Severe motion sickness is easily
identifiable with sufferers showing obvious
behavioral signs, including emesis (vomiting).
Mild motion sickness and sopite syndrome lack
such clear and objective behavioral markers. We
postulate that yawning may have the potential to
be used in operational settings as such a
marker. This study assesses the utility of
yawning as a behavioral marker for the
identification of soporific effects by
investigating the association between yawning
and mild motion sickness/sopite syndrome in a
controlled environment.
METHODS:
Using a randomized motion-counterbalanced
design, we collected yawning and motion sickness
data from 39 healthy individuals (34 men and 5
women, ages 27-59 yr) in static and motion
conditions. Each individual participated in two
1-h sessions. Each session consisted of six
10-min blocks. Subjects performed a multitasking
battery on a head mounted display while seated
on the moving platform. The occurrence and
severity of symptoms were assessed with the
Motion Sickness Assessment Questionnaire
(MSAQ).
RESULTS:
Yawning occurred predominantly in the motion
condition. All yawners in motion (N = 5) were
symptomatic. Compared to nonyawners (MSAQ
indices: Total = 14.0, Sopite = 15.0), subjects
who yawned in motion demonstrated increased
severity of motion sickness and soporific
symptoms (MSAQ indices: Total = 17.2, Sopite =
22.4), and reduced multitasking cognitive
performance (Composite score: nonyawners = 1348;
yawners = 1145).
DISCUSSION:
These results provide evidence that yawning
may be a viable behavioral marker to recognize
the onset of soporific effects and their
concomitant reduction in cognitive performance.
Sopite syndrome:
a sometimes sole manifestation of motion
sickness Graybiel A, Knepton J
Aviat Space Environ Med 1976 47;
8; 873-82
Severe motion sickness is easily identifi
able. People under signifi cant malaise stop
working, vomit or show signs of, such as pallor.
The problem is that mild motion sickness and
sopite syndrome do not demonstrate such clear
and observable behavioral markers. We postulate
that yawning may have the potential to be used
as such a marker. Yawning is an involuntary and
stereotyped behavior consisting of three phases,
a long inspiration phase, the mouth ' s wide
opening, and the fi nal slow expiration ( 2 ).
Yawning occurrence demonstrates an underlying
circadian rhythmicity ( 1 ), and has been
associated with sleepiness, drowsiness, and
boredom ( 2 ). Research supports the hypothesis
that yawning is associated with transitions in
arousal levels ( 1 ). It appears that yawning is
involved in maintenance of arousal, yet yawning
frequency seems to be unrelated to prior sleep
amount ( 1 ). Johnson and Jongkees [as cited
in Baenninger ( 1 )] suggested that yawning
may be associated with arousal by regulating
cerebral blood fl ow, and noted that the
deafmutes with congenitally incomplete
labyrinths are immune to yawning.
It has long been known that yawning is a
common symptom associated with motion sickness,
and is considered among the typical symptoms of
sopite syndrome ( 8 ). The term " sopite
syndrome " describes a symptom-complex centering
on drowsiness and lethargy related to motion
sickness ( 8 ). Symptoms associated with
drowsiness are yawning, disinterest and
disinclination to work, lack of participation in
group activities, mood changes, sleep
disturbances, and signs of mental
depression.
The literature on motion sickness does not
seem to contain any systematic efforts focusing
on yawning per se. In general, earlier research
does not extend beyond using yawning as one more
symptom toward assessing motion sickness
severity [for example, Bos et al. ( 3
)]. Furthermore, existing research is merely
based on postsession self-reports of yawning as
part of questionnaires reporting motion sickness
symptoms [for example, Joseph and Griffi n (
10 )].
Our study is triggered by the operational
consequences of soporifi c effects, which, we
hypothesize, can be even greater than the more
severe levels of motion sickness. The problem
with mild motion sickness and sopite syndrome is
that they are not easily distinguishable as
problems concerning the person ' s well-being or
their ability to perform assigned tasks. A mild
form of motion sickness includes an uneasy
feeling with a certain amount of lack of
interest in the task being done ( 14 ). This
phase is not characterized by any visible signs
and people may not be aware of their state ( 11
, 14 ). Therefore, a systematic approach to
soporifi c effects must include the
investigation of ways to identify this
phenomenon.
Developing measures can be the fi rst step
to countering the effect of sopite syndrome in
the operational environment ( 11 , 12 ). For
these reasons, this study has the objective to
investigate the utility of yawning as a
behavioral marker in the identifi cation of
soporifi c effects.
DISCUSSION
In this experiment, yawning was associated
with the existence of the nauseogenic motion
stimulus. Compared to non-yawners, individuals
who yawned in motion were more likely to suffer
from mild motion sickness and soporifi c
symptoms and they demonstrated reduced
multitasking cognitive performance. What makes
these results more interesting is the limited
severity of the nauseogenic motion.
Consequently, the average severity of motion
sickness in our study was mild. However, the
experimental methodology did not provide the
opportunity to evaluate the temporal
distribution of yawning versus soporifi c
symptoms, i.e., to assess whether yawning may be
considered as a prodromal response to sopite
syndrome or performance deterioration. The time
development of symptoms seemed to coincide with
performance deterioration because our method was
not focused on this assessment. This study has a
number of constraints that limit its external
validity. These caveats should be considered
when interpreting the generalizability of the
results. First, the number of yawning
individuals was small ( N 5 5). The second point
of concern is the method we used to identify
yawns, which was based on the researcher
observing and recording the yawns. Although this
approach is better than subject ' s self-reports
obtained after the data collection session, it
is an evaluation subject to the researcher ' s
bias and error in observations. Future efforts
should probably incorporate a 2-reseacher
approach ( 4 ).
A comment should also be focused on the
association between yawning and chronotype. Our
results suggest the confounding effect of
chronotype on yawning occurrence in nauseogenic
motion conditions. This fi nding is in
congruence with existing research showing that
yawning frequency is affected by differences in
sleepwake or sleepiness rhythms between extreme
chronotypes, with evening types yawning more
frequently during morning ( 15 ). Based on their
fi ndings, the researchers concluded that the
temporal distribution of yawning frequency
differs between chronotypes, supporting the
hypothesis that differences in sleep-wake rhythm
affect yawning. However, the small number of
yawning subjects in our study does not
constitute a solid base for our
chronotype-related results. Future efforts
should investigate further the interaction of
motion sickness and chronotype on the
development of yawning.
The difference in occurrence of yawns
between individuals with soporifi c and mild
motion sickness symptoms compared to
asymptomatic individuals under the same motion
conditions provides evidence that yawning may be
a viable behavioral marker of sopite syndrome.
The operational problem with mild motion
sickness and sopite syndrome is that both are
not easily distinguishable as problems because
they are not characterized by any visible signs,
with people not being aware of their actual
state. From an operational perspective, it would
be useful if yawning could serve as a behavioral
marker to recognize the onset of soporifi c
effects and their concomitant reduction in
cognitive performance.
This work is preliminary, based on a small
sample size, and leaves many questions
unanswered. A systematic investigation regarding
these issues is needed to further elucidate the
operational utility of yawning as a behavioral
marker for sopite syndrome.
