A joyful belly laugh is interpreted by the brain in a completely different way from a scornful titter or the giggle from someone being tickled, a group of scientists from Tübingen in south west Germany have found.
In experiments designed to eventually help patients with chronic anxiety disorders, the neuroscientists found that positive non-verbal communication, such as a joyful laugh, was processed by a different part of the brain from a negative, scornful snicker, they wrote in US science journal PLOS ONE this week.
Understanding laughing - one of the oldest forms of non-verbal communication also seen in rats and apes in the animal kingdom - could be key to helping patients with psychiatric disorders, who often are unable to correctly interpret non-verbal communication.
“Animals use it for example when they are playing catch games,“ said project head Dirk Wildgruber from Tübingen University. “It is used as a reward signal to raise the willingness of parents and siblings to play with the youngest animals – and prepare them for later tasks.“
Humans, on the other hand, have developed several different forms of laughter, each of which can have a complex series of meanings and intentions behind them.
"Laughing is a very strong signal in social interaction. If you are laughed at with joy you feel accepted. If you are the victim of scornful laughter, you feel shut out of the group," said Wildgruber.
In their experiments, Wildgruber and his team played volunteers various types of recorded laughter and measured how the sounds were interpreted in the brain.
They found that giggles generated when someone is being tickled stimulates areas of the brain responsible for interpreting complex acoustic signals.
Yet happy or scornful laughter stimulated completely separate brain regions usually tasked with guessing the intentions of others. From there, the laughter kick-starts connections with different parts of the brain depending on the tone - negative or positive.
"[Our findings are] really relevant for psychiatry patients," said Wildgruber. Many psychological illnesses such as anxiety, depression or schizophrenia are often exacerbated by a disturbance in the brain's ability to correctly interpret non-verbal communication, he said.
The next step will be to look into how people with psychological disturbances react to different laughter signals to find out which areas of the brain could be artificially stimulated to help them, said Wildgruber.