A portion of the brain that plays an important role in triggering the yawn is the hypothalamus (where are also guarded the centers that synchronize sleep and wakefulness, hunger and thirst, body temperature). In particular, some neurotransmitters (including dopamine) and neuropeptide have an important role in stimulating this behavior. Yawn is a stereotyped behaviour and there are not differences of sex, race, age in the way you yawn: there is a long inhalation followed by a brief exhalation during which it is very difficult, almost impossible, to avoid opening your mouth and get some ‘air. Throughout the average yawn lasts six seconds. It is the empathy that makes us not resist a yawn when we see someone do it in front of us and the phenomenon affects up to 60% of people. The psychologist Steven Platek of Drexel University in Philadelphia in Pennsylvania said that it is a behaviour done in unconscious way, and imitating them is the result of the ability to identify in the mental state of another person. Platek investigated the phenomenon yawn recruiting a group of people and making them look a series of videos that people sent in the yawn or simply during conversations on the subject yawn. Within a short time from 40 to 60% of viewers do not stand up and begin to yawn themselves. According to the researchers who are immune to infection and not yawning as the others are just individuals with little ability to get in the shoes of others, individuals who lack the human characteristic of showing empathy for others. Ronald Baenninger, expert and author of research on yawning at Temple University in Philadelphia, commenting on the news, claims that the results are explained by evolutionary point of view. In fact, he says, the contagious yawning may have helped our ancestors to coordinate the periods of activity and rest. “It is important that all members of a group – says Baenninger-are ready to do the same thing contemporaneously.” Even with this research, however, emphasize the two experts, the causes of the phenomenon yawn are not yet fully clarified. For those who consider the yawn is the effect of lack of oxygen and, therefore, need to inhale more deeply, the denial came from studies that showed no significant difference between the frequency of yawning rooms in poor or rich in oxygen. Baenninger concludes that it is more likely to think yawn as a measure to face involuntary keep awake to the brain, not by chance yawn when fighting sleep at night when we must continue to engage, or in the morning when we win sleep and take action.