Why is yawning contagious?

One person opens their mouth, takes a long breath, and yawns. A few seconds later, someone else in the room does the same. Sometimes you do not even need to see the yawn. Hearing it, reading about it, or simply thinking about yawning can be enough to trigger the urge.

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Contagious yawning appears to occur because the brain recognises another person’s yawn and activates networks involved in attention, action preparation, and social processing. The response is not deliberate, and it is not caused by a sudden lack of oxygen. Some people are highly susceptible, while others rarely yawn in response. Social closeness, attention, age, and individual nervous-system differences may influence the reaction, but contagious yawning is not a reliable test of empathy.

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A yawn is a coordinated motor pattern

Yawning is more than opening the mouth and taking a deep breath.

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A typical yawn may involve:

• Slow, deep inhalation

• Wide opening of the mouth

• Expansion of the throat

• Movement of the jaw

• Contraction of facial muscles

• Partial closing of the eyes

• Stretching of the neck or upper body

• A slower exhalation

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Some people also stretch their arms, back, or legs at the same time. The combination of yawning and stretching is sometimes called pandiculation.

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Once a yawn has started, it can be difficult to stop halfway through.

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This suggests that yawning is organised as a coordinated motor programme within the nervous system rather than as a series of separate voluntary movements.

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Yawning occurs in humans and many other vertebrates. It can arise spontaneously, but in some social species it may also be triggered by observing another individual.

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Spontaneous and contagious yawning are different

Spontaneous yawning occurs without first observing someone else.

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It commonly appears during transitions in alertness, such as:

• Before sleep

• After waking

• During boredom

• During monotonous activity

• When attention levels change

• Before stressful or demanding events

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Contagious yawning occurs after seeing, hearing, reading about, or imagining a yawn.

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Both forms probably use overlapping motor pathways once the yawn itself begins, but the trigger is different.

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Spontaneous yawning is mainly linked to the person’s own physiological state. Contagious yawning begins with an external or imagined signal.

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A person may yawn frequently when tired but rarely respond to someone else’s yawn. Another may be strongly affected by social yawning even when not particularly sleepy.

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Yawning is not caused by low oxygen

A common explanation is that yawning occurs because the body needs more oxygen or must remove excess carbon dioxide.

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The idea seems plausible because a yawn includes a deep inhalation.

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Controlled studies have not supported a simple oxygen-deficiency explanation.

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If yawning primarily corrected blood-gas levels, changing oxygen and carbon dioxide concentrations should reliably alter yawning frequency. This has not been demonstrated consistently.

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The breath taken during a yawn does change ventilation briefly, but that does not mean low oxygen caused the response.

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A poorly ventilated, warm, or monotonous room may still make people more tired and therefore more likely to yawn. The mechanism is more likely related to alertness, temperature, and attention than to acute oxygen deprivation.

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Real breathing difficulty, blue lips, chest pain, or reduced consciousness should never be dismissed as ordinary yawning.

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Seeing a yawn can create an automatic urge

When you see another person yawn, the brain automatically analyses the facial movement.

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Systems involved in face perception, biological movement, and action recognition identify the characteristic opening of the mouth and changes around the eyes.

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In susceptible individuals, this can trigger a gradually increasing urge to yawn.

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The urge may be experienced as:

• Tension in the jaw

• A need to open the mouth

• A deeper inhalation

• Stretching in the throat

• A feeling that the yawn must be completed

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Trying to suppress it can sometimes make the urge feel stronger.

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The person directs more attention towards the early bodily sensations and becomes more aware of them.

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This resembles other urges that become harder to ignore once attention is focused on them, such as itching, blinking, or throat clearing.

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Sound can also trigger the response

Contagious yawning is not dependent on vision.

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Research has shown that hearing another person yawn can increase both the urge to yawn and the number of actual yawns.

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A yawn produces a recognisable breathing pattern and characteristic sound from the mouth and throat. The brain can identify this signal without seeing the person.

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Possible triggers therefore include:

• A visible yawn

• The sound of a yawn

• A photograph

• A video

• Written descriptions

• Imagining someone yawning

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This shows that the response is not simply a mechanical copying of a visible facial expression.

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Several sensory and cognitive pathways can activate the representation of yawning.

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Reading a detailed article about yawning may therefore increase the likelihood that the reader yawns before reaching the end.

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Attention is necessary

People do not respond to every yawn that occurs around them.

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If attention is focused on a demanding task, a yawn in the background may not be processed strongly enough to trigger a response.

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For contagious yawning to occur, the brain usually needs to register the signal clearly enough to identify it.

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Susceptibility may therefore depend on:

• Whether the face is clearly visible

• How long the yawn is observed

• Whether the person is distracted

• Existing tiredness

• Expectations

• Attempts to suppress the response

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This makes research difficult.

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A participant who does not yawn during an experiment may have low biological susceptibility, but they may also have been distracted, socially inhibited, or unwilling to yawn in front of others.

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Absence of a visible yawn cannot therefore be interpreted as a direct measure of one psychological trait.

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Action-observation systems may contribute

When people observe an action, some brain regions involved in planning or performing similar movements may also become active.

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These processes are often discussed in relation to mirror-neuron systems or action-observation networks.

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One hypothesis is that seeing a yawn activates a motor representation of the same action. If the activation becomes strong enough, the person may perform a yawn.

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Brain-imaging studies suggest that contagious yawning involves regions linked to:

• Action preparation

• Social perception

• Self-related processing

• Attention

• Emotional significance

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It would still be too simple to say that mirror neurons fully explain contagious yawning.

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The involved brain regions perform many functions, and brain-imaging activity alone cannot prove the exact mechanism.

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Action mirroring is therefore one possible component rather than a complete explanation.

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The response may help synchronise a group

One evolutionary hypothesis is that contagious yawning helps coordinate alertness and behaviour within a social group.

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If one individual becomes tired or changes state, the yawn may act as a signal to others.

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A spreading response could potentially help synchronise:

• Rest periods

• Waking periods

• Group movement

• Attention

• Changes in activity

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This hypothesis is difficult to test directly in humans.

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A behaviour may also have more than one function, and its present-day effect does not necessarily reveal why it originally evolved.

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Contagious yawning may result from several overlapping mechanisms rather than one specific adaptation.

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Social closeness may influence contagious yawning

Several observational studies have examined whether yawning spreads more easily between people who know each other well.

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Some have reported stronger contagion between:

• Family members

• Close friends

• Partners

• Familiar individuals

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One explanation is that people pay more attention to individuals who are socially important to them.

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The movements and expressions of close others may also be processed as more relevant.

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Social closeness is difficult to separate from other factors, including:

• Eye contact

• Time spent together

• Familiarity with the person’s behaviour

• Comfort with yawning openly

• Shared environment

• Age

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A higher response between friends does not necessarily mean that empathy alone caused the difference.

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Attention, familiarity, and social safety may be equally important.

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Contagious yawning is not a simple empathy test

Contagious yawning is often presented as a biological measure of empathy.

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The idea is based on findings that yawning can spread socially, may be stronger between close individuals, and occurs in some highly social animal species.

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Some studies have found associations between yawning susceptibility and measures of social cognition.

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Other studies have failed to reproduce those results.

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Important methodological limitations include:

• Small sample sizes

• Different definitions of empathy

• Different ways of presenting yawns

• Limited control of attention

• Social suppression of yawning

• Large individual variability

• Publication bias

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The most accurate conclusion is that contagious yawning may involve social information processing, but it is not a reliable measure of how empathic a person is.

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Someone who does not yawn in response is not necessarily less caring, less emotionally responsive, or less socially aware.

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Children develop the response gradually

Babies and young children yawn spontaneously.

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Contagious yawning appears to develop later.

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Younger children often respond less consistently to other people’s yawns than older children and adults.

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The response may become more evident as several abilities develop:

• Attention to faces

• Recognition of biological movement

• Social understanding

• Action imitation

• Interpretation of other people’s behaviour

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Studies differ in the age at which contagious yawning becomes clearly measurable.

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The variation may reflect different methods, observation periods, and developmental differences between children.

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Failure to yawn contagiously in a young child is not by itself evidence of a developmental disorder.

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The response should never be used alone to assess empathy, social ability, or neurological development.

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Autism research has often been oversimplified

Some early studies reported lower contagious-yawning rates in autistic participants.

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These findings were sometimes interpreted as evidence of reduced empathy.

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Later research showed that attention to the face, and particularly the eye region, may strongly influence whether the yawn is registered.

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When attention is directed towards the relevant signal, differences may become smaller or disappear in some studies.

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Autism also includes wide variation in sensory processing, attention, communication, and social behaviour.

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Empathy itself contains several components, including:

• Emotional response

• Perspective-taking

• Concern for others

• Recognition of distress

• Supportive behaviour

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A single yawn cannot measure this complexity.

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It is therefore inaccurate and potentially harmful to interpret lower contagious yawning as evidence that autistic people lack empathy.

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Some people are more susceptible than others

Individual differences in contagious yawning are substantial.

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Some people yawn almost immediately after seeing another person do it. Others rarely respond.

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Possible influences include:

• Age

• Sleepiness

• Attention

• Social context

• Individual nervous-system activity

• Expectations

• Ability to suppress the response

• Strength of the stimulus

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Some studies suggest that susceptibility decreases somewhat with age.

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Age explains only a small proportion of the total variation.

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The same person may also respond during one experiment and not another.

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Contagious yawning should therefore be understood as a probability-based response, not as a reflex that is triggered every time.

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Can the yawn be suppressed?

A person can sometimes suppress or reduce a yawn.

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They may try to:

• Keep the mouth closed

• Tighten the jaw

• Breathe through the nose

• Look away

• Redirect attention

• Cover the mouth

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Suppressing the movement does not always remove the urge.

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The yawn may return shortly afterwards or appear as a smaller, incomplete movement.

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Social rules strongly influence whether the response becomes visible.

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During a meeting, lesson, or conversation, someone may hide the yawn because it could be interpreted as boredom or disrespect.

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Observed yawns therefore do not perfectly represent the underlying biological urge.

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Two people may experience equally strong contagious yawning while displaying it very differently.

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Yawning does not always mean boredom

Yawning is strongly associated with boredom, but the relationship is not direct.

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Monotonous activity can reduce alertness and make yawning more likely.

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Yawning can also occur when someone is:

• Nervous

• Preparing for competition

• Mentally overloaded

• Trying to remain awake

• Transitioning between activities

• Responding to another person’s yawn

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An athlete may yawn before an important event without being relaxed or uninterested.

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A student may yawn during an engaging lecture because of sleep deprivation.

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The yawn reflects a change in physiological or attentional state more reliably than it communicates boredom.

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Interpreting another person’s motivation from one yawn is therefore unreliable.

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Brain-temperature regulation is another hypothesis

Another theory proposes that yawning contributes to temperature regulation in and around the brain.

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The movement may influence:

• Facial blood flow

• Jaw movement

• Air intake

• Heat exchange

• Circulation around the head

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Some studies have found that yawning frequency changes with environmental temperature.

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The theory proposes that yawning may be most useful within a particular temperature range, when incoming air and changes in blood flow can support cooling.

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The hypothesis is interesting but not established as the sole explanation for human yawning.

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Even if spontaneous yawning contributes to thermoregulation, this does not fully explain why seeing or hearing another yawn triggers the same response.

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A separate social or perceptual mechanism is still required.

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Yawning can occur before demanding events

Yawning sometimes appears before situations that require attention, effort, or stress regulation.

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Examples include:

• Athletic competition

• Public speaking

• Medical procedures

• Parachute jumps

• Examinations

• High-pressure performances

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This seems inconsistent with the idea that yawning always reflects low arousal.

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The body may be transitioning between states of activation, and yawning may form part of that adjustment.

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It may also result from waiting, anticipatory stress, altered breathing, or changes in attention.

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A yawn before an important event does not necessarily indicate tiredness or lack of motivation.

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Other species also show contagious yawning

Contagious yawning has been reported in several social species.

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Examples include:

• Chimpanzees

• Bonobos

• Dogs

• Some other primates

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Researchers have examined whether the response is influenced by familiarity, group membership, age, attention, and stress.

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Results vary between species and studies.

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It is difficult to determine whether an animal yawns because of social contagion, general arousal, stress, or chance.

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The findings still suggest that contagious yawning is not unique to humans.

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An animal yawning after a human does not automatically prove human-like empathy. Several competing explanations remain possible.

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Contagious laughter and yawning are not identical

Both laughter and yawning can spread through a group, but the behaviours differ.

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Laughter is strongly linked to social communication, humour, play, and emotional interaction.

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Yawning is more stereotyped and may occur without a clear communicative intention.

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Contagious laughter	Contagious yawning
Strongly shaped by humour and mood	Can be triggered by sight, sound, or thought
Highly communicative	May occur without deliberate communication
Expression varies considerably	Motor pattern is relatively stereotyped
Usually linked to emotional context	Does not require a specific emotion

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Both show that nervous systems respond to other people’s behaviour.

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The underlying mechanisms are not necessarily the same.

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Frequent yawning may have other causes

Contagious yawning is normal.

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Very frequent yawning without an obvious social trigger may be associated with:

• Sleep deprivation

• Sleep apnoea

• Shift work

• Sedating medication

• Some antidepressants

• Migraine

• Stress

• Reduced alertness

• Rare neurological or cardiovascular conditions

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Frequent yawning alone is usually not evidence of serious illness.

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The context, timing, and accompanying symptoms matter.

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If poor sleep is the main cause, treating the sleep problem is more relevant than trying to suppress the yawning itself.

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Medication should not be stopped without professional guidance, even if yawning began after treatment was started.

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When frequent yawning should be assessed

Medical assessment may be appropriate when yawning is new, extreme, persistent, or accompanied by other symptoms.

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Relevant symptoms include:

• Severe daytime sleepiness

• Uncontrolled episodes of falling asleep

• Loud snoring and breathing pauses

• Dizziness or fainting

• Chest pain

• Palpitations

• New neurological symptoms

• Severe or unusual headache

• Symptoms beginning after a medication change

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Sudden yawning accompanied by facial weakness, speech difficulty, limb weakness, severe dizziness, or reduced consciousness should not be explained as ordinary contagious yawning and requires urgent assessment.

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For most people, however, yawning in response to another person is simply a normal variation in social and sensory processing.

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Summary

Yawning is contagious because seeing, hearing, reading about, or imagining a yawn can activate brain systems involved in attention, action preparation, and social processing. The response is not caused by low oxygen and is not a deliberate imitation. Social closeness, familiarity, attention, age, and individual nervous-system differences may influence how easily a person responds. Although contagious yawning may involve social information processing, it is not a reliable test of empathy. Some people are highly susceptible, while others rarely respond, and both patterns are normal.

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Sources

• Massen JJM, Gallup AC. Why contagious yawning does not (yet) equate to empathy. Neuroscience & Biobehavioral Reviews. 2017;80:573–585.

• Arnott SR, Singhal A, Goodale MA. An investigation of auditory contagious yawning. Cognitive, Affective, & Behavioral Neuroscience. 2009;9(3):335–342.

• Haker H, Kawohl W, Herwig U, Rössler W. Mirror neuron activity during contagious yawning: An fMRI study. Brain Imaging and Behavior. 2013;7(1):28–34.