A yawn involves a deep inhalation accompanied by a gaping mouth, squinted eyes and sometimes stretching. The average yawn lasts six seconds and is commonly related to situations of boredom or tiredness. However, it also occurs upon waking up, and athletes and musicians have been observed yawning before performing.
Yawning is associated with tiredness, stress, overwork, lack of stimulation, or boredom. Yawning can also be a powerful non verbal message with several possible meanings, depending on the circumstances. In humans, yawning has an infectious quality. Seeing a person yawning, or just thinking of yawning, can trigger yawning which is a typical example of positive feedback. The exact causes of yawning are still undetermined. The claim that yawning is caused by lack of oxygen has not been substantiated scientifically. Another speculated reason for yawning is nervousness and is also claimed to help increase the state of alertness of a person. Paratroopers have been noted to yawn in the moments before they exit an aircraft.
The yawn reflex is often described as contagious. If one person yawns, this may cause another person to sympathetically yawn. Observing another person’s yawning face, thinking about yawning, or even reading this blog entry, can cause you or another person to yawn. The cause for contagious yawning may lie with mirror neurons in the frontal cortex, which upon being exposed to a stimulus from the same species can activate similar regions in the brain.
Mirror neurons have been proposed as a driving force for imitation which lies at the root of much human learning such as language. Yawning may be an offshoot of the same imitative impulse. A 2007 study found that children with autism do not increase their yawning frequency after seeing videos of other people yawning. This supports the claim that contagious yawning is based on the capacity for empathy.
Recently, researchers from the University of Albany proposed that yawning may be a means to keep the brain cool. Mammalian brains operate best within a narrow temperature range. In two experiments, they demonstrated that subjects with cold packs attached to their foreheads and when asked to breathe nasally exhibited reduced contagious yawning when watching videos of people yawning. A similar recent hypothesis is that yawning is used for regulation of body temperature.
Another hypothesis is that yawns are caused by the same neurotransmitters in the brain that affect emotions, mood, appetite, and other phenomena. These chemicals include serotonin, dopamine, glutamic acid, and nitric oxide. As more or less of these compounds are activated in the brain, the frequency of yawning increases. Conversely, a greater presence in the brain of opiate neurotransmitters such as endorphins reduces the frequency of yawning.
Anecdotal reports by users of psilocybin mushrooms often describe a marked stimulation of yawning while intoxicated, especially while undergoing the most intense portion of the psilocybin experience. While opioids have been demonstrated to reduce this yawning provoked by psilocybin, it is not clear that the same pathways that induce yawning as a symptom of opioid abstinence in habituated users are the mode of action in yawning in mushroom users.
Recent research carried out by Catriona Morrison, a lecturer in psychology at the University of Leeds, involving monitoring the behavior of students kept waiting in a reception area, indicates a connection between empathic ability and yawning. She found that contagious yawning indicates empathy and an appreciation of other people’s behavioral and physiological state.
Yet another theory is that yawning occurs to stabilize pressure on either side of the ear drum. The deep intake of air can sometimes cause a popping sound that only the yawner can hear. This is the pressure on the middle ear such as inside an airplane and when travelling up and down hills, which cause the eardrums to be bent instead of flat. Some people yawn when storms approach, which is a sure sign that changes in pressure affect them.
Some movements in psychotherapy believe that yawning, along with laughter and crying, are means of discharging painful emotion, and therefore can be encouraged in order to promote physical and emotional changes.
Certain superstitions surround the act of yawning. The most common of these is the belief that it is necessary to cover one’s mouth when one is yawning in order to prevent one’s soul from escaping the body. The Ancient Greeks believed that yawning was not a sign of boredom, but that a person’s soul was trying to escape from its body, so that it may rest with the gods in the skies. This belief was also shared by the Maya.