Presence

1
Presence

• Why talk about it
• How to measure it
• Where is it useful

2
Presence

• Sense of being physically present in a computer
  generated or remote environment (Sheridan,
  1992).

3
Open Questions

• Is there a definition of presence that is
  sufficiently operational and quantitative to be
  useful?
• What are the factors that create a sense of
  presence?
• Are there subjective and objective measures that
  can quantify presence?

4
Open Questions (cont.)

• Are there applications for which a sense of
  presence actually improves operator performance?
• Are there applications for which presence is a
  necessary ingredient? If so, how are these
  applications different from applications for
  which a more traditional display system is just
  as effective?

5
Sheridan (1992)
Sensory Information

• Three measurable physical variables that
  determine presence
• extent of sensory information
• control of sensors relative to environment
• ability to modify physical environment.

Ability to Modify Environment
Control of Sensors
6
Zeltzers AIP Cube

• Autonomy - Ability to react to events and
  stimuli.
• Interaction - Degree of access to the parameters
  or variables of an object
• Presence - Number and fidelity of the sensory
  input and output channels

VR
Autonomy
Presence
Interaction
7
How to measure Presence?

• Subjective measures
• Psychophysical measures
• Objective measures

8
Subjective measures
To what extent did you experience a sense of
being really there inside the virtual
environment? A little A lot 1 2 3 4 5 6 7
How realistic was your interaction with the
virtual objects? A little A
lot 1 2 3 4 5 6 7
9
Psychophysical measures

• Generally, psychophysical techniques are used to
  relate the physical magnitude of a stimulus with
  the observers subjective rating of the stimulus
  magnitude.
• Example R f(S) where R is 1-7 feeling of
  being present and S is a screen resolution or
  lag time.

10
Objective measures

• Physiological measures
• Performance measures

11
Physiological measures

• Just as humans experience changes in
  physiological parameters in response to novel or
  unusual stimuli in the real world, given
  sufficiently realistic stimuli in a virtual
  environment, the human should experience similar
  physiological changes.
• Cardiovascular, Respiratory,
• Nervous, Sensory,
• Blood Chemistry

12
Wiederhold with Fear of Flying Patients in VR
Physiological measures Not Anxious
Anxious
Subjective Measures Not Anxious Anxious
13
Performance measures

• Behavior
• Suspension of belief
• Ducking
• Socially conditioned reactions

14
What seems to be true?

• A person's experience of a situation in a virtual
  environment may evoke the same reactions and
  emotions as the experience of a similar
  real-world situation. This may be true even when
  the virtual environment does not accurately or
  completely represent the real-world situation.

15
What seems to be true? (cont.)

• Each person brings their own Gestalt into a
  virtual reality experience.
• Cued Gestalt Larry Hodges

16
What seems to be true? (cont.)

• A primary difference between the experience of an
  event in a virtual environment and the experience
  of the same event in a real environment is in the
  intensity or vigor of the experience.

17
What seems to be true? (cont.)

• A person's perceptions of real-world situations
  and behavior in the real-world may be modified
  based on his experiences within a virtual world.

18
What seems to be true? (cont.)

• Virtual reality is consequence-poor relative to
  reality.

19
Presence?
Fidelity and attention to Sensory Channels
Gestalt
Consequences of Actions
20
Why is this important?

• Therapy
• Pain control
• Rehabilitation

• Entertainment
• Training
• Education