Yawning is a very obvious act in humans
and other animals, yet it has not received much
attention in either science or daily life. In a
recent review of "evolution and facial action in
reflex, social motive and paralanguage" yawning
received no mention (Fridlund, 1991). To some
extent, this lack of interest may be because
yawning is rarely life-threatening; in fact,
frequent or excessive yawning does accompany a
wide range of pathological conditions, including
frontal lobe tumors, epidemic encephalitis,
supranuclear palsy, certain gastric diseases,
brain stem lesions, some forms of epilepsy,
motion sickness, narcotic withdrawal, and chorea
(Barbizet, 1958; Comroe, 1974; Graybiel &
Knepton, 1976; Heusner, 1946; O'Brien, 1976;
Rudolph, Barnett, & Einhorn, 1977).
Yawning has been observed in individuals
belonging to all classes of vertebrates
(Baenninger, 1987; Craemer, 1924) and is one of
the very earliest acts that human infants
perform (Blanton, 1917). It has been observed in
rat fetuses at 20 days (Smotherman &
Robinson, 1987). In 1955 Ferrari, Floris, and
Paulesu discovered that a yawning-stretching
syndrome was elicited in laboratory dogs 30 min
after intracerebroventricular injection of ACTH.
Subsequent research on pharmacological induction
of yawning has suggested that yawning
elicitation results from an interaction between
inhibitory dopaminergic and excitatory
cholinergic influences on a specific motor
program, possibly in the brain stem
(Urba-Holmgren et al., 1990).
Androgenic influences on yawning have been
found. Goy and Resko (1972) showed that
testosterone injections produce both yawning and
penile erections in male rhesus monkeys; Phoenix
and Chambers (1982) found that testosterone
propionate, but not estradiol, produced yawning
in females and pseudohermaphrodites, as well as
in males. In nonhuman primates males yawn
significantly more than females; this is not
true in humans (Schino & Aureli, 1989).
Yawning thus appears widespread
phylogenetically, very early ontogenetically,
and is subject to a variety of peptide and
steroid influences. All of this suggests that it
must be an important act, but its functions in
our species have remained elusive.
One approach to inferring the functions of a
behavioral act is to determine the context in
which it occurs, including its antecedents and
consequences (Baenninger & Greco, 1991). One
of the practical difficulties in studying
low-frequency behavioral acts such as yawning is
that observers must be very patient; long
periods of time may elapse between performances
of the act by an individual. Observing groups of
people in different situations gives some
information; for example, Baenninger (1987)
reported data on rates of yawning in lecture
classes, subway cars, cafeterias, and so forth.
But information on antecedents and consequences
of yawning for individuals is not available in
such a procedure.
Asking individuals to keep tallies of their
own yawning is one approach to solving this
problem. Despite our initial reservations about
the subjective nature of such personal data, the
procedure has been shown to be a valid measure
in the laboratory, at least for short time
periods (Greco & Baenninger, 1989). Keeping
a log specifically for any behavioral act may
artificially increase the frequency with which
that act is reported, because the attention of
log-keepers is more than usually focused on the
act. At present we can offer no solution for
this potential artifact. In the first part of
this report we present data from "yawn logs"
kept by volunteer subjects over the course of 1
week.
Another solution to the problem of gathering
data is to survey individuals about when they
yawn. Whether respondents can report accurately
the situations and times of day at which they
actually do yawn is, of course, an empirical
question. In such a survey, people may report
when they think their yawning occurs, but the
data may reflect beliefs and common sense"
rather than actual fact. In the second part of
this report we present results of a survey of
yawning that we carried out. By comparing such
survey data with personal logs kept by
individuals we may reach more valid conclusions
about the circumstances under which yawning
occurs.
[....] GENERAL
DISCUSSION
Although there were areas of agreement
between the two studies some discrepancies
emerged that may reflect differences between
keeping a log and responding to a survey: The
former represents what subjects actually do, and
the latter represents what they believe they do.
For example, the log data indicated no
relationship between sleep duration and yawning
frequency during the following day; survey
results indicated that respondents believe that
there is a relationship.
Survey respondents believed that they yawn
more in the afternoon than in either the morning
or evening, but the log results flatly
contradict this belief because afternoon hours
were when the percentages of daily yawns fell to
their lowest levels. Survey respondents believed
that lying in bed at night and arising in the
morning were both situations where yawning was
frequent. Partly supporting this finding, the
logs in Study 1 showed that the first hour after
waking and the last hour before bed were the
times when most yawns occurred, although the
logs indicated that it is the activities that
accompany retiring to bed and arising in the
morning that are associated with yawning. In any
event, this temporal variation supports findings
of Provine, Hamernik, and Curchak (1987) in
humans and of Anias, Holmgren, Urba-Holmgren,
and Eguibar (1984) in rats. In rats of a strain
selectively bred for a high frequency of yawning
(Urba-Holmgren et al., 1990) a clear circadian
variation of yawns existed, with a peak
frequency in late light and early dark hours
(Anias et al., 1984).
Frequent yawning thus appeared to be
associated with the transition between different
levels of arousal; the log data on actual
yawning show that the first hour and the last
hour of the waking day are the peaks of yawning
frequency. Except for these peaks, mornings and
evenings were not periods during which yawning
frequency was unusually high however. Relatively
few yawns are actually performed during the
afternoon, a period when adults do not normally
shift from activity to inactivity or vice versa.
Apparently the yawns that were emitted in the
early and late afternoon were primarily
associated with driving.
If yawning is somehow related to level of
arousal (Askenasy, 1989; Greco & Baenninger,
1991) one would expect yawns to occur frequently
when transitions between different levels of
arousal are required, as when people are first
getting up in the morning, when they are
retiring for the night. A less obvious
prediction from this arousal hypothesis is that
people should yawn frequently while attending
lectures, and when driving a car (both
activities in which keen attention and easy
relaxation are likely to alternate). This was
what we found.
For experienced drivers driving is a relaxed
activity for which a certain level of arousal
(or at least attention) is needed occasionally.
Our log data indicated that driving a car late
at night was associated with yawning; survey
respondents agreed, and also believed that they
were unlikely to yawn while driving on a sunny
day with no traffic, or while sitting in
traffic. The driving conditions under which logs
showed yawning were unfortunately not specified
exactly; the majority were commuting to school,
but whether they were mainly at speed or stopped
in traff ic could not be determined.
Like driving, listening to lectures is an
activity in which arousal levels may frequently
shift between alert attention and a relaxed
state that may border on sleeping. In both
studies listening to lectures was the most
frequent situation associated with yawning. Over
21% of the yawns were reported in the logs
during this activity; informally, college
students reported to us that they spend about 3
hr (18% of the day) in lecture classes. Survey
respondents overwhelmingly (75%) believed that
they were likely to yawn during lectures. This
result agrees with an earlier finding that the
rate of yawning was higher during lecture
classes than while eating, talking, watching TV,
riding in the subway, or virtually any other
activity observed (Baenninger, 1987). The belief
by survey respondents that they yawn most
frequently in lectures appears to be
correct.
Data on yawning of other vertebrate species
have rarely been reported systematically
(Baenninger, 1987), but the few studies where
yawning has been mentioned support the
hypothesis that transitions in arousal level may
be associated with frequent yawning. Myrberg
(1972) found that damselfish Eupomacentrus
partitus yawned when making transitions between
various social behaviors such as agonistic
responses and nest entrances/exits, a finding
confirmed by Baenninger (Il 987) in Siamese
fighting fish, Betta spiendens. Among members of
the Felidae (Baenninger, 1987), Canidae (Bekoff,
1974), and nonhuman primates (Baenninger, 1987;
Hall, 1962; Hinde & Rowell, 1962),
transitions between behavioral states (such as
anticipation of feeding or play) also appear to
be accompanied by yawns. In laboratory rats
Holmgren et al. (1991) have reported a
food-anticipatory yawning rythmn.
Survey respondents reported that they were
likely to yawn when tired or sleep-deprived. Our
data from the yawning logs did not support this
belief; the lack of any correlation between yawn
frequency and hours of sleep during the previous
night suggests that this widely held belief is
incorrect, at least for our college student
subjects (whose sleeping patterns may not be
typical of the general population).
Performance of activities that were observed
or judged by others was believed by the survey
respondents to make yawning unlikely (e.g.,
being interviewed, giving a speech, or waiting
for a competition to begin). The subjects who
kept logs did not report any of these public or
competitive activities, so we cannot make any
clear comparisons. In a general way the log data
do confirm these survey results, because
relatively few yawns occurred while the
log-keepers were working and talking.
Unless they actually keep track of the
circumstances under which they yawn, most people
probably are not normally aware of their own
yawns and are unlikely to recall much about
them. When asked, as in our survey, to recall
anything about their own yawning they are likely
to rely on widely held beliefs or "common sense"
rather than on empirical observations of
themselves. These beliefs may bear only a
marginal relationship to the actual distribution
of yawning frequency assessed by keeping logs.
This suggests that people may not normally pay
much attention to yawning; like breathing,
blinking, sighing, and other biologically
important acts, yawning is taken for granted and
ignored unless it is disrupted or abnormal in
some way. Until fairly recently, this lack of
attention has also characterized scientific
interest in yawning.
voir aussi
- Baenninger R,
Binkley S, Baenninger M Field
observations of yawning and activity in
humans.
- Baenninger
R On yawning and its functions
- Baenninger
R, Greco M Some antecedents and
consequences of yawning
- Greco
M, Baenninger R On the context of
yawning: when, where, and why ?
- Baenninger R
Some comparative aspects of yawning in
Betta sleepnes, Homo Sapiens, Pantera leo and
Papio sphinx
- Greco M ,
Baenninger R Effects of yawning and
related actvities on skin conductance and
heart rate
- Is
yawning an arousal defense reflex ?
Askenasy JJ
