<s>
Virtual	B-Application
reality	I-Application
sickness	I-Application
,	O
or	O
VR	B-Application
sickness	I-Application
occurs	O
when	O
exposure	O
to	O
a	O
virtual	B-General_Concept
environment	I-General_Concept
causes	O
symptoms	O
that	O
are	O
similar	O
to	O
motion	O
sickness	O
symptoms	O
.	O
</s>
<s>
Common	O
causes	O
are	O
low	O
frame	O
rate	O
,	O
input	B-Application
lag	I-Application
,	O
and	O
the	O
vergence-accommodation-conflict	O
.	O
</s>
<s>
Virtual	B-Application
reality	I-Application
sickness	I-Application
is	O
different	O
from	O
motion	O
sickness	O
in	O
that	O
it	O
can	O
be	O
caused	O
by	O
the	O
visually-induced	O
perception	O
of	O
self-motion	O
;	O
real	O
self-motion	O
is	O
not	O
needed	O
.	O
</s>
<s>
It	O
is	O
also	O
different	O
from	O
simulator	O
sickness	O
;	O
non-virtual	O
reality	O
simulator	O
sickness	O
tends	O
to	O
be	O
characterized	O
by	O
oculomotor	O
disturbances	O
,	O
whereas	O
virtual	B-Application
reality	I-Application
sickness	I-Application
tends	O
to	O
be	O
characterized	O
by	O
disorientation	O
.	O
</s>
<s>
Virtual	B-Application
reality	I-Application
sickness	I-Application
may	O
have	O
undesirable	O
consequences	O
beyond	O
the	O
sickness	O
itself	O
.	O
</s>
<s>
For	O
example	O
,	O
Crowley	O
(	O
1987	O
)	O
argued	O
that	O
flight	B-Application
simulator	I-Application
sickness	O
could	O
discourage	O
pilots	O
from	O
using	O
flight	B-Application
simulators	I-Application
,	O
reduce	O
the	O
efficiency	O
of	O
training	O
through	O
distraction	O
and	O
the	O
encouragement	O
of	O
adaptive	O
behaviors	O
that	O
are	O
unfavorable	O
for	O
performance	O
,	O
compromise	O
ground	O
safety	O
or	O
flight	O
safety	O
when	O
sick	O
and	O
disoriented	O
pilots	O
leave	O
the	O
simulator	O
.	O
</s>
<s>
Although	O
the	O
evidence	O
for	O
performance	O
decrements	O
due	O
to	O
virtual	B-Application
reality	I-Application
sickness	I-Application
is	O
limited	O
,	O
research	O
does	O
suggest	O
that	O
virtual	B-Application
reality	I-Application
sickness	I-Application
is	O
a	O
major	O
barrier	O
to	O
using	O
virtual	O
reality	O
,	O
indicating	O
that	O
virtual	B-Application
reality	I-Application
sickness	I-Application
may	O
be	O
a	O
barrier	O
to	O
the	O
effective	O
use	O
of	O
training	O
tools	O
and	O
rehabilitation	O
tools	O
in	O
virtual	O
reality	O
.	O
</s>
<s>
Estimates	O
of	O
the	O
multi-study	O
incidence	O
and	O
main	O
symptoms	O
of	O
virtual	B-Application
reality	I-Application
sickness	I-Application
(	O
also	O
called	O
cybersickness	B-Application
)	O
have	O
been	O
made	O
.	O
</s>
<s>
Virtual	B-Application
reality	I-Application
sickness	I-Application
is	O
closely	O
related	O
to	O
simulator	O
and	O
motion	O
sickness	O
.	O
</s>
<s>
Sensory	O
conflict	O
theory	O
provides	O
a	O
framework	O
for	O
understanding	O
motion	O
sickness	O
;	O
however	O
,	O
it	O
can	O
be	O
applied	O
to	O
virtual	B-Application
reality	I-Application
sickness	I-Application
to	O
better	O
understand	O
how	O
it	O
can	O
occur	O
,	O
and	O
is	O
commonly	O
used	O
for	O
that	O
purpose	O
.	O
</s>
<s>
A	O
major	O
trigger	O
of	O
virtual	B-Application
reality	I-Application
sickness	I-Application
is	O
when	O
there	O
is	O
disparity	O
in	O
apparent	O
motion	O
between	O
the	O
visual	O
and	O
vestibular	O
stimuli	O
.	O
</s>
<s>
The	O
refresh	O
rate	O
of	O
on-screen	O
images	O
is	O
often	O
not	O
high	O
enough	O
when	O
VR	B-Application
sickness	I-Application
occurs	O
.	O
</s>
<s>
A	O
second	O
theory	O
of	O
motion	O
sickness	O
,	O
which	O
has	O
also	O
been	O
used	O
to	O
explain	O
virtual	B-Application
reality	I-Application
sickness	I-Application
,	O
is	O
the	O
theory	O
of	O
postural	O
instability	O
.	O
</s>
<s>
It	O
is	O
possible	O
to	O
induce	O
motion	B-Application
sickness	I-Application
in	I-Application
virtual	I-Application
reality	I-Application
when	O
the	O
frequencies	O
of	O
mismatched	O
motion	O
are	O
similar	O
to	O
those	O
for	O
motion	O
sickness	O
in	O
reality	O
,	O
such	O
as	O
seasickness	O
.	O
</s>
<s>
As	O
opposed	O
to	O
a	O
forward	O
viewing	O
angle	O
,	O
an	O
extreme	O
downward	O
angle	O
such	O
as	O
this	O
has	O
been	O
shown	O
to	O
markedly	O
increase	O
sickness	O
in	O
virtual	B-General_Concept
environments	I-General_Concept
.	O
</s>
<s>
Time	O
spent	O
immersed	O
in	O
a	O
virtual	B-General_Concept
environment	I-General_Concept
contributes	O
to	O
sickness	O
symptom	O
presence	O
due	O
to	O
the	O
increasing	O
effects	O
of	O
fatigue	O
on	O
the	O
user	O
.	O
</s>
<s>
In	O
January	O
2020	O
,	O
the	O
French	O
start-up	O
Boarding	O
Ring	O
,	O
known	O
for	O
their	O
glasses	O
against	O
motion	O
sickness	O
,	O
released	O
an	O
add-on	O
device	O
against	O
virtual	B-Application
reality	I-Application
sickness	I-Application
.	O
</s>
<s>
With	O
the	O
integration	O
of	O
virtual	O
reality	O
into	O
the	O
more	O
commercial	O
mainstream	O
,	O
issues	O
have	O
begun	O
to	O
arise	O
in	O
relation	O
to	O
VR	B-Application
sickness	I-Application
in	O
head-mounted	O
gaming	O
devices	O
.	O
</s>
<s>
Contemporary	O
VR	O
headsets	O
appear	O
to	O
induce	O
minimal	O
to	O
none	O
VR	B-Application
sickness	I-Application
.	O
</s>
<s>
While	O
certain	O
features	O
are	O
known	O
to	O
moderate	O
VR	B-Application
sickness	I-Application
in	O
head-mounted	O
displays	O
,	O
such	O
as	O
playing	O
from	O
a	O
seated	O
position	O
rather	O
than	O
standing	O
,	O
it	O
has	O
also	O
been	O
found	O
that	O
this	O
merely	O
puts	O
off	O
the	O
onset	O
of	O
sickness	O
,	O
rather	O
than	O
completely	O
preventing	O
it	O
.	O
</s>
<s>
Gaming	O
VR	O
specialists	O
argue	O
that	O
this	O
unique	O
brand	O
of	O
VR	B-Application
sickness	I-Application
is	O
only	O
a	O
minor	O
issue	O
,	O
claiming	O
that	O
it	O
disappears	O
with	O
time	O
spent	O
(	O
multiple	O
days	O
)	O
using	O
the	O
head-mounted	O
displays	O
,	O
relating	O
it	O
to	O
"	O
getting	O
your	O
sea	O
legs	O
"	O
.	O
</s>
<s>
Individuals	O
vary	O
widely	O
in	O
their	O
susceptibility	O
to	O
simulator	O
and	O
virtual	B-Application
reality	I-Application
sickness	I-Application
.	O
</s>
<s>
Some	O
of	O
the	O
factors	O
in	O
virtual	B-Application
reality	I-Application
sickness	I-Application
are	O
listed	O
below	O
:	O
</s>
<s>
It	O
has	O
been	O
suggested	O
that	O
virtual	B-Application
reality	I-Application
sickness	I-Application
might	O
follow	O
a	O
similar	O
pattern	O
,	O
but	O
more	O
recent	O
research	O
has	O
suggested	O
that	O
adults	O
over	O
the	O
age	O
of	O
50	O
are	O
more	O
susceptible	O
than	O
younger	O
adults	O
to	O
virtual	B-Application
reality	I-Application
sickness	I-Application
.	O
</s>
<s>
It	O
is	O
also	O
associated	O
with	O
increased	O
susceptibility	O
to	O
nausea	O
and	O
disorientation	O
symptoms	O
of	O
virtual	B-Application
reality	I-Application
sickness	I-Application
.	O
</s>
<s>
Flicker	O
fusion	O
frequency	O
threshold	O
:	O
Because	O
flicker	O
in	O
the	O
display	O
has	O
been	O
associated	O
with	O
increased	O
risk	O
of	O
virtual	B-Application
reality	I-Application
sickness	I-Application
,	O
people	O
with	O
a	O
low	O
threshold	O
for	O
detecting	O
flicker	O
may	O
be	O
more	O
susceptible	O
to	O
virtual	B-Application
reality	I-Application
sickness	I-Application
.	O
</s>
<s>
Ethnicity	O
:	O
Asian	O
people	O
may	O
be	O
more	O
susceptible	O
to	O
virtual	B-Application
reality	I-Application
sickness	I-Application
.	O
</s>
<s>
Chinese	O
women	O
appear	O
to	O
be	O
more	O
susceptible	O
to	O
virtual	B-Application
reality	I-Application
sickness	I-Application
than	O
European-American	O
and	O
African-American	O
women	O
;	O
research	O
suggests	O
that	O
they	O
are	O
more	O
susceptible	O
to	O
vision-based	O
motion	O
sickness	O
.	O
</s>
<s>
Tibetans	O
and	O
Northeast	O
Indians	O
also	O
appear	O
to	O
be	O
more	O
susceptible	O
to	O
motion	O
sickness	O
than	O
Caucasian	O
people	O
,	O
suggesting	O
that	O
they	O
would	O
also	O
be	O
more	O
susceptible	O
to	O
virtual	B-Application
reality	I-Application
sickness	I-Application
,	O
since	O
susceptibility	O
to	O
motion	O
sickness	O
predicts	O
susceptibility	O
to	O
a	O
wide	O
range	O
of	O
motion-sickness	O
related	O
disturbances	O
.	O
</s>
<s>
Experience	O
with	O
the	O
system	O
:	O
Users	O
seem	O
to	O
become	O
less	O
likely	O
to	O
develop	O
virtual	B-Application
reality	I-Application
sickness	I-Application
as	O
they	O
develop	O
familiarity	O
with	O
a	O
virtual	O
reality	O
system	O
.	O
</s>
<s>
Gender	O
:	O
Women	O
are	O
more	O
susceptible	O
than	O
men	O
to	O
virtual	B-Application
reality	I-Application
sickness	I-Application
.	O
</s>
<s>
Women	O
are	O
most	O
susceptible	O
to	O
virtual	B-Application
reality	I-Application
sickness	I-Application
during	O
ovulation	O
and	O
a	O
wider	O
field	O
of	O
view	O
is	O
also	O
associated	O
with	O
an	O
increase	O
in	O
virtual	B-Application
reality	I-Application
sickness	I-Application
.	O
</s>
<s>
In	O
more	O
recent	O
research	O
,	O
there	O
is	O
some	O
disagreement	O
as	O
to	O
whether	O
gender	O
or	O
sex	O
is	O
a	O
clear	O
factor	O
in	O
susceptibility	O
to	O
virtual	B-Application
reality	I-Application
sickness	I-Application
.	O
</s>
<s>
Health	O
:	O
Susceptibility	O
to	O
virtual	B-Application
reality	I-Application
sickness	I-Application
appears	O
to	O
increase	O
in	O
people	O
who	O
are	O
not	O
at	O
their	O
usual	O
level	O
of	O
health	O
,	O
suggesting	O
that	O
virtual	O
reality	O
may	O
not	O
be	O
appropriate	O
for	O
people	O
who	O
are	O
in	O
ill	O
health	O
.	O
</s>
<s>
Mental	O
rotation	O
ability	O
:	O
Better	O
mental	O
rotation	O
ability	O
appears	O
to	O
reduce	O
susceptibility	O
to	O
virtual	B-Application
reality	I-Application
sickness	I-Application
,	O
suggesting	O
that	O
training	O
users	O
in	O
mental	O
rotation	O
may	O
reduce	O
the	O
incidence	O
of	O
virtual	B-Application
reality	I-Application
sickness	I-Application
.	O
</s>
<s>
While	O
the	O
relationship	O
between	O
field	O
dependence/independence	O
and	O
virtual	B-Application
reality	I-Application
sickness	I-Application
is	O
complex	O
,	O
it	O
appears	O
that	O
,	O
in	O
general	O
,	O
people	O
without	O
a	O
strong	O
tendency	O
towards	O
one	O
extreme	O
or	O
the	O
other	O
are	O
most	O
susceptible	O
to	O
virtual	B-Application
reality	I-Application
sickness	I-Application
.	O
</s>
<s>
Motion	O
sickness	O
sensitivity	O
:	O
Those	O
who	O
are	O
more	O
sensitive	O
to	O
motion	O
sickness	O
in	O
reality	O
are	O
also	O
more	O
sensitive	O
to	O
virtual	B-Application
reality	I-Application
sickness	I-Application
.	O
</s>
