Why Yawning is Contagious
Contagious yawning occurs because observing someone yawn triggers involuntary activation of the mirror neuron system in the brain, particularly in regions involved in motor imitation and empathy, with individual susceptibility determined by cortical excitability and physiological inhibition in the primary motor cortex. 1
Neural Mechanisms
Mirror Neuron System Activation
- Viewing someone yawn activates the mirror neuron system, specifically the right inferior frontal gyrus (Brodmann's area 9), which allows two individuals to share physiological and emotional states based on perceived motor patterns. 2
- The posterior cingulate and precuneus—brain regions involved in self-referential processing, theory of mind, and autobiographical memory—show unique neural activity when viewing someone yawn. 3
- This neural substrate represents a component of motor empathy that underlies cognitive empathic functions. 2
Cortical Excitability and Individual Variability
- Individual propensity for contagious yawning is determined by motor cortical excitability and physiological inhibition in the primary motor cortex, which accounts for approximately 50% of the variability in contagious yawning susceptibility. 1
- Transcranial magnetic stimulation studies demonstrate that measures of cortical excitability and physiological inhibition are significant predictors of how susceptible someone is to contagious yawning. 1
- Instructions to resist yawning increase the urge to yawn and alter yawn expression (full versus stifled yawns) but do not change the underlying individual propensity for contagious yawning. 1
Connection to Empathy
Evidence Supporting the Link
- Subjects who yawn in response to observing others yawn exhibit higher empathy values by half a standard deviation compared to those who do not yawn contagiously. 4
- Among various facial expressions (yawning, scratching, laughing), only contagious yawning shows a relationship to empathy as measured by the Interpersonal Reactivity Index. 4
- The activation of BA 9 during contagious yawning emphasizes the connection between the mirror neuron system and higher cognitive empathic functions, including mentalizing abilities. 2
Important Caveats
- The overall evidence linking contagious yawning to empathy remains inconsistent and inconclusive, with confounding variables such as visual attention and social inhibition affecting study results. 5
- While contagious yawning relates to empathy, there is no evidence that susceptibility to contagious yawning directly relates to prosocial behavior. 4
- The conceptual basis for the proposed connection between contagious yawning and empathy requires more rigorous investigation with objective measurements. 5
Clinical Relevance
- Contagious yawning represents a form of echophenomena—the automatic imitation of another's actions (echopraxia)—which has been proposed to link to disinhibition of the human mirror neuron system and hyper-excitability of cortical motor areas. 1
- Understanding the neural basis of contagious yawning provides insight into broader mechanisms of social cognition, motor imitation, and empathic processing in the human brain. 3, 2