Immersion, Presence, and Performance in Virtual Environments
Title Page
1. Introduction: Is VR better than a workstation?
This paper describes an experiment to compare task performance of twenty
four subjects with respect to immersive and non-immersive participation
and interaction in a virtual environment (VE). Subjects participated in
and observed a sequence of events played out in relation to a complex geometrical
structure, and their task was the subsequent reproduction of those events
with respect to the real world equivalent of that structure. Half the subjects
participated in a visually immersive VE, and the remainder in a non-immersive
VE. A secondary independent variable was the realism of the displayed environment.
The task involved the reproduction of moves of pieces in the Tri-Dimensional
chess game popularised in the TV series Star Trek. One inspiration of this
work was the question posed by Mizell,
Jones, Jackson and Picket (1995): "Is VR better than a workstation?"
For our work this question breaks down into a number of components:
(a) Cognition of Geometric Structure
We want to know whether people can benefit significantly with respect to
their understanding of geometric structure when they are immersed in and
interact with a VE compared to the use of conventional workstations and
displays. This is important for our work on geometrical modeling, where
participants are immersed in a VE in order to create free-form surfaces
(Slater and Usoh, 1995). Here
the issue is to gain insight as to whether immersive virtual environments
(IVEs) can show any benefit with respect to their understanding of the complex
geometrical structure of such surfaces and objects composed from these surfaces.
This is similar to the question posed by Mizell et. al., who aim to "experimentally
assess and quantify, if possible, a difference in a user's being able to
comprehend a complex three-dimensional scene between viewing it in 2-D on
a workstation screen and viewing the scene via an immersive VR system...".
The Mizell work showed subjects complex 3D shapes in reality, on a conventional
workstation display, and through a stereo BOOM head-coupled device. The
shapes were of three levels of difficulty. Each subject had to reproduce
the shape in reality (using provided basic shapes) while being able to observe
the baseline shapes from one of the three sources. Each subject successively
used each method (reality, workstation, BOOM) in a pre-assigned randomly
determined order. The response variable was time to completion of the shape.
The results showed that observing the shape in reality was always the fastest
method, and except for the simplest shape, looking at the workstation display
was more effective than looking through the BOOM. As the authors noted,
however, there were several problems with this experiment, including the
fact that looking at the workstation display was a faster operation than
looking through the BOOM (which could often get into awkward positions).
Moreover, this experiment involved no interactive manipulation of objects
in the VE.
(b) Knowledge Transfer
Here the question is whether skills or knowledge gained in a virtual environment
can be successfully transferred to the real world. Suppose that a person
learns to perform some task in a virtual environment, does immersion improve
the chance of transfer of such knowledge to the real world? A previous attempt
to study this (Slater, Alberto and
Usoh, 1995) involved a number of subjects who walked through a virtual
building immersively, and control group subjects who did the same non-immersively.
The task involved finding a particular object within the virtual building.
A response variable was the time it took them to find this object in the
corresponding real building. No significant difference was found between
performance for immersed and non-immersed subjects. However, the evidence
suggested that those individuals with a high sense of presence, whether
in an immersive or non-immersive system, achieved better performance overall.
In this study also there was no interaction with objects in the virtual
environment other than walkthrough.
Wilson and Foreman (1993) considered
a similar problem comparing observations from subjects in non- immersive
virtual and the corresponding real environments. They concluded
that "... the overall picture is one of little difference between spatial
information gained from exploring the computer simulation of the building
and real exploration." If this is the case for virtual non-immersive
and real environments, then is not surprising that this may the case for
non-immersive and virtual immersive environments. The tasks of the subjects
of Wilson and Foreman, however, also did not involve interaction with the
environment.
(c) Immersion and Performance Within the Virtual Environment
The studies reported above concentrated on the effects of immersion in relation
to tasks later performed in the real world. It is also important to consider
these effects in relation to tasks performed in a VE. Chung
(1992) considered various different models of immersion on targeting
of treatment beams in radiotherapy treatment planning. All subjects used
a HMD but in some models the HMD was enabled for head-tracking, and in other
models steering was achieved through hand-held devices. All subjects used
each steering mode. The experimental study found no difference between the
head-tracked steering modes and the non-head tracked modes. Pausch,
Shackelford and Proffitt (1993) studied the effect of immersion on a
target search task in a study where one group used a head-tracked HMD for
target location, and another used a HMD with head tracking disabled with
viewing controlled through the use of a hand-tracked device. The result
was that the head-tracked group achieved nearly twice the speed of target
location compared to the hand-trackers.
None of the studies reported above included interaction, that is, manipulation
of objects in the virtual environment. Also the use of the phrase "task
performance" in relation to VEs is sometimes ambiguous. There is clearly
the distinction between effectiveness of task performance within the VE,
and effective performance in relation to some task performed in the real
world but in relation to a VE experience. In this paper we consider the
latter case, and also have an experimental scenario that includes some interaction
with objects in the VE.
In the next Section we provide more explicit explanations for the terms
immersion, presence and the relationship between these and "performance".
The details of the experiment are provided in Section 3, and results in
Section 4. Section 5 provides the overall conclusions of this study and
some consideration of the problems of experimental design and further work.