London: What has been known to us all is now proven by research. Apparently genuine laughter is the best medicine according to a report published in current Quarterly Review of Biology.

The study, which explains how laughter has evolved over the past seven million years, found that there are two types of laughter – genuine and artificial. The first type is spontaneous and stimulus-driven, while the second, is strategic and, at times, downright cruel, also nicknamed 'the dark side of laughter,'

'One type of laughter arises spontaneously from the perception of a certain class of events, while the other is used strategically in interaction to influence others or modulate one's own physiology,' said Matthew Gervais, lead author of the study.

The researchers found that genuine laughter is innate and mirrors ape play-panting, which arose around seven million years ago. They believe human laughter sounds more like a wild primate call than language.

Between four and two million years ago, this laughter evolved as a reaction to non-serious social incongruity, such as when one human ancestor would hear another loudly pass gas while the individuals felt safe and were playing.

Around two million years ago our ancestors evolved the ability to willfully control facial expressions. It was not long before fake smiles led to fake laughter, which can be used for emphasis in conversations, to relieve fear, to shame others, and for many other purposes.

Genuine laughter first emerges involuntarily in babies from the middle part of the brain and brainstem areas. Fake laughter originates toward the front of the brain, and seems to develop more as a person ages.

'One of the hallmarks of the human brain is the extent to which cortical, cognitive, namely prefrontal areas can influence and control behavior, and these areas are the last to develop and perhaps never cease doing so,' said Gervais.

Control over laughter may not be such a bad thing, since it could prevent someone from laughing out loud at inappropriate times, which may vary depending on the culture.

'What I call 'laugh-speak,' a hybrid of speaking and laughing, is under more voluntary control, and is used by talk-show hosts and others to buffer an uncomfortable point,' said Provine, who is a psychology professor at the University of Maryland Baltimore County.

The researchers said that people who spontaneously laugh more are genetically superior to those who hardly ever chuckle. They could be healthier, happier, more attractive or more cooperative.

(Source: ANI)