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What makes you laugh and cry?

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Professor Sophie Scott explains her latest experiment at the museum, exploring the science behind laughter. 

Last year, we had a mouse somewhere in our flat, and we were all stressing out about it a bit. I was at home on my own when I thought I felt something running over my foot. It was a hair pin falling out of my hair, but before I had realized this, I screamed out loud. I screamed loud enough and long enough for me to have time to think things like “Why am I screaming?”, “I am not afraid of mice” and “Pretty sure that was a hairpin”.

The really interesting part of the mouse incident was that my scream was involuntary – I really did not mean to do this (there’s a great example here). Involuntary vocalizations are produced via a neural system we share with other mammals, but a separate network in the brain controls speech. This speech network, which evolved much later, allows us to produce the complex movements which underlie speech and song and to do so voluntarily – we choose when to speak.

A spectrogram of the sentence “the house had nine rooms”. The horizontal axis is time, the vertical axis is frequency. This shows the acoustic complexity of speech.

A spectrogram of the sentence “the house had nine rooms”. The horizontal axis is time, the vertical axis is frequency. This shows the acoustic complexity of speech. Credit: Sophie Scott

The older, involuntary system is associated with emotional vocalizations in humans – like my screaming or a cry of surprise. These emotional sounds (such as crying, screaming, laughing) are more like animal calls than they are like speech.

This shows laughter. Note how much less complex the sound is. Credit: Sophie Scott.

This shows laughter. The sound is much less complex than speech. Credit: Sophie Scott.

This shows a spectrogram of a cat meowing. As with the laughter, we can see spectral structure but this does not vary much over time. Credit: Sophie Scott.

This shows a spectrogram of a cat meowing. As with the laughter, we can see spectral structure but this does not vary much over time. Credit: Sophie Scott.

Our more recent voluntary system is associated with speech and song (and other vocal skills such as beatboxing). If this system is damaged, for example, due to a stroke, people can be left with aphasia – a persistent problem with talking. They very often can still make emotional noises, such as laughing, suggesting that the stroke has not damaged this older pathway.

For my research, we are studying what it means to make voluntary and involuntary vocalizations – for example, laughter is used a great deal during conversational speech. Even babies use emotional expressions like crying and laughter in extremely sophisticated ways.

This all suggests that there may be both voluntary and involuntary kinds of emotional sounds. Are laughs and sobs produced in a voluntary or an involuntary fashion really different? How do they sound to us? How does this change as we age?

Laughter experiment at the Science Museum. Credit: Science Museum.

Laughter experiment at the Science Museum. Credit: Science Museum.

To help discover the answers to these questions, we are running an experiment at the Science Museum. We ask people to listen to ‘real’ and ‘posed’ laughter and sobbing sounds to find out how they sound to people. So if you are interested in knowing anything more about voices and emotion do please come along and take part in our research – we promise not to make you scream.

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  1. Rachel

    And how come children are so good at pretending to laugh or cry? Or is that just mine? Or am I just conditioned to respond to my own children’s joy or sadness and I am therefore more susceptible to their laughs or cries even if they are forced?

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