – Choose action based on selection amongst hypotheses I am in this world I am in that world (I am mixed up) Hypotheses relating to the fundamental question: – Where am I? Totality of signals form into one of several ‘gestalts’ (‘environments’).

6. Actions Actions may be – Involuntary/Voluntary – Conscious / Unconscious – Supported / Denied Obviously not ‘real’ – But act as if real

7. Implications for Measurement Questionnaires deliver an integration over time of conscious/voluntary/supported responses. Behavioural measures require imposition of events that may not be part of the environment (eg, looming). Deliberate introduction of conflicting signals (eg, shadows). Physiological measures are in response to specific types of event (anxiety provoking).

8. Measurement BIPs ‘breaks in presence’ – possible to build a measure based on when these occur. Sampling (attentional resources). Behavioural observation. Unification of BIPs + physiological?

9. Domain Responses Reading a novel -> physiological Movie -> + some body movement 3D movie -> + more body movement Game -> + more body movement Immersive VR -> + total body movement “Fire!” – In a movie or computer game, no one would rush out of the room – In immersive VR – they might do so!

10. The Usual Results The norm is that in a ‘good’ immersive VR – Reported presence is often very high!!! CAVE almost puts us out of business! Few BIPs No BIPs when engaging. Why?

11. Evolutionary Argument In all of personal and evolutionary history: – What we ‘see’ is where we are … Parallax Responsive actors Spatial extension Interaction – … and where we act At some deep level – Our mind does not know about VR!

12. Perceptual Augmentation What we see is where we are, but… – Where we are is in our heads – (Stark:)“Virtual reality works because reality is virtual.” Very simple cues required to trigger presence – Perceptual mechanisms do the rest – Provided that the VR is ‘good’. What is ‘good’?