Students of behavior have neglected yawning.
It is rarely mentioned in animal behavior texts,
and even books that would seem to be
particularly relevant, such as Hinde's (1972)
Non Verbal Communication, do not include yawning
in the index. In physiology the standard texts
such as Starlings Human Physiology (Davson &
Eggleton, 1962) or the revised Johns Hopkins
Atlas of Human Functional Anatomy (1977) devote
only a few vague sentences to yawning, if it is
mentioned at all. There is no precise knowledge
of the eliciting stimuli, functions,
development, or topography of yawning. Darwin
(1873) described yawning in humans as an act of
deep inspiration, followed by a lengthy,
forceful expiration with simultaneous strong
contraction of many skeletal muscle groups, and
occasionally accompanied by lacrimation. Yawning
is sometimes described as a reflex, and
Moore (1942)
reported that yawning is one of the first
reflexes observed in newborn human infants.
Fatigue (Cramer, 1924; Mayer, 1921),
drowsiness and boredom (Barbizet,
1958; Provine
& Hamernik, 1986), hunger and satiety
(Barbizet, 1958) have all been suggested as
stimuli for yawning. A widely held hypothesis is
that oxygen insufficiency causes yawning, but
Starlings Human Physiology does not mention this
possibility, and Barbizet found the evidence for
it to be inconclusive. Frequent or excessive
yawning may accompany certain diseases of the
central nervous system, particularly frontal
lobe tumors and epidemic encephalitis, a
contagious inflammation of the brain (Brock
& Krieger, 1963). Gastric diseases, brain
stem lesions, and certain varieties of epilepsy
may also be accompanied by pathological yawning
(Barbizet, 1958). On the other hand, Geigel, a
Gerrnan physician, suggested that "a seriously
sick person does not yawn, and when he does yawn
again the danger is past" (cited by Cramer,
1924).
More recent research has indicated the
involvement of a central cholinergic mechanism
in the initiation of yawning by rats (Urba-Holmgren,
Gonzalez, & Holmgren, 1977), with a positive
modulating effect of serotonin (Urba-Holmgren,
Holmgren, Rodriguez, & Gonzalez, 1979). Low
doses of drugs that stimulate dopamine neurons
also induce yawning in rats (Mogilnicka
& Klimek, 1977). Injections into brain
or cerebrospinal fluid of ACTH,
melanocyte-stimulating hormone, or peptides
having similar hormonal activity induce a
stretching and yawning syndrome in several
species. There is an association between yawning
and some elements of sexual behavior (Houston,
1971), and Phoenix
and Chambers (1982) found that injections of
testosterone produced yawning by male and female
rhesus macaques. Holmgren, Urba-Holgrem,
Aguilar, and Rodriguez (1980) found that
testosterone treatment restored
cholinomimetically induced yawning in castrated
male rats and increased yawning in normal and
androgenized fernales.
Darwin (1873) noted that yawning occurred
aring displays of "passion" and threat in
baboons; rhesus macaque females have also been
observed to yawn during sexual excitement
(Dewsbury, 1978). Nonhuman primates yawn in a
variety of other contexts, and Hall (1962)
described a "gaping" or "yawning" response made
by captive patas monkeys, Erythrocebus palas,
when confronted with a mirror. He reported that
the response was similar to the yawning he had
observed in field studies of wild chacma baboons
and that Hinde and Rowell (1962) had observed in
captive rhesus macaques. Hall (1962, p1258)
reported that "the young female, in particular,
frequently made 'yawning' responses in which,
while staring towards the reflection, she
lowered the head while opening the mouth to
fullest extent, then raised the head again in
normal horizontal position. This reaction would
occur with the animal in the sitting, normal
standing, or lowcrouched postures.Calling such
behavior yawning is simply a useful description
because its functional variations and relations
to other behaviors have not been determined.
Herbivores have seldom been observed yawning
(Barbizet, 1958; Cramer, 1924; Heusner,
1946), but warm, well-fed, drowsy members of the
Felidae often yawn (Leyhausen, 1979), and
domestic Canids may yawn in certain social play
situations (Bekoff, 1974). Dumpert (1921)
asserted that yawning was universal in mammals
and birds, and Cramer (1924) reported that
amphibians and certain reptiles also yawn.
Although it is clear that members of these
classes may open their mouths widely on
occasion, it is not at all clear that they are
yawning when they do so.
In this report I describe observations of
yawning by a fish (Betta splendens), by a
carnivore (Panthera leo), and by two primate
species (Papio sphinx and Homo sapiens) in a
variety of settings. Because mere opening of the
mouth is not necessarily the saine as yawning,
in all of this research 1 defined yawning as a
slow opening of the mouth, maintenance of the
open position for more than 3 s, followed by a
more rapid closure of the mouth.
Siamese Fighting Fish (Betta
splendens)
While doing research on the aggressive
threats and other social behaviors of Betta
splendens (Baenninger,
1966; Baenninger, 1984), I observed yawning
during encounters with conspecifics and with
mirror images but not in their solitary
behavior. For this reason I hypothesized that
yawning would occur primarily when conspecifics
were visible, and particularly in aggressive,
intruder-resident interactions. Myrberg
(1972) described yawning of bicolor damselfish,
Eupomacentrus partitus, and discovered that it
accompanied transitions between various social
behaviors, particularly agonistic responses and
nest entrances and exits.
Experiments and Observations All fish
were purchased froin a commercial supplier and
were housed in Miter glass aquaria for 1 mo
before observations. They were observed from
behind a screen during the light-on phase of a
12-hr light cycle. They were fed a small amount
of frozen brine shrimp daily. Aquaria were
cleaned every 4 days. Yawning by 15 isolated
fish was observed for twenty 1-hr intervals in
the light-on portion of their daily light-dark
cycles. During these sessions the observer
viewed fish under 15-W white illumination
through holes cut in opaque material that
prevented fish from seeing the observer. Under
these circumstances only a single yawn was
observed. This constitutes a rate of 0.003
yawn/fish-hour. The frequency of yawning
increased greatly when 7 pairs of male Siamese
fighting fish were observed while separated by
clear Plexiglas partitions. Of the 14 fish, 12
yawned between one and seven times during a
single 1-hr observation that followed 24 hr of
visual isolation. There were 41 yawns during 14
fish-hours, a rate of 3.0 yawns/fish-hour. The
12 fish that yawned did so an average of 3.5
times per hour. There was no evidence of yawning
contagion in these observations; a
minute-by-minute analysis of responses did not
show any temporal pattern of yawns, either
between or within the protagonisis. That is, in
only one instance did members of a pair both
yawn during the saine or successive minutes, but
2 other fish were observed to yawn repeatedly
during successive minutes. These multiple yawns
were not reciprocated by the fish on the other
side of the transparent partition.
After these paired observations every fish
was again isolated for 24 hr, after which each
pair was again observed for 1 hr while separated
by clear Plexiglas. This time 3 (different) fish
failed to yawn, and 27 yawns were recorded, a
mean of 2.5 yawns for each fish thai yawned and
a rate of 1.9 yawns/fishhour. This decrease
between the first and the second observation was
significant by a sign test (p < .05,
two-tailed). If yawning were associated with
absence of stimulation or lack of stimulus
change, one might expect the rAponse to increase
after isolation and repeated exposure to the
saine conspecific. Instead, like the biting
response in repeated pair encounters of this
species (Baenninger, 1984), the pattern 1 am
referring to as yawning appears to wane.
The possibility of an association between
yawning and biting was studied in a third set of
observations. Novel pairs were formed by placing
5 individual male Bettas in the 12liter aquaria
of 5 resident males which had been living in
thern alone for 1 wk. The yawning and biting
responses of both residents and intruders were
counted during the first hour together; after 23
hr together, these responses were again counted
for 1 tir. During the first hour the two pairs
performed 153 bites and 60 yawns (6.0
yawns/fish-hour). After 24 hr there were 92
bites, but only 8 yawns (0.75 yawn/fish-hour).
In one pair the intruder was severely damaged by
the resident and showed neither biting nor
yawning responses. Putting pairs of fish
together was necessary in order to measure
biting, but because of the aggressiveness of
these fish toward conspecifics, this study was
run with a small number of subjects. It appears
that both biting and yawning responses wane with
continued exposure to the same conspecific and
that actual combat increases the initial yawning
rate, compared with the rate when fish have only
visual contact. In the final study, 14 pairs of
naive male fish, isolated in 1-liter aquaria,
were visually exposed Io each other. Their
yawning responses to a single conspecific in 1
hr were recorded. Fish were then isolated again,
but a mirror was placed against the aquaria of
seven pairs (14 fish) so that each subject could
view its own image instead of a conspecific; the
rernaining seven pairs saw neither mirrors nor
fish. Twenty-four hours later the yawning
responses to the original pair mernber were
again counted, This procedure was then repeated
after 48 hr. Under these circumstances, with the
mirror present for two 24-hr intervals, there
was only slight waning of yawning responses.
There were 55 yawns in response to pair members
during the initial hour (3.9/fish-hour), 64
after 24 hr of mirror viewing (4.6/fish-hour),
and 43 after a second 24-hr period of mirror
viewing (3. 1 /fish-hour). The no-mirror control
pairs essentially replicated the results of the
second study, by showing clear evidence of a
waning of yawns over repeated exposure to a
conspecific: Initially there were 65 yawns
(4.5/fishhour); 24 hr later there were 29 (2. 1
/fish-hour); and during the final pair
encouriter 48 hr later, there were 24 yawns
(1.7/ fish-hour). Having a mirror present during
isolation from conspecifics appears to
counteract the waning of yawning that normally
occurs in repeated pair encounters.
The rate of yawning by members of this
species is dramatically increased by the
presence of a single conspecific. There were 300
times as many yawns/hour when fish were in
visual contact with a conspecific. During actual
combat the rate of yawning was again doubled
initially, although it waned after prolonged
fighting, perhaps due to physical exhaustion.
Presence of a mirror while fish were isolated
prevented waning of yawns in visual pair
encounters that were separated by 24-hr
intervals. The possibility that yawning is an
aspect of agonistic threatening in this species
is clear, but it has not previously been
documented (Simpson, 1968).
Lions (Panthera leo)
Captive African lions were observed for 100
hr in an attempt to answer the following
questions: (a) Do lions (like humans) make
sounds, or stretch, when they yawn, and are they
more likely to yawn in some postures than in
others? (b) Do lions yawn at high frequencies,
and are there particular environmental events
that modify those frequencies? (c) Docs
contagion of yawning occur among members of this
species? (d) Is there any evidence for contagion
of yawning between lions and people?
Method : Observations of yawning were
conducted for 100 hr at the Philadelphia Zoo in
the lion bouse from July 21, 1982, to March 25,
1983. The house contained 5 lions, 3 females and
2 males. Each animal had its own tiled cage, but
except at feeding time (3:00 p.m.) 4 of the
lion3 were kept in pairs. The observer sat on a
wooden bleacher located 10 m from the cages so
that all 5 lions could be seen simultaneously.
Behavior was scan-sampled for one bundred 1-hr
periods at différent times from 9:00 a.m.
to 5:00 p.m. Temperature, time, and the
incidence of yawning were recorded, as was the
time between yawns (an interyawn interval of 20
s was established as an arbitrary criterion for
contagion). The approximate number of people
entering the lion house during the hour and the
number of people in front of a lion's cage when
it yawned were recorded in order to determine
whether yawning frequency was correlated with
the number of human observers present. A lion's
position when it yawned was recorded (standing,
sitting, or lying down), as was the occurrence
of stretching or making a sound during
yawns.
Results : During 100 hr of
observation, the 5 lions yawned 592 times, a
rate of 1.2 yawns/lion-hour. No relation was
found between the number of yawns per hour and
the mean number of people entering the lion
house per hour (r = .14), nor was any relation
found between the number of yawns per hour and
the number of people standing in front of the
cage when a yawn occurred (r = .09). The time of
day was related to the frequency of yawning,
however. During the morning there were
relatively few yawns (0.8/lion-hour), but there
was a progressive increase before feeding tirne
(to 1.8 yawns/lionhour between 1:00 and 2:00
p.m.). During and after feeding there was a
sharp decline in the frequency of yawns (0.35
yawn/lion-hour).
Of a total of 592 yawns, only 19 (3.1 %)
occurred within 20 s of another yawn. No
instances of multiple yawns by the same
individual were seen. Only 4.5% of the yawns
were accompanied by a stretch, and sounds were
never detected during yawns. Lions yawn most
often when they are lying down. Of 592 yawns,
435 occurred when the lion was lying down; 122
occurred while the animal was standing, and 35
occurred while sitting (with only rear quarters
contacting the floor). In the winter months the
temperature was kept Illween 70 and 75*F, but in
the summer the temperatures in tl* lion house
climbed past 80*F, and the highest temperature
recorded was 85'F. Yawning was most frequent
when the temperature was between 70 and 74
(corrected for the number of observations in
that temperature range) and declined when the
temperature fell below or rose above this range.
Yawning by lions occurred most often just before
feeding, when they presumably are hungry, and
when room temperature is warin, but not hot. It
was not contagious, and the presence of large
numbers of humans did not affect the frequency
of yawns by lions. They yawned most often while
lying down.
Mandrills (Papio sphinx)
The open-mouthed aggressive threat is a
common behavior in a number of primate species.
To what extent is this response discriminable
from yawning, and does its frequency covary with
yawning? Are there reliable variations in
yawning frequency over the course of a day? Is
there any evidence of social facilitation or
contagion of yawning in this species of Old
World monkey?
Method : Mandrills were observed in
the rare marnmal house of the Philadelphia Zoo
during March and April of 1983 and in March and
April of 1985. Two females were housed with one
male, and a younger male had a private cage but
could see his conspecifics. The animals were
enclosed in tiled, soundproof glass cages. At
feeding time (3:00 p.m.) males ate in separate
cages, and the fernales ate together in one
cage. To make observations, the observer stood
about 2 m from the cages and observed for 1-hr
intervais during different times of the morning
and afternoon. Time, temperature, and the number
of yawns performed during each hour were
recorded as well as whether yawns occurred
within 20 s of each other. The number of people
standing in front of a cage when yawning
occurred was recorded, as was the approximate
number of people who entered the rare mammal
house during an observation period. Positions of
mandrills while yawning and whether they
stretched during yawns were recorded as well as
the sex of the yawner.
Results : Two different types of yawns
occurred in the males. In one type the animal
raised its head and opened its mouth so widely
that its teeth were exposed, particularly the
large canines that are characteristic of males.
This response lasted 4-5 s and was never seen in
females. In the second type of yawn, the head
was raised only slightly, and the mouth did not
open widely enough to expose the teeth, which
remained covered by the lips. This response
lasted only 1-2 s and was shown by both sexes.
Only these shorter duration responses were
scored as yawns. It appears likely that these
were true yawns, whereas the longer duration
response was really a "bared-teeth display"
shown exclusively by males in primate species
during hostile encouriters. Yawning was never
observed just before or after sleep episodes,
and only 8% of the yawns occurred while the
animal was lying down. The remaining 92%
occurred while animals were in a sitting
posture, but yawning was never obsmed while an
animal was standing.
During 36 hr of observation, there were 111
yawns by the 4 mandrills, a rate of 0.78
yawn/mandrill-hour. There was no significant
correlation between the number of yawns per hour
and the number of people in the rare mammal
house (r = .26), nor was there a correlation of
yawns per hour with the number of people in
front of the cage when yawns occurred (r = .17).
Ambient temperature did not vary as much as in
the lion house and was uncorrelated with rate of
yawning by mandrills. There was a clear relation
between the number of yawns per hour and the
time of day. One hour before the animals were
fed, there was an increase in yawning frequency,
from a mean of 1.5 yawns/mandrill-hour between
1:00 and 2:00 p.m. to 6.5 between 2:00 and 3:00
p.m. After feeding, the frequency again
decreased to 2.0; all animals finished feeding
by 3:30 p.m. Yawning contagion was not apparent
(by a 20-s criterion for the interval between
yawns by différent individuals). Multiple
yawns by individuals were noted, that is, when a
mandrill yawned, it occasionally repeated the
response within a few minutes. The two
mouth-opening responses (the bared-teeth
displays and the true yawns) bore no temporal or
sequential relation to each other.
Discussion of Fish, Lions, and
Mandrills
Visual contact with conspecifics or mirror
images appears to be necessary for yawning to
occur it all in Siamese fighting fish, and the
highest rate of yawning occurs when visual,
tactile, and chernical contact are possible
among fish. As with aggressive biting, the
response habituates with prolonged visual or
physical contact. In the two mammal species,
individuals had presumably habituated to one
another through prolonged contact and
familiarity. The male mandrills occasion ally
showed a bared-teeth display to each other,
presumably as a threat, but no such aggressive
displays were observed in the lions. Siamese
fighting fish in the laboratory yawned
exclusively in social settings, so the response
is probably also an aspect of aggressive
displays in this species.
The clearest result of the zoo observations
was the increase in yawning just prior to
feeding time which occurred in both lions and
mandrills. Feeding may well be the major event
of the day for zoo animals (aside from cage
cleaning and randomly occurring social
interactions), so this finding appears contrary
to the belief that yawning is associated with
lack of stimulation. As with the fish, the
anticipation of major stimulus events may be
associated with an increase in yawning by lions
and mandrills. Another possibility is that
lions, mandrills, and fighting fish all yawn in
anticipation of metabolically expensive events
such as feeding or fighting. Increased oxygen
consumption and metabolic rate characterize such
behaviors, but increasing respiration rate might
accomplish the saine adaptive outcome.
Humans (Homo sapiens)
Data on yawning frequency by people were
collected in several différent publie
situations. The procedures used in each of these
operant level determinations are described
together with the results from each sampling
situation. The frequency of yawning by riders on
Philadelphia's Broad Street subway line was
observed in a series of observations lasting
from 10 to 30 min. The number of people present
was estimated, and an attempt was made to record
every yawn by sitting at one end of the subway
car and facing the other riders. A scan-sampling
method was used, with a 10-s period taken for
each end-to-end scan of the car (Altmann, 1974),
but yawns were always recorded if they were
noticed. Most of the observations were made
between 7:30 and 9:30 a.m. and between 5:30 and
8:00 p.m. As expected, yawning was a relatively
low-frequency event. The duration of each
observation period was multiplied by the
estimated average number of people present
during the observation, and the resulting
product (person-hours) was the denominator in
assessing the relative frequency of yawning. In
a total of 12,130 person-hours of subway
observation, only 95 clear yawns were recorded.
Sixty-five of the yawns occurred during morning
observations, when 12,067 person-hours were
observed; 30 of the yawns occurred after noon
during the remaining 64 person-hours of
observation. Thus, the relative frequency of
yawning was much greater during the afternoon
and evening observations (about 0.48
yawn/person-hour versus 0.0054 in the
morning).
The relative frequency of yawning was much
greater when fewer people were present (less
than 15). Ten yawns occurred during the 44
person-hours when fewer than 15 riders were in
the subway car (about 0.24 yawn/person-hour); 85
yawns were made during the 12,086 person-hours
in which more than 15 riders were present (about
0.006 yawn/person-hour). During 30-min
observations at lunch and dinner in dormitory
cafeterias of Temple University, the observer
recorded yawning at large tables where 7-22
other students were also eating lunch or dinner.
During 43.5 hr of observation, spread over 2 mo,
there were only four yawns observed-two at lunch
and two at dinner (approximately 0.009
yawn/personhour). Yawning while eating at
communal dining tables appears to be an
infrequent event. Five 45-min aerobics classes
comprising 15 students produced a total of four
yawns, an average yawn frequency of 0.00 12
yawn/person-hour, one of the lowest recorded in
any situation observed. Intense, rhythmic
physical exertion does not appear to be
associated with frequent yawning. Whether this
is due to direct inhibition by exercise or to
concentration on another activity is presently
unknown.
Leisure activities in dormitories were
associated with higher yawning rates than was
eating or aerobics. While students were watching
TV, conversing casually, or drinking beer in
groups of three or more, the student observer
counted 92 yawns during 5 tir. With a mean of
five students in the group, this produced a
frequency of 3.6 yawns/person-hour. Seventeen
meetings of a mathematics class (calculus) were
observed by a student observer for 40-min
periods in the middle of the class meeting. A
total of 248 yawns occurred during these
observations, a rate of 24.6 yawns/person-hour.
This was the highest rate of yawning obtained in
any of these observations. Finally, yawning was
observed in the campus library on 25 occasions
during the middIe of the semester. Recording was
limited to the five tables adjacent to the
observer's position, and sessions lasted for 20
min. A mean of 8 students were present at the
tables being observed. Fifty-nine yawns occurred
under these circumstances, a frequency of
approximately 0.9 yawn/person-hour.
Laboralory Experiment : Having
collected data on the operant level of human
yawning in a variety of situations, a laboratory
manipulation of yawning frequency was attempted.
One of the phenomena associated with yawning is
its contagiousness. Moore (1942) found that
people in college libraries and church services
yawned in response to the sight of someone
yawning; Moore also found that audio recordings
and motion pictures induced yawning in
experimental subjects. Responses to the auditory
stimulus were counted objectively, but subjects
reported on their own yawns to the visual
stimulus. No attempt was made to disguise the
purpose of the stimulus presentations, so that
suggestible people may well have yawned in
response to perceived demand characteristics of
the situation rather than because of contagion
per se. In a recent study by Provine (1986),
subjects yawned in response to being asked to
think about yawning. On the basis of his
findings, Provine suggested that yawning may be
triggered by still unspecified physiological
events or released by witnessing yawns or
"yawn-related stimuli." Presumably, recording
their own yawns contributed to his subjects'
thinking about yawning.
Method : Forty undergraduate
psychology students served as subjects. In my
laboratory a semiprofessional actor read a
passage from Alice in Wonderiand (the mock
turtle's story) either live or on a videotape to
the students, who were either alone or in pairs.
After either one quarter or three quarters of
the 7-min reading, the actor paused and yawned
audibly, without covering lier mouth. If fatigue
or boredom elicited yawning, then more yawns
should occur later in the reading, and yawns
elicited by seeing the actor yawn should occur
in equal numbers after cither interval.
Following the reading, in which yawns were
recorded by the experimenter, subjects were
asked to recall all facial expressions portrayed
by the actor and to judge how well they were
portrayed. Subjects were also asked how long
since they had caten and slept, what sort of
mood they were in, whether they yawned or felt
like yawning during the reading, and whether
they were aware of the reader's yawn.
Results : Only three yawns were
elicited during the entire experinient, two in
the video condition and one with the live actor;
all three were in subjects who were alone. Two
occurred within 20 s of the stimulus yawn, and
one occurred 3 min later. All three yawns
occurred during the last quarter of the reading.
These data provide little evidence for the
contagiousness of yawning. Most subjects (82%)
reported that they were aware of the reader's
yawn, and 46% reported that they felt like
yawning, although only 3 did so. One yawner had
not slept for 14 hr, but the other 2 had slept
recently. For the experiment overall, the rate
of yawning in the laboratory was O~ 15
yawn/person-hour.
General Discussion
Visual contact with conspecifics or mirror
images appears to be necessary for yawning in
Siarnese fighting fish, but enforced physical
contact resulted in the highest rates of
yawning. This procedure was accompanied by
aggressive interactions, and it appears that
yawning is a type of social response in this
species. Like aggressive biting, yawning wanes
with prolonged contact of individuals unless
mirrors are present. In the two marnmal species
observed in captivity, individuals had
presumably habituated to one another, so that
the absence of social yawning in these species
may have resulted front the familiarity of
individuals with one another. Yawning niay be a
response to interesting stimuli in these three
unrelated vertebrates: The fish yawned most in
the presence of novel conspecifics, whereas both
lions and mandrills yawned most frequently prior
to feeding, when they were attentive to the
imminent appearance of a caretaker bringing
food.
By contrast, the rate of yawning in humans
increased when few people were present, when
social, physical, or cognitive stimulation was
lacking. High rates of yawning were associated
with relatively emply subway cars late in the
day, with leisure-time dormitory activities
(primarily TV walching and desultory
conversation), with lecture classes, and with
library studying. The lowest rates of yawning
observed outside the laboratory occurred in
crowded subway cars during morning rush hours,
in crowded, communal dining halls where students
were conversing, and in aerobic exercise
classes. The possibility thus exists that
yawning in humans differs functionally from
apparently similar responses observed in other
vertebrate species. These data indicate that a
scarcity of both conspecifics and interesting
stimuli may promote yawns in our species, as
shown by Provine ( 1986), whereas the presence
of conspecifics and interesting stimuli were
associated with yawning in the three other
species observed.
Simply feeling bored, as many subjects
undoubtedly did while having Alice in Wonderland
read to them, was not sufficient to elicit
yawning in this experiment. The failure to
elicit yawning in the laboratory, associated
with the fact that nearly half of the subjects
reported feeling like yawning, suggests that
anxiety from being under observation may have
inhibited any yawning; that would otherwise have
occurred. Students participating in experiments
are often somewhat anxious, eager to please, and
concerned about the impression they make on the
experimenter. Future laboratory studies, in
which yawning frequencies are objectively
recorded by an observer, are needed to assess
the possible effects of such social anxiety on
human subjects. The present data are
insufficient to establish such effects.
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
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