Making Distance Judgements in Real and Virtual Environments: Does Order Make a Difference?

1
Making Distance Judgements in Real and Virtual
Environments Does Order Make a Difference?
James Cremer Joseph Kearney Computer Science
Department The University of Iowa james-cremer_at_uio
wa.edu, joe-kearney_at_uiowa.edu
Christine Ziemer Jodie Plumert Department of
Psychology The University of Iowa,
christine-ziemer_at_uiowa.edu, jodie-plumert_at_uiowa.e
du
Introduction Virtual environments are gaining
widespread acceptance as a tool for studying
human behavior (Loomis et al., 1999 Plumert et
al., 2004). But how well does behavior in virtual
environments correspond to behavior in the real
environment? Although virtual environments are an
exciting new medium for investigating
difficult-to-study problems, the results of such
experiments are of questionable value if virtual
environments lack ecological validity. One
critical aspect of behavior in both real and
virtual environments is distance perception.
Several recent studies suggest that people
underestimate distance in virtual environments
relative to the real environment (Loomis Knapp,
2003 Thompson et al., in press Willemsen
Gooch, 2002). The conclusion that people
underestimate distances in virtual environments
may be premature, however. To date, studies
examining distance perception in virtual
environments have all used head mounted display
(HMD) systems. In a recent study using a large
screen immersive display (LSID) system, Plumert,
Kearney, Cremer, and Recker (2005) found that
distance estimates did not differ across real and
virtual environments when people made estimates
in the real environment first. When people made
estimates in the virtual environment first,
however, estimates were significantly shorter in
the virtual than in the real environment. The
goal of this study was to further investigate how
the order in which people make judgments in real
and virtual environments influences their
distance estimates.
Experiment 1 Order Effects on Time-to-walk
Estimates Questions (1) How well do
time-to-walk estimates correspond in real and
virtual environments? (2)
Does the order in which an environment is
experienced affect distance estimations? Particip
ants Forty-eight undergraduates participated
for course credit. Environments Real
environment. The real environment was an open,
grassy lawn in front of a university building.
Virtual environment. The
virtual environment was a scene depicting the
real environment. This scene was displayed on
three 10-ft wide x 8-ft high screens placed at
right angles to each other. Participants stood
midway between the two side screens and 8 ft from
the front screen. High-resolution, textured
graphics were projected onto the screens (1280 x
1024), providing participants with 270 degrees of
nonstereoscopic, immersive visual imagery. The
viewpoint of the scene was adjusted for each
participants eye height. Participants viewed the
scene binocularly.
Real environment
Virtual environment
Design and Procedure Baseline walking. We first
obtained an estimate of each participants
typical walking speed by timing how long it took
each participant to walk between two points in a
hallway. Time-to-walk estimates. After the
baseline walking task, participants made
estimates of how long it would take them to walk
to targets in the real (RE) and virtual
environment (VE). Participants made two sets of
time-to-walk estimates in one of the following
conditions 1) RE first, VE second 2) VE first,
RE second 3) RE first, RE second or 4) VE
first, VE second. Participants viewed a person
(or an image of a person) standing on the lawn in
front of them. They started a stopwatch when they
imagined starting to walk and stopped the
stopwatch when they imagined reaching the person
(without looking at the stopwatch). Participants
made estimates of 6 randomly ordered distances in
both environments (20, 40, 60, 80, 100, 120
ft). Measures Actual time-to-walk. We estimated
the amount of time actually required to walk the
six distances for each participant by dividing
each actual distance by the participants
baseline walking speed. Time-to-walk estimates.
Each participant had 12 time-to-walk estimates,
representing the time elapsed between starting
and stopping the stopwatch for each distance in
each environment.
Results Q1 How well did estimates correspond
in the two environments? Time-to-walk estimates
did not differ significantly across the two
environments for either the first or the second
estimates (see Figures 1a 1b). Q2 Did the
order in which the environments were experienced
effect distance estimations? Although
time-to-walk estimates made first were smaller
(though not significantly so) in the virtual than
in the real environment, time-to-walk estimates
made second were virtually identical in the
real-real and real-virtual conditions. Summary
of Experiment 1 Time-to-walk estimates were
similar across the real and virtual environments.
Second estimates in the real and virtual
environments were almost identical when people
experienced the real environment first. This
suggests that experience with making distance
judgments in the real environment first leads to
improvements in distance judgments in the virtual
environment. In Experiment 2, we investigated
whether this improvement depends on making
judgments about identical scenes in both
environments.
25
20
15
Estimate (s)
10
5
0
20 ft
40 ft
60 ft
80 ft
100 ft
120 ft
Figure 1b. Mean time-to-walk estimates made
second