Everybody yawns. Even our pets. Scientists have proposed several reasons for the phenomenon.Everybody yawns. .In humans, yawning appears to be caused by physiological and psychological factors.
Physically, yawning involves opening the mouth, inhaling air, opening the jaw, stretching the eardrums, and exhaling. It can be triggered by fatigue, boredom, stress or seeing someone yawning.As a reflex, yawning involves an interaction of neurotransmitters associated with tiredness, appetite, tension and emotions. These chemicals include nitric oxide, serotonin, dopamine and glutamic acid.
Scientists know that certain medical conditions (eg, multiple sclerosis, stroke, and diabetes) alter the frequency of yawning and cortisol levels in saliva following a yawn.Because yawning is a matter of neurochemistry, there are several possible reasons that can happen. In animals, some of these reasons are easily understood. For example, snakes yawn to realign their jaws after eating and to help with breathing.
Fish yawn when their water does not have enough oxygen. Determining why humans yawn is harder to identify. As cortisol levels increase after yawning, this may increase alertness and indicate the need for action.
Psychologists Andrew Gallup and Gordon Gallup believe that yawning helps improve blood flow to the brain. The premise is that jaw lengthening increases blood flow to the face, head, and neck, while deep yawning breathing forces blood and spinal fluid to flow downward. This physical basis for yawning may explain why people yawn when they are anxious or stressed. Parachutists yawn before leaving the aircraft.
Gallup research also indicated that yawning helps cool the brain, while cooler, inhaled air cools the blood forced to flow during yawning. Gallup’s studies included experiments on parakeets, rats, and humans.The team found that people yawn more when the temperature is lower. Rat brains cooled slightly when the animals yawned.
To date, more than 20 psychological reasons for yawning have been proposed. However, there is little agreement in the scientific community about which hypotheses are correct.
Yawning can serve a social function, particularly as a herd instinct. In humans and other vertebrates, yawning is contagious. Captive yawning can communicate fatigue to members of a group, helping people and other animals synchronize wakefulness and sleep patterns.
Alternatively, it may be a survival instinct. The theory, according to Gordon Gallup, is that contagious yawning can help members of a group become more alert so they can detect and defend against attackers or predators.
In his book The Expression of Emotions in Man and Animals, Charles Darwin observed baboons yawning to threaten enemies. Similar behavior has been reported in fish and guinea pigs. At the other end of the spectrum, Adelie penguins yawn as part of their dating ritual.
A study by Alessia Leone and her team suggests that there are different types of yawning to convey different information (eg empathy or anxiety) in a social context. Leone’s research involved a type of monkey called cold, but it is possible that human yawns also vary according to their function.
Which theories are correct?
It is clear that yawning is caused by physiological factors. Fluctuations in neurotransmitter levels cause yawning. The biological benefits of yawning are clear in some other species, but not so obvious in humans.
At the very least, yawning quickly increases alertness. In animals, the social aspect of yawning is well documented. While yawning is contagious in humans, researchers still need to determine whether yawning psychology is a remnant of human evolution or whether it still serves a psychological function today