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Laughter is the biological reaction of humans to moments or occasions of humor: an outward expression of amusement. Laughter is subcategorised
into various groupings depending upon the extent and pitch of the laughter: giggles, chortles, chuckles, hoots, cackles, sniggers
and guffaws are all types of laughter. Smiling is a mild silent form of laughing. Some studies indicate that
laughter differs depending upon the gender of the laughing person: women tend to laugh in a more "sing-song" way, while men more
often grunt or snort. Babies start to laugh at about 4 months of age. Philosopher John Morreall theorises that human
laughter may have its biological origins as a kind of shared expression of relief at the passing of danger. The relaxation of
tension we feel after laughing may help inhibit the fight-or-flight response, making laughter a behavioral sign of trust in one's companions.
Laughter is a part of human behavior regulated by the brain. It helps humans clarify their intentions in social interaction and provides an emotional context to our
conversations. Laughter is used as a signal for being part of a group — it signals acceptance and positive
interactions.
On the other hand laughing at somebody is ridiculing him or
her.
Certain medical theories attribute improved health and well-being to laughter as it triggers the release of endorphins. A study demonstrated neuroendocrine and stress-related hormones decreased during episodes of laughter, which provides support for the claim that humor can relieve
stress.
Research has shown that parts of the limbic system are involved in
laughter. The limbic system is a primitive part of the brain that is involved in emotions
and helps us with basic functions necessary for survival. Two structures in the limbic system are involved in producing laughter:
the amygdala and the hippocampus.
Researchers frequently learn about how the brain functions by studying what happens when something goes wrong. People with
certain types of brain damage produce abnormal laughter. This is found most
often in people with pseudobulbar palsy, gelastic epilepsy, and to a lesser degree, with multiple sclerosis, ALS, and some brain tumors.
In most people, laughter can be induced by tickling, a phenomenon in itself.
Laughing gas is sometimes used as a painkiller.
The December 7, 1984 Journal of the
American Medical Association describes the
neurological causes of laughter as follow:
- "Although there is no known `laugh center' 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 centers concerned with respiration. Wilson considered the mechanism to be in the region of the
mesial thalamus, hypothalamus, and subthalamus. Kelly and co-workers, in turn, postulated that the tegmentum near the
periaqueductal gray contains the integrating mechanism for emotional expression. Thus, supranuclear pathways, including those
from the limbic system that Papez hypothesized to mediate emotional expressions such as laughter, probably come into synaptic
relation 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."
Laughter is not confined to humans. Chimpanzees show laughter-like behavior
in response to physical contact, such as wrestling, chasing, or tickling, and rat pups emit
short, high frequency, ultrasonic vocalizations during rough and tumble play, and when tickled. Rat pups "laugh" far more than
older rats.
See also
References
- Goel, V. & Dolan, R. J. The functional anatomy of humor: segregating cognitive and affective components. Nature
Neuroscience 4, 237 - 238 (2001).
- Bachorowski, J.-A., Smoski, M.J., & Owren, M.J. The acoustic features of human laughter. Journal of the
Acoustical Society of America, 110 (1581) 2001
- Fried, I., Wilson, C.L., MacDonald, K.A., and Behnke EJ. Electric current stimulates laughter. Nature, 391:650,
1998.
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