Transcript presence - UCL Computer Science

Presence in Virtual
Environments
© Mel Slater 2001
Outline

Presence and hypothesis selection
 Measurement
 Domain
 The Usual Results
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.
Competing Signals

Presence is only interesting when there are
competing signals from at least two
‘environments’.
 How will you act?
Presence as a Selector

Given competing signals
– Choose action based on selection amongst hypotheses
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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’).
Actions

Actions may be
– Involuntary/Voluntary
– Conscious / Unconscious
– Supported / Denied

Obviously not ‘real’
– But act as if real
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).
Measurement
BIPs ‘breaks in presence’ – possible to build
a measure based on when these occur.
 Sampling (attentional resources).
 Behavioural observation.
 Unification of BIPs + physiological?
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Domain Responses
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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!
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?
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!
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’?