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January 29, 2008

The truth about laughter

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[Transcript]

Everybody laughs. But why? Yes, we laugh at jokes, and when we’re having fun, but people also laugh when they are scared, nervous or embarrassed.  But now, Michael Owren, an associate professor in the Department of Psychology at Georgia State University, may have discovered the truth about why humans laugh.

OWREN: The normal interpretation of laughter is that it functions to convey to another person what state you’re in - what emotional state you’re in – specifically, that you are in a positive emotional state. (length: 0:12)

But, by comparing recorded human laughter to recordings of what Owren calls the “non-linguistic vocalizations of several species of non-human primates” (AKA monkey sounds to us non-scientists), Owren has finally unearthed the roots of laughter production.

OWREN: Human laughter resembles these primate calls in being strongly biologically grounded.  The earliest - and we think still most prevalent use of these non-linguistic vocalizations - is to induce an emotional response in your listener. (length: 0:16)

And, the emotional responses induced by these vocalizations can be so strong that they will often trigger an innate learning process, similar to that discovered in the famous experiment conducted by Ivan Pavlov where he conditioned dogs to salivate when they heard the ring of a bell.

OWREN: So, if you are a dominant monkey and you approach a subordinate in order to take away whatever it found, the resources it’s utilizing, food, or water, or even a nice place to sit in the sun, and you produce a threat call just before you chase it away, then the next time you approach that animal, and you produce that threat call, the animal will experience, the listener will experience a learned fear response. (length: 0:23)

Laughter, Owren says, engages the same kind of associative learning as the type induced in a subordinate animal by a dominant one.

OWREN: The interpretation that I’ve made about human laughter is that in human evolution, laughter changed, because by making it more voiced - ha-ha-ha - it became a more individually distinctive sound, and became a vehicle of mutual positive associative learning in individuals who genuinely liked each other.

The idea being that if you produce a vocalization when you are in a positive state, and you are more often than not in a positive state when you’re with another particular individual because you like them, the other individual, if they’re also in a positive state, meaning they actually like you, then they will associate your laughter sounds with their own positive state. If this happens consistently because two people really do genuinely like each other, then there will be an increasing positive feedback loop engaged, whereby the emotional stance between the two individuals will become increasingly positive. (length: 1:01)

As Owren sees it, this laughter response may have even played an important role in the evolution of the species.

OWREN: Human evolution, in particular put a premium on cooperative behavior among unrelated individuals.  Laughter is actually a mechanism of fostering and maintaining positive relationships among individuals. So, there the argument is that the reason we laugh when we’re nervous or embarrassed or facing a social challenge, is that in the face of that social challenge you can essentially recruit your friend by inducing a little positive response in that individual toward you, to help promote common action. (length: 0:33)

For Georgia State University RadioLine, I’m Andrew Flick.