Why do we yawn? Why is yawning contagious?

Recent research has shown that yawning has a temperature-regulating effect on the brain. According to this view, the deep breath taken by yawning-like a radiator in a car - keeps the brain cool. When brain temperature increases, blood flow in the nasal mucosa accelerates. The air taken by yawning changes the temperature of the blood in the veins as it passes through the nasal and oral cavity-the walls of which are covered by blood vessel networks directly connected to the forebrain. So it helps the brain cool down. Research on mice showed that the brain temperature increased before yawning, and then the temperature dropped. However, the temperature stabilizing effect of yawning was more pronounced at average temperatures (about 20°C) where the ambient temperature was not extremely hot or extremely cold.

So why do we usually yawn before we go to sleep, after we wake up, or when we're bored? The brain is responsible for 2% of body weight and 20% of total energy consumption. Sleep and stress are thought to cause changes in brain temperature. Insomnia, for example, is known to increase brain temperature. The reason yawning is associated with sleep and fatigue may be its effects on brain temperature.

Yawning is also contagious. Witnessing someone else yawning or reading about yawning can trigger yawning. The fact that yawning is contagious is thought to be associated with a sense of empathy. Studies using brain imaging methods showed that during infectious yawning, the area in the brain where people's own emotions and other people's emotions are evaluated is active. There are also studies that yawning is contagious and has no apparent connection to empathy. However, fewer sightings of infectious yawning in individuals with autism and schizophrenia patients with impaired social communication skills support the view that yawning is contagious and is associated with a sense of empathy.