Humour 2

Laughter is a typically pleasant physical reaction and emotion consisting usually of rhythmical, usually audible contractions of the diaphragm and other parts of the respiratory system. It is a response to certain external or internal stimuli. Laughter can rise from such activities as being tickled, or from humorous stories, imagery, videos or thoughts.Most commonly, it is considered an auditory expression of a number of positive emotional states, such as joy, mirth, happiness or relief. On some occasions, however, it may be caused by contrary emotional states such as embarrassment, surprise, or confusion such as nervous laughter or courtesy laugh. Age, gender, education, language and culture are all indicators as to whether a person will experience laughter in a given situation. Other than humans, some other species of primate (chimpanzees, gorillas and orangutans) show laughter-like vocalizations in response to physical contact such as wrestling, play chasing or tickling.

Laughter is a part of human behaviour regulated by the brain, helping humans clarify their intentions in social interaction and providing an emotional context to conversations. Laughter is used as a signal for being part of a group - it signals acceptance and positive interactions with others. Laughter is sometimes seen as contagious and the laughter of one person can itself provoke laughter from others as a positive feedback. 

The study of humour and laughter, and its psychological and physiological effects on the human body, is called gelotology.

Laughter might be thought of as an audible expression or appearance of excitement, an inward feeling of joy and happiness. It may ensue from jokes, tickling, and other stimuli completely unrelated to psychological state, such as nitrous oxide. One group of researchers speculated that noises from infants as early as 16 days old may be vocal laughing sounds or laughter.However, the weight of the evidence supports the appearance of such sounds at 15 weeks to four months of age.

Laughter researcherRobert Provin esaid: "Laughter is a mechanism everyone has; laughter is part of universal human vocabulary. There are thousands of languages, hundreds of thousands of dialects, but everyone speaks laughter in pretty much the same way." Babies have the ability to laugh before they ever speak. Children who are born blind and deaf still retain the ability to laugh. 

Provine argues that "Laughter is primitive, an unconscious vocalization." Provine argues that it probably is genetic. In a study of the "Giggle Twins", two happy twins who were separated at birth and only reunited 43 years later, Provine reports that "until they met each other, neither of these exceptionally happy ladies had known anyone who laughed as much as they did." They reported this even though they had been brought together by their adoptive parents, who they indicated were "undemonstrative and dour". He indicates that the twins "inherited some aspects of their laugh sound and pattern, readiness to laugh, and maybe even taste in humour".

Scientists have noted the similarity in forms of laughter induced by tickling among various primates, which suggests that laughter derives from a common origin among primate species. 

The spotted hyena, another species of animal, was also known as the laughing hyena because of the way it sounds when it communicates.

A very rare neurological condition has been observed whereby the sufferer is unable to laugh out loud, a condition known as aphonogelia. 

Neurophysiology indicates that laughter is linked with the activation of the ventromedial prefrontal cortex, that produces endorphins. Scientists have shown that parts of the limbic system are involved in laughter. This system is involved in emotions and helps us with functions necessary for humans' survival. The structures in the limbic system that are involved in laughter are the hippocampu sand the amygdala. 

The December 7, 1984,Journal of the American Medical Association describes the neurological causes of laughter as follows:

"Although there is no known 'laugh centre' in the brain, its neural mechanism has been the subject of much, albeit inconclusive, speculation. It is evident that its expression depends on neural paths arising in close association with the telencephalic and diencephalic centres concerned with respiration. Wilson considered the mechanism to be in the region of the mesial thalamus, hypothalamus, and sub thalamus. Kelly and co-workers, in turn, postulated that the tegmentum near the periaqueductal grey contains the integrating mechanism for emotional expression. Thus, supranuclear pathways, including those from the limbic system that Papez hypothesised to mediate emotional expressions such as laughter, probably come into synapticrelation in the reticular core of the brain stem. So while purely emotional responses such as laughter are mediated by subcortical structures, especially the hypothalamus, and are stereotyped, the cerebral cortex can modulate or suppress them."

Some drugs are well known for their laughter-facilitating properties (e. g. ethanol and cannabis), while the others, likes alvinorin A(the active ingredient ofSalvia divinorum), can even induce bursts of uncontrollable laughter.[16]

A research article was published December 1, 2000, on the psycho-evolution of laughter (Panksepp 2000). 

A link between laughter and healthy function of blood vessels was first reported in 2005 by researchers at the University of Maryland Medical Center with the fact that laughter causes the dilatation of the inner lining of blood vessels, the endothelium, and increases blood flow. Drs. Michael Miller (University of Maryland) and William Fry (Stanford) theorize that beta-endorphin-like compounds released by the hypothalamus activate receptors on the endothelial surface to release nitric oxide, thereby resulting in dilation of vessels. Other cardioprotective properties of nitric oxide include reduction of inflammation and decreased platelet aggregation. 

Laughter has various proven beneficial biochemical effects. It has been shown to lead to reductions in stress hormones such ascortisol and epinephrine. When laughing, the brain releases endorphins that can relieve some physical pain.Laughter also boosts the number of antibody-producing cells and enhances the effectiveness of T-cells, leading to a stronger immune system.A 2000 study found that people with heart disease were 40 percent less likely to laugh and be able to recognize humour in a variety of situations, compared to people of the same age without heart disease. 

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