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Speaker 1: Welcome to brain Stuff from how stuff works dot com.

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Speaker 1: We're Smart Happens. I am Marshall Brain with today's question,

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Speaker 1: how do cats pur? Humans seem to be fascinated by

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Speaker 1: animals who can do things that we cannot. For example,

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Speaker 1: how stuff Works covers questions about camel humps, hawk vision,

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Speaker 1: dear night vision, fish gills, and so on, And so

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Speaker 1: it is with cats purring. Humans can't pur, so we're

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Speaker 1: interested in how cats can do it. It turns out

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Speaker 1: that domestic cats, some wild cats like pumas, and mountain

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Speaker 1: lions in general, any big cat that can't roar, and

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Speaker 1: even raccoons are all able to pur. Cats show happiness

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Speaker 1: by purring. They may also purr when they're startled or upset.

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Speaker 1: Humans happen to smile and laugh when we're happy, and

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Speaker 1: dogs why their tails, So it's not unusual for an

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Speaker 1: animal to have a physical reaction to happiness like this.

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Speaker 1: So how do cats pur? It turns out that cats

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Speaker 1: have special wiring. The wiring travels from the brain to

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Speaker 1: the muscles in their voice box, and this wiring is

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Speaker 1: able to vibrate the muscles, so they act as a

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Speaker 1: valve for air flowing past the voice box. The muscles

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Speaker 1: work both during inhalation and exhalation, and that creates the

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Speaker 1: impression that cats can pur continuously. The air passes through

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Speaker 1: the valve, which opens and closes rapidly to create that

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Speaker 1: purring sound. For more on this and thousands of other

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Speaker 1: topics because it how stuff works. Dot com