It is commonly believed that yawning is
caused by boredom, lack of oxygen, and seeing
other persons yawn. Such an oddly disparate set
of antecedent stimuli might seem to, make
yawning a focus of interest for those who study
biosocial aspects of behavior. But this has not
been the case, and relatively few psychologists
have studied yawning. As a result we are still
uncertain about the precise circumstances under
which these common beliefs about yawning are
true (or not true). Provine, Tate, and
Geldmacher (1987) found that changes in oxygen
and carbon dioxide levels did not affect yawning
frequency, whereas Provine and Hamernik (1986)
found that concentration on boring stimuli, such
as TV test patterns, did increase yawning
frequency.
A comparably diverse set of neuroendocrine
pathways has been found to regulate yawning.
Neurotransmitters such as dopamine (Yamada,
Nagashima, Kimura, Matsumoto, & Furukawa,
1990), acetylcholine (Cowan, 1978;
Urba-Holmgren, Gonzalez, & Holmgren, 1977),
and serotonin (Urba-Holmgren, Holmgren, &
Gonzalez, 1979) have been implicated, as well as
steroid hormones such as estrogen and
testosterone (Phoenix & Chambers, 1982),
oxytocin (Argiolas, Melis, Stancamp, &
Gessa, 1990), and ACTH or adrenocorticotrophic
hormone (Argiolas, Melis, & Gessa, 1988).
Yawning has been found in all the major
vertebrate classes, including several mammalian
orders (e.g., primates, carnivores, and
rodents), fish (Baenninger, 1987), birds
(Dumpert, 1921), reptiles (Barthalmus &
Zielinski, 1988), and amphibians (Cramer, 1924).
Thus, the evolution and physiological correlates
of yawning both present intriguing questions. In
itself, the fact that so many apparent
mechanisms are associated with yawning, in so
many different species, suggests that the act is
of some general importance.
In primates yawning may have evolved as a
form of nonverbal communication. Deputte (cited
by Redican, 1982) found that yawning was
contagious among individual nonhuman primates of
similar age and social status. He interpreted
this contagion as an adaptive means for
synchronizing activities (especially the
sleep/waking cycles) of the individuals in a
mobile troop of primates. One implication of
this view is that troop leaders would likely
initiate more yawning than subordinates, and
Hadidian (1980) found that this was the case.
Males also yawn more than females among nonhuman
primates, although not in humans (Schino &
Aureli, 1989). Dominant males may simply be
making more threat displays that involve mouth
opening, although Phoenix and Chambers (1982)
found that testosterone injections increased
yawning frequency by both male and female rhesus
macaques. Sauer and Sauer (1967) proposed that
yawning induces relaxation of social tension in
groups. This would account for yawning
contagion, but does not explain why nonsocial
animals would yawn, or why social animals, such
as humans, yawn when they are alone.
In humans yawning also has a social contagion
aspect. Moore (1942) reported that people in
college libraries and church services yawned in
response to seeing a trained actor yawn. But
Moore's observations were rather poorly
controlled and have proved difficult to
replicate within the confines of the laboratory.
In our laboratory we have consistently failed to
find contagion of yawning when human subjects
are being openly observed; in one study an actor
yawned during a reading delivered in person or
via TV and there were virtually no yawns in
response by 40 laboratory subjects (Baenninger,
1987).
In the studies reported here we have
attempted to increase the frequency of solitary
human yawning as a way of gaining stimulus
control over the act; the relatively low
baseline frequency of yawning is, of course, a
stumbling block for research. In these studies
we have also begun to examine some physiological
correlates of yawning as a way of trying to
understand what bodily functions it may serve.
[......]
General Discussion
If yawning is a form of nonverbal
communication among humans then its inhibition
appears to be under voluntary (or
quasi-voluntary) control. The consistent finding
in these three studies was that people did not
yawn when they believed that they were being
observed by laboratory scientists/faculty. In
Experiment 1 yawning occurred while subjects
were reading about it, but only when the
observer appeared to be a student who was not
observing them; in Experiments 2 and 3 an
apparently relaxing setting was not associated
with increased yawning, presumably because
subjects did not perceive it as relaxing. It is
possible that subjects failed to yawn because
they had no desire to communicate nonverbally
with anyone, but it seems more likely that
subjects were experiencing a certain amount of
anxiety in the laboratory, either because they
believed that their performance was somehow
being observed and evaluated, or because they
all subscribed to the social convention that
yawning in public is impolite and is an act that
should not be performed in the presence of
authority figures. Such personal constraints
increase the difficulty of performing objective
studies of yawning, but we have recently found
that self-reports by subjects are in close
agreement with videotaped records, when the
camera was hidden (Greco & Baenninger,
1989).
In these studies a reliable physiological
correlate of spontaneous yawning was found, in
the form of a drop in skin conductance
immediately following yawns. When students were
asked to produce yawns these nonspontaneous
"faked" yawns were not reliably accompanied by
this change. Changes in skin conductance are
commonly used as one measure of sympathetic, or
visceral, arousal level; the implication seems
clear that yawning may thus affect this form of
arousal. The possibility that this effect is a
major function of most yawning acts is the
working hypothesis of our ongoing research
efforts.
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
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