In the BBC reality show The Celebrity Traitors, the Traitors – James Acaster, Maya Jama and King Kenny – were set an unusual challenge: murder a Faithful by making them yawn. Their plan was to bore their target into yawning, then deliver the line “Am I boring you?” to seal the murder.
The task plays on one of yawning’s strangest features: its ability to spread from one person to another. Seeing someone yawn can be enough to trigger a yawn of your own, sometimes even when you are not tired. But would the same trick work if the yawn were deliberately faked?
Yawning is found across the animal kingdom and scientists believe that the behaviour dates back hundreds of millions of years. Humans yawn, but so do apes, dogs, horses, reptiles, birds and even fish, although contagious yawning – catching a yawn from another individual – is found in far fewer species.
Why do yawns spread, and what does this tell us about how we respond to other people? Researchers have several theories, from social bonding to the brain mechanisms involved in recognising and copying others’ actions. These may help explain whether a convincing fake yawn can fool us – and whether the Traitors’ task was as easy as it sounds.
One idea is known as the social bonding hypothesis. Humans and many social animals often copy each other’s behaviour without realising it. We mimic facial expressions, gestures, postures and even accents. This unconscious imitation can help strengthen social connections and create a sense of belonging.
Contagious yawning may be another example of this social mimicry. Studies have found that people are more likely to catch yawns from family members, friends and people they know well than from strangers. Similar patterns have been noted in other social animals. Wolves, for example, are more likely to respond to yawns from individuals with whom they have stronger social bonds.
Researchers have also reported that social status can influence contagious yawning. Individuals may be more responsive to members of their own group or to higher status group members, but responses are often weaker towards unfamiliar outsiders. This suggests that contagious yawning may reflect underlying social relationships.
Mirror neurons and mental simulation
A second theory focuses on the brain mechanisms that help us understand the behaviour of others. Some researchers have linked contagious yawning to the activity of so-called mirror neurons. These become active both when we perform an action and when we observe someone else performing the same action, and may help us understand the actions, intentions and feelings of other people.
According to this view, seeing somebody yawn effectively primes our own yawning system, making us more likely to yawn in response. A related idea is that contagious yawning may be linked to emotional contagion, the tendency to share the feelings and states of others. In this account, contagious yawning is related to empathy: our ability to understand and respond to another person’s experiences.
Several findings support this possibility. Contagious yawning typically emerges around the age of four or five years, roughly the same period when children develop more advanced abilities to understand what other people are thinking and feeling – often termed “mentalising”.
Reduced contagious yawning has been reported in people with autism and in those with psychopathic traits. However, while this finding fits the popular narrative for these conditions, the picture is not straightforward.
In autism, reduced contagious yawning may not necessarily reflect reduced empathy. Some studies suggest that differences in attention, particularly spending less time looking directly at faces and eyes, may account for much of the effect. In other words, if someone is not closely watching the yawner’s face, they may simply be less likely to detect the trigger for contagious yawning.
So, are fake yawns contagious?
The answer is “sometimes”, but less effectively than is the case for genuine yawns.
If contagious yawning depends partly on automatic social and emotional responses, then a convincing fake yawn may still trigger the same brain mechanisms as a real one. After all, the observer often responds to the appearance of a yawn rather than knowing whether it is genuine.
However, if the yawn looks obviously artificial or exaggerated, key social signals may be missing. The observer may not unconsciously simulate the action or interpret it as a genuine expression of another person’s state. As a result, the contagious effect may be weaker or absent.
In short, contagious yawning appears to be about more than simply seeing an open mouth. It may reflect social connection, shared attention and subtle emotional communication. For that reason, a fake yawn may be contagious when it looks authentic, but an obviously fake yawn is less likely to trigger the social mechanisms that make real yawns spread from person to person.
For the Traitors, that leaves a tricky question: could they make their target yawn without making it obvious that they were trying to do so? Their success depended on exploiting a behaviour that is partly automatic – but not entirely predictable.
Stephen Jackson receives funding from the Medical Research Council, Parkinson’s UK, Action Medical Research, and Neurotrherapeutics Ltd.