Study on flavors of laughter

Georgia State University research presented at 2nd Pan-American/Iberian Meeting on Acoustics

Most scientific research on laughter is based on recordings of people pretending to laugh. But for Michael Owren of Georgia State University in Atlanta, this false laughter -- the sound of a canned sit-com laugh track -- is a pale imitation of the real thing. He studies the full vocabulary of chortles, giggles, guffaws we all use in everyday situations.

By recording people's laughter as they watch funny movies and playing these sounds back to listeners, he's trying to develop a better understanding of why laughter comes in so many flavors -- and how our brains respond to all of these different sounds.

"We don't know a lot about laughter produced in different emotional states -- in amusement,  embarrassment, schadenfreude, etc.," said Owren, who will present his latest experiment at upcoming 2nd Pan-American/Iberian Meeting on Acoustics in Cancun, Mexico. "There have been some claims, but they've been based on simulated laughter, a stereotype of real laughter."

Owren asked participants in his study to watch funny film clips selected from a variety of movies and recorded their natural laughs. By analyzing the spectrograms (the graphed images of the sound) of every laugh, Owren separated them into different categories. He then played the laughs back to listeners and asked them to rate how positive the sounds made them feel.

Full-voiced laughs made with the mouth open -- the classic "ha ha" that engages the vocal cords -- had a much bigger impact on listeners than closed-mouthed voiceless laughs -- which sound low and breathy. Even people who tended to laugh without using their vocal cords found the voiced, song-like laughter more appealing.

Why do we prefer one style of laugh to another? Owren suspects that this preference may be a clue that our responses to expressions of emotions aren't just hardwired into our brains. After all, both sounds are just sounds.  He thinks our responses to them are shaped over time as we learn to associate certain sounds with certain experiences.  

"Laughter is designed to convey the emotion of the person laughing," said Owren. "If this were just an innate thing, there shouldn't be a difference between these two types of laughter, both of which convey positive emotion."

Owren's experiment is part of a body of basic research breaking down the complexities of the human voice. This research could find potential applications one day in computer speech processing technologies that seek to understand not only the content of a person's words, but also their emotional meaning. It could also be useful for researchers who are trying to create more realistic speech-synthesizing technologies better able to mimic how people communicate.

The poster "Voiced laughter elicits more positive emotion in listeners when produced with the mouth open than closed" will be presented on Friday, November 19.