The sound of laughter can reveal a relationship status, a new research has suggested.

Laughter has been known to have many health benefits, such as improving short term memory in older adults by delaying cognitive decline, but its social significance in relation to human cooperation is a topic rarely touched upon.

A study conducted by researchers from University of California, Los Angeles revealed that the sound of laughter varies depending on the existing relationship a person has with another individual, which means that your laughter will sound differently if you are with your friends compared to when you are with a stranger. Laughter has social implications that may define how humans have evolved.

Laughter between friends has minor pitch fluctuations and they tend to be longer, louder, and faster, according to Greg Bryant, lead researcher and professor of communication studies at the university.

In the study, 966 volunteers from 24 varying cultural backgrounds were asked to listen to 48 short audio clips of two people laughing. The recordings included laughter from two people who are either friends or newly acquainted. They also included laughter from either two males or two females, as well as from a male and a female.

After listening to the said recordings, the volunteers were asked to identify if the two individuals in the recording are friends or not.

The study findings showed that participants were able to correctly identify the sets 61 percent of the time. Researchers also noted that study participants have an 83 percent accuracy rate when the recording is of two female friends compared to 44 percent when they listened to two strangers.

"People from around the world assume that when two females are laughing together, they are friends," Bryant observed.

Since the study involved participants with different cultural backgrounds, Bryant said their study showed that vocal emotions can be universally understood. Hence, laughter allows us to socially communicate.

Bryant and his team concluded that the study findings also provide an insight as to how laughter has contributed to the concept of cooperation. He said social alliances are important for humans.

"If laughter helps people accomplish that, it has likely played a role in social communication leading to cooperative interactions," Bryant explained.

Robert R. Provine, a neuroscientist from University of Maryland who was not involved in the study, commented that laughter is indeed a powerful tool.

"Laughter may be a simple behavior, but it's also a powerful tool that provides insight into more complicated and difficult vocalizations, like speech and language," Provine said.

The study was published in Proceedings of the National Academy of Sciences.

You can try to listen to the recordings below:

Photo: Joshua Kehn | Flickr