- Tous
les articles sur la contagion du
bâillement
- All
articles about contagious
yawning
Yawning is a primitive and stereotyped motor
action involving orofacial, laryngeal,
pharyngeal, thoracic and abdominal muscles.
Contagious yawning, an involuntarily action
induced by viewing or listening to others'
yawns, has been demonstrated in human and
several non-human species. Previous studies with
humans showed that infants and preschool
children, socially separated during video
experiments, were not infected by others' yawns.
Here, the authors tested the occurrence of yawn
contagion in 129 preschool children (ranging
from 2.5 to 5.5 years) belonging to five
different classes by video recording them in
their classrooms during the ordinary school
activi- ties. As it occurs in adult humans,
children of all ages were infected by others'
yawns within the 2 min after the perception of
the stimulus. The yawn contagion occurred
earlier than previously thought. For children,
it appears that the natural social set- ting is
more conducive to yawn contagion than the
inherently artificial experimental approach.
Moreover, children's gender did not affect the
level of contagious yawn- ing. The neural,
emotional and behavioural traits of preschool
children are probably not sufficiently mature to
express variability between boys and girls;
nevertheless, children appeared to be already
well equipped with the 'neural toolkit'
necessary for expressing yawn contagion.
Le bâillement est une action motrice
primitive et stéréotypée
impliquant les muscles orofaciaux,
laryngés, pharyngés, thoraciques
et abdominaux. Le bâillement contagieux,
une action involontaire induite par
l'observation ou l'écoute des
bâillements d'autrui, a été
démontré chez l'homme et plusieurs
espèces non humaines. Des études
antérieures chez les humains ont
montré que les nourrissons et les enfants
d'âge préscolaire,
séparés socialement lors
d'expériences vidéo,
n'étaient pas réceptifs aux
bâillements des autres. Ici, les auteurs
ont testé la survenue de contagion du
bâillement chez 129 enfants d'âge
préscolaire (de 2,5 à 5,5 ans)
appartenant à cinq classes
différentes en les enregistrant dans
leurs salles de classe pendant les
activités scolaires ordinaires. Comme
cela se produit chez les adultes, les enfants de
tous âges ont été
réceptifs aux bâillements des
autres dans les 2 minutes suivant la perception
du stimulus. La contagion du bâillement
s'est produite plus précocément
que prévu. Pour les enfants, il
apparaît que le cadre social naturel est
plus propice à la contagion du
bâillement que l'approche
expérimentale intrinsèquement
artificielle. De plus, le sexe des enfants
n'affectait pas le niveau de contagion. Les
traits neuraux, émotionnels et
comportementaux des enfants d'âge
préscolaire ne sont probablement pas
suffisamment mûrs pour exprimer la
variabilité entre garçons et
filles; néanmoins, les enfants semblaient
déjà bien équipés de
la «boîte à outils
neuronale» nécessaire pour exprimer
la contagion du bâillement.
- Introduction
- "Imagine a yawn. You stretch your jaws open
in a wide gape, take a deep inward breath,
followed by a shorter exhalation, and end by
closing your jaws...You have just joined
vertebrates everywhere in one of the animal
kingdom's most ancient rites" (Provine, 2005 p.
532).
-
- Yawning is a primitive and complex
stereotyped motor response that requires the
involvement of facial, oral, laryngeal,
pharyngeal, thoracic and abdominal muscles
(Provine, 2005). Among vertebrates, spontaneous
yawning is a ubiquitous and evolutionarily
conserved behaviour (Provine, 2005; Walusinski
& Deputte, 2004). This activity
- seems to serve important neurophysiological
functions such as brain cooling and enhancement
of blood flow to the skull, which, in turn,
could stimulate cortical arousal and state
change (for an extensive re- view see Massen
& Gallup, 2017).
-
- Spontaneous yawning is driven by
physiological stimuli, it is widespread
throughout the animal kingdom and it follows a
daily fluctuation (Giganti & Zilli, 2011;
Massen & Gallup, 2017). On the other hand,
contagious yawning, an involuntarily action
induced by viewing or listening to others' yawns
(Provine, 2005), is socially driven and must
follow a different 'pathway' compared to
spontaneous yawning.
-
- Indeed, contagious yawning shows some
differences in daily fluctuation (Giganti &
Zilli, 2011) and it is not widespread across
different animal species; even, this phenomenon
occurs in some but not all species belonging to
the same family. For example, within the hominid
family, yawn contagion has been shown in
chimpanzees (Campbell & Cox, 2019; Campbell
& de Waal, 2011), bonobos (Palagi et al.,
2014) and humans (Provine, 2005) but not in
gorillas (Palagi et al., 2019), thus suggesting
that phylogenetic closeness cannot necessarily
predict, per se, yawn contagion (Palagi et al.,
2020). Outside the primate order, evidence of
contagious yawning are reported for dogs and
wolves (Neilands et al., 2020; Romero et al.,
2013, 2014; Silva et al., 2012), Asian and
African elephants (Rossman et al., 2017; Rossman
et al., 2020), sheep (Yonezawa et al., 2017),
elephant seals (Wojczulanis-Jakubas et al.,
2019) and parrots (Gallup et al., 2015; Miller
et al., 2012). The occurrence of yawn contagion
may be linked to the level of attention and
responsiveness to conspecifics' stimuli. Studies
car- ried out on humans showed a positive
association between the prolonged duration in
attentively fixing the eye region of fellows and
the increase in the detection sensitivity to
others' expressions including yawning (Bal et
al., 2010; Chan & Tseng, 2017). In this
view, in highly social species (e.g., wolves,
chimpanzees, bonobos), the higher levels of
affinitive interactions can promote the access
to others' faces and facilitate the detection of
others' expressions (Cordell & McGahan,
2004; Croes et al., 2020; Farroni et al., 2002).
This condition may also favour the occurrence of
yawn contagion between subjects. Indeed, in
species with high exchange of affinitive and
cooperative interactions, contagious yawning
occurs at elevate rates (e.g., chimpanzees,
Campbell & Cox, 2019; Campbell & de
Waal, 2011; bonobos, Palagi et al., 2014; wolves
and do- mestic dogs, Neilands et al., 2020;
Romero et al., 2013; Romero et al., 2014; Silva
et al., 2012; elephant seals,
Wojczulanis-Jakubas et al., 2019; budgerigars,
Gallup et al., 2015). In these species, the
emergence of yawn contagion might be favoured by
natural se- lection in order to promote
synchronization between individuals in spatial
ranging, coordinated foraging, predator
defending and sleep/wake rhythm (Palagi et al.,
2020).
-
- The proximate factors underpinning
contagious yawning are still under debate. For
some researchers, yawn contagion can be the
expression of a motor response whose individual
variation may be related to the different levels
of social attention by the observers
(Attentional Bias Hypothesis, Massen &
Gallup, 2017). In this view, those individuals
that are considered more 'valuable' to the
observer catch his/her attention more than the
less 'valuable' companions do (Massen &
Gallup, 2017; Massen et al., 2012; Yoon &
Tennie, 2010).
-
- On the other hand, the individual
variability in contagious yawning according to
the sex, age and level of familiarity between
sub- jects (see Palagi et al., 2020 for an
extensive review) could be linked to the
individual variability in emotional contagion
(Emotional Bias Hypothesis; Preston & de
Waal, 2002). Following the Perception Action
Model (Preston & de Waal, 2002), emotional
contagion can be considered as a basic form of
empathy defined as '[...] Any process
that emerges from the fact that observers
understand others' states by activating
personal, neural and mental representations of
that state, including the capacity to be
affected by and share the emotional state of
another; assess the reasons for the other's
state; and identify with the other, adopting his
or her perspective' (de Waal & Preston, 2017
p 498). Many neurological studies have
demonstrated the involvement of the mirror
neuron system in the emotional contagion
phenome- non (Decety & Lamm, 2006; Gallese,
2007; Preston & de Waal, 2002; Rizzolatti et
al., 2001; Uddin et al., 2007). The mirror
neuron system is a network of visuomotor neurons
firstly discovered in the area F5 of the macaque
pre-motor cortex (Rizzolatti et al., 1996). In
hu- mans, the mirror neuron system has been
discovered in the premotor, primary
somatosensory and inferior parietal parts of the
cortex (Mukamel et al., 2010; Rizzolatti &
Craighero, 2004). This set of neurons discharges
both when a subject executes a motor action and
when the same subject observes another
individual perform- ing the same motor action
(Ferrari et al., 2003). The firing of mir- ror
neurons causes in the observer a similar
physiological reaction occurring in the
demonstrator thus stimulating a shared process
between subjects. Hence, several studies have
suggested that the mirror neuron system is
involved in emotional sharing and other
empathy-linked phenomena (Decety, 2010; Gazzola
et al., 2006; Hess & Fischer, 2014; Palagi
et al., 2020; Preston & de Waal, 2002;
Prochazkova & Kret, 2017).
-
- In their research, Haker and colleagues
(Haker et al., 2013) employed functional
magnetic resonance imaging to assess human brain
activity in response to others' yawns. When
subjects observed videos of yawning faces as
opposed to faces with a neutral expression,
there was activation in right Brodmann's area 9,
a portion of the right inferior frontal gyrus
which is a region of the mirror neuron sys- tem.
Since Brodmann's area 9 is involved in higher
social cognitive processes (e.g., mentalizing,
Ohnishi et al., 2004), the authors pro- posed
the existence of a linkage between the mirror
neuron system and more complex cognitive
functions such as cognitive empathy. Cognitive
empathy is a top-down process that consciously
evaluates information not directly observable
(e.g., taking another perspective; de Waal &
Preston, 2017). The involvement of higher
cognitive functions, which are not fully
developed at birth, could explain why contagious
yawning occurs later throughout the human
development (Haker et al., 2013). Some
experimental studies on yawn contagion in humans
showed that both infants and preschool children
were not infected by yawns of both familiar and
unfamiliar subjects. Nevertheless, it is worth
noting that children were not exposed to live
stimuli (e.g., colour videotapes of adult
individuals while yawning or smiling; Anderson
& Meno, 2003) and were separated from their
peers during the experiment (e.g., each child
individually tested in a quiet room; Anderson
& Meno, 2003).
-
- Helt and co-workers (Helt et al., 2010), in
order to assess the level of susceptibility to
yawn contagion of both autistic and typically
de- veloping children, employed a different
experimental procedure by exposing subjects to a
live, adult model. Yawn contagion in typically
developing children was almost absent between 1
and 3 years of age and not strongly evident in
children of 4&endash;5 years old (11 out of 40
subjects). In a second set of subjects, the
authors showed that children with autistic
disorders were less susceptible to yawn
contagion compared to typically developing
children.
-
- Hoogenhout and co-authors (Hoogenhout et
al., 2013) investigated whether cuing eye
contact could influence yawn contagion in
children. The authors presented both yawning and
control video clips to the child while an
examiner sat next to the subject by re- minding
him/her to maintain eye contact with the screen.
They re- corded yawning response only in one of
six 3 years old children and seven of 17 older
subjects (4&endash;5 years of age).
- We carried out an ethological study on 129
preschool children aged from 2.5 to 5.5 years
belonging to five different classes of an
Italian public kindergarten. We gathered data on
yawning events by following the children in
their classrooms during their ordinary
activities in order to test some hypotheses on
spontaneous and conta- gious yawning in humans
during the preschool phase.
-
- Hypothesis 1 The effect of age on
spontaneous yawning.
- The frequency of spontaneous yawning during
the 24 h changes throughout human life (Giganti
& Zilli, 2011). For example, in preterm and
near-term infants, the mean rate of yawning over
a 24 h pe- riod is 1.10 yawn/h (Giganti et al.,
2007), whereas in young adults (17&endash;35
years old) this activity is reduced to a mean of
7.1 yawn/day, that is about 0.3 yawn/h
(Baenninger et al., 1996). If, at a finer scale,
the age affects the frequency of spontaneous
yawning also during the preschool phase
(Hypothesis 1a), we predict that spontaneous
yawning is more frequent in younger (2.5 years
of age) than in older children (5.5 years of
age) (Prediction 1a).
- Recently, Gallup and colleagues (Gallup et
al., 2016) demon- strated that both the
frequency and the duration of spontaneous
yawning are variable. The authors showed that,
across mammal spe- cies, the duration of yawning
is strictly correlated with the average brain
weight and cortical neuron number. The
larger-brained mam- mals, such as primates, in
general and humans, in particular, tend to
perform longer yawns than other mammals do.
Furthermore, the duration of spontaneous yawning
seems to be age related, at least in humans,
with adults performing longer yawns than
children (Gallup et al., 2016). During the
preschool years children's brains are growing in
multiple dimensions, including volume, cortical
thick- ness and neural network (i.e., brain
complexity and weight; Brown & Jernigan,
2012; Hagmann et al., 2010; Krogsrud et al.,
2016; Prochazkova & Kret, 2017). If in the
preschool phase the duration of spontaneous
yawning is sensitive to the neural changes
linked to the different ages of children
(Hypothesis 1b), we predict that the duration of
spontaneous yawning increases along with the age
in the preschool period (Prediction 1b).
-
- Hypothesis 2 The effect of age on the
occurrence of yawn contagion.
- Several behavioural studies highlighted the
early develop- ment of emotional contagion in
humans that is largely reflected in emotional
mimicry (Decety, 2010; Leppa_nen & Nelson,
2008; Panksepp & Panksepp, 2013). For
example, newborns and infants become vigorously
distressed by another cry (Dondi et al., 1999;
Trevarthen, 2005) and, from the second half of
the first year of life, children become able to
identify and mimic discrete facial expressions
of emotion such as smiles (Leppa_nen &
Nelson, 2008). The mechanism allowing a child to
reflexively mimic a smile is thought to be the
same allowing the reflexive mimicry of yawning
(Dimberg et al., 2000). Additionally, children
are able to distinguish yawning movements from
other mouth movements from 5 months of age. The
view of yawning motor patterns activates neurons
in the tem- poral areas of 5/8-month-old infants
thus suggesting that the neural mechanism
underpinning yawning perception begins early in
infancy (Tsurumi et al., 2019). If the neural
mechanism allowing children to reflexively mimic
others' yawns has already developed at the
beginning of preschool period (Hypothesis 2a),
we predict that, starting from 3 years of age,
children can not only perceive but also respond
to others' yawns in a congruent manner
(Prediction 2a).
- The ability of children to process others'
facial expressions and, consequently, to
correctly perceive others' emotions seems to
follow a gradual and continuous development
starting from 7 to 8 months of age (Batty &
Taylor, 2006; Grossard et al., 2018; Xie et al.,
2019). Some studies have investigated the length
of the emo- tional processing in human subjects
by recording event-related potentials (Boutet et
al., 2020; Grossard et al., 2018; Kappenman
& Luck, 2012; Xie et al., 2019). Batty and
Taylor (2006) studied the developmental pathway
of facial emotion perception in children
(4&endash;15 years) and found that the latency
in face processing decreased with age. The
authors suggested that, even if the neural
processes involved in the facial expression
recognition and emotional perception are at work
from early childhood, the processing of emotions
develops and matures on a stepwise fashion until
adulthood. If older children (4&endash;5 years
old) have developed more 'neural experience' in
facial expression processing and emotional
perception (Hypothesis 2b), we predict that the
latency in responding to the perceived yawn
decreases along with the increase in age
(Prediction 2b).
-
- Hypothesis 3 The effect of gender on the
distribution of yawn contagion.
- The contagious aspect of yawning shows high
individual variability in humans (Bartholomew
& Cirulli, 2014; Takahiro & Akio, 2018).
Yawn contagion can be affected by different
variables, such as the time of the day (Giganti
& Zilli, 2011), age of the sub- jects
(Bartholomew & Cirulli, 2014) and level of
familiarity between individuals (Norscia &
Palagi, 2011). A 5-year long naturalistic
observation on humans demonstrated that females
were more susceptible to others' yawns than
males (Norscia et al., 2016). The authors
discussed their result in the light of the
empathic nature of yawn contagion and the gender
differences in performing empathy-based
behaviours with females showing higher empathic
abilities. If gen- der affects the sensitivity
to others' yawns in the preschool period
(Hypothesis 3), we predict that in children,
girls show higher levels of contagious yawning
compared to boys (Prediction 3).
-
- Hypothesis 4 The effect of sleep/awake
activity on the fluctuation of spontaneous and
contagious yawning.
-
- The frequency of spontaneous yawning varies
across the day- time with an increase in the
early morning, just after awakening and in the
evening, before sleep (Giganti & Zilli,
2011; Zilli et al., 2008). If also during the
preschool phase the spontaneous yawning is
linked to the sleep/awake cycle (Hypothesis 4a),
we predict that the levels of spontaneous yawns
fluctuate over the 8-h school day by showing a
peak around the sleeping time after lunch
(Prediction 4a). If con- tagious yawning follows
different developmental trajectories com- pared
to spontaneous one (Anderson & Meno, 2003;
Gallup, 2011; Helt et al., 2010; Hoogenhout et
al., 2013; Krestel et al., 2018) (Hypothesis
4b), we predict that the fluctuation of
contagious yawn- ing is not necessarily linked
to the resting/activity phase occurring during
the 8-hr school day (Prediction 4b).
-
- Discussion
- In the current study we employed an
ethological approach for investigating the
dynamics of spontaneous and contagious yawning
in preschool children during their ordinary
activities in their ordinary social context
(i.e., classroom).
-
- As regards spontaneous yawning, our finding
demonstrated that none of the tested variables
affected the duration of the yawning (Prediction
1b not supported) while the variable gender
significantly affected the yawning frequency
distribution with boys showing higher levels of
yawns compared to girls (Prediction 1a not con-
firmed). Several experimental studies
highlighted a strict linkage between sex
hormones and spontaneous yawning frequency. For
example, by treating castrated male rats with
testosterone, the lev- els of their spontaneous
yawning were raised until the normal levels of
intact males (Homgren et al., 1980; Melis et
al., 1994). Moreover, the testosterone provided
to female rats induced an increase also in their
yawning rates (Homgren et al., 1980). In guinea
pigs, daily treatment with testosterone
potentiated the effectiveness of ACTH in
inducing stretch-yawning (Rodriguez-Sierra et
al., 1981). Graves and Wallen (2006)
demonstrated that the treatment with androgen
hormones promoted yawning behaviour in female
rhesus monkeys by increasing their yawning
levels from 0.3 to 4.7 yawn/min. Also, in
Japanese macaques, testosterone induced an
increase in yawning behaviour of males.
Intriguingly, in this study, the increase in
yawning levels positively correlated with the
increase in aggression levels (Bethea et al.,
2013). It has been suggested that in humans, as
in other animals, yawning can be considered as a
sign of increasing arousal or stress in the
subject (Corey et al., 2011; Matikainen &
Elo, 2008; Troisi, 2002; Walusinski, 2006). In a
study carried out by Cordoni et al. (2016) on
the same preschoolers of the current research,
the authors showed that boys of all ages played
in a more competitive manner and engaged in more
aggressive interactions than girls. Another
study on preschool children, by measuring their
salivary testosterone concentration, found a
positive correlation between the levels of the
hormone and serious aggression in boys
(Sa_nchez-Marti_n et al., 2000). Hence, if
spontaneous yawning ex- presses an arousal state
which is linked to testosterone and
aggressiveness, we can speculate that in our
study the higher levels of spontaneous yawning
performed by boys may be due to their higher
levels of arousal. It is worth noting that while
boys showed more spontaneous yawning than girls,
no difference was found in the levels of
contagious yawning according to gender. The same
result was obtained by Campbell and Cox (2019)
for captive chimpanzees. Certainly, further
studies applying both hormonal and behavioural
evaluation are needed for a deeper investigation
of these issues.
-
- Yawning occurs under both spontaneous and
contagious conditions (Provine, 2005). Previous
studies on humans reported that yawn contagion
did not occur below the age of 6 years (Anderson
& Meno, 2003; Helt et al., 2010; Hoogenhout
et al., 2013; Millen & Anderson, 2011). In
the current study, we demonstrated the presence
of yawn contagion in 3-year-old children
(Prediction 2a confirmed).
-
- A yawning event can be a strong releasing
stimulus for a specific behavioural fixed action
pattern that is hard wired and on which is built
the yawn contagion phenomenon (Provine, 1986;
Tinbergen, 1951). In general, by copying
companions' actions children increase the
synchronization of their activities (e.g.,
sleep/awake rhythm) that is a widespread
adaptive phenomenon in human and non-human ani-
mals (Duranton et al., 2017; Duranton &
Gaunet, 2016). Both unconscious and conscious
replication of other's action can be a strategy
to create and strengthen relations with
companions and become part of a social group
(Lakin & Chart rand, 2003; Lakin et al.,
2008). Children synchronize their behaviour to
both identify and affiliate with their group
members (Over & Carpenter, 2012).
-
- Yawn contagion can be also considered an
expression of emo- tional contagion (see Palagi
et al., 2020 for an extensive review). At a
neural level, subcortical brain systems
(including the amygdala) are functional at birth
and have a role in orienting infants' attention
towards others' faces and in enhancing response
activity in specific cortical areas, even though
this function probably does not emerge until the
second half of the first year of life (see
Leppa_nen & Nelson, 2008 for an extensive
review). During early childhood the cortical
connectivity in frontal, parietal and cingulate
areas increases (Long et al., 2017) and shapes
the architecture of the 'future' brain before
full maturation and stabilization (Boutet et
al., 2020). The key components of the
emotion-processing neural network seem to emerge
at this stage, and children develop the capacity
to ex- perience, express and manage emotions
concomitantly with the in- crease in motor
control and cognitive abilities (Decety, 2010;
Tarullo et al., 2009). Taking this evidence into
account, we could argue that, at the beginning
of the preschool phase (3 years of age),
children have already developed the necessary
'neural toolkit' for perceiving others' facial
expressions, copying the motor programme
underpinning those expressions, and therefore
adopting the same emotional state. These phases
of neural maturation are probably at the basis
of the motor replication and subsequent
emotional contagion that allow children to
synchronize their behaviour and develop
affiliation and social bonding with others (Over
& Carpenter, 2012).
-
- The sharing of the natural social setting in
which children ordinarily interact can make
manifest the expression of some phenomena, such
as yawn contagion, thus limiting the inhibition
caused by the experimental apparatus or
unfamiliar setting employed in previous studies
(Anderson & Meno, 2003; Gallup, Church,
Miller, et al., 2016; Helt et al., 2010;
Hoogenhout et al., 2013). Nakahashi and Ohtsuki
(2015) stated that emotional contagion
represents an efficient social learning strategy
when the trigger and the observer share the same
environment or context. In general, individuals
are more prone to automatically replicate the
emotions of in-group than out-group members thus
creating social bonds with companions and,
therefore, improving the probability to become
part of the group (Seyfarth & Cheney, 2013).
Following the 'Like Me' frame- work (Meltzoff,
2007), 'whoever is acting like me, is probably
like me' (Rabinowitch & Knafo-Noam, 2015, p.
8). Children attending kindergarten and sharing
the same environmental and social context can be
affected more by yawns of individuals 'similar
to them', such as classmates, rather than by
yawns of unfamiliar or dissimilar subjects
(e.g., unfamiliar adults; Anderson & Meno,
2003). Those children who developed greater
abilities in identifying and sharing others'
expressions of emotions can be more prosocially
responsive to their peers (Denham et al.,
2003).
- The motor coordination and synchronous
interaction could rep- resent two of the factors
that increase the positive social attitude
between interacting children thus promoting the
development of pro-social behaviours
(Rabinowitch & Knafo-Noam, 2015; Shamay-
Tsoory et al., 2019). A recent study suggested
that motor synchrony, emotional contagion and
conformity (i.e., the alignment with group
actions, thoughts, perception), even though
different phenom- ena, can be intertwined. They
may concur in fostering the social alignment
between group companions, such as classmates
(Social Alignment Model; Shamay-Tsoory et al.,
2019).
-
- Intriguingly, different from mimicry of
other expressions (e.g. play face, Palagi et
al., 2019), yawn contagion usually shows an ex-
tended latency between the emission of the yawn
by the trigger and the motor response by the
observer (chimpanzees, Campbell & Cox, 2019;
humans, Provine, 2005). Outside the primate
order, several studies have shown that yawn
contagion in adults mainly occurs within the
first 90 s after the perception of the stimulus.
In budgerigars (Melopsittacus undulatus), a
social flock-living parrot, individuals show
contagious yawning with a latency of 40 s
(Miller et al., 2012). Yonezawa et al. (2017)
found that sheep yawned within 1 min after the
trigger. Similarly, in canids (i.e., wolves and
dogs) the latency of yawning response was
between 9 and 90 s (Joly- Mascheroni et al.,
2008; Romero et al., 2013). In adult human and
non-human primates, contagious responses peak
within the first minute after the perception of
the stimulus (Norscia & Palagi, 2011; Palagi
et al., 2009, 2014). In the present study,
preschool children, independently from their
age, concentrated the majority of their infected
yawns in the first 2 min after perceiving the
stimulus (Prediction 2b not confirmed). This
finding shows that the latency in the yawning
response is comparable with those recorded for
adult human and non-human primates.
-
- Neither gender nor age influenced the
frequency and the duration of contagious yawns
(Predictions 3 not supported). While spontaneous
yawning can reflect the internal affective state
of the subject (e.g., arousal), the contagious
yawning seems to belong to a communicative
domain. The neural, emotional and behavioural
traits of preschool children are probably not
yet mature to express variability between boys
and girls as well as younger and older children,
although they seem to be already well equipped
with the 'neural toolkit' for ex- pressing yawn
contagion (Decety, 2010; Leppa_nen & Nelson,
2008; Tarullo et al., 2009; Tsurumi et al.,
2019). Probably, the age- and gen- der-related
difference in yawn contagion shown in adults
(Norscia et al., 2016) emerges later in
development of adolescence.
-
- It has been proposed that contagious and
spontaneous yawn- ing can be driven by different
mechanisms (Giganti & Zilli, 2011). In 2011,
Giganti and Zilli demonstrated that in young
people (mean years 22.9 ± 2.7 SD) the
fluctuations of contagious and spontaneous yawns
only partially overlapped, although their
frequencies over the wakefulness period were
both influenced by the hour of the day (i.e.,
early morning and late evening). Our five
kindergarten classes followed the same activity
plan and, thus, the wakefulness period was the
same for all children. According to Giganti and
Zilli (2011), in our study, contagious and
spontaneous yawning followed a partial
overlapped fluctuation (Prediction 4b
supported). Indeed, contagious yawns showed a
clear peak of frequency during the guided
activities (T2), whereas spontaneous yawns
showed a wider peak of frequency from T2 to T4
(Prediction 4a not supported). However, we have
to un- derline that our analysis was limited to
the 8-hr school day. Further studies are needed
to obtain more complete data on the frequency of
both types of yawn during the day time.
-
- In conclusion, physiological, neural and
behavioural approaches are needed to draw the
possible ontogenetic trajectories and modulation
of yawn contagion in humans. Yet, we encourage
observations carried out under naturalistic
conditions that could complement the more
controlled approaches carried out under
laboratory conditions. Observations in the real
world may reveal patterns not found in
inherently artificial experimental settings.
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