Why do we laugh when tickled?

15 April 2014

Question

My curiosity is about tickles. Why do we laugh (to an extent!) when tickled, and why can it be only done in certain areas of the body? Is there an evolutionary explanation for it? I understand cars purr when patted, is it by the same physiologic mechanism that this happens in humans?

Answer

Hannah - Tickling is a very, very serious topic, Chris. Scientists take it incredibly seriously. Recently actually, scientists studied 30 volunteers in an MRI scanner to try and get to the bottom of this tickling phenomena of why we find it so hilarious and so entertaining. It's something to do with us, not expecting it, something we're not predicting it is going to happen and we're not sure exactly how it's going to feel or how a person is going to be tickling us. So, people were scanned in an MRI scanner whilst they were being tickled or they were being told a joke and it turns out that both the rolandic operculum, an area of the brain that's involved in facial movements and emotional reactions lights up to both tickling and telling a joke. But then there's an extra area of the brain that lights up when people's feet are being tickled when their feet are poking out of the scanner and that's the hypothalamus which is interesting. Now, the hypothalamus is involved in regulating our feelings of hunger, tiredness and body temperature, and it's also involved in the flight or fight response. So, if you're scared, you might want to fight with someone or run away. And now, producer for the show Kate Lamble, if I threatened to tickle her and apparently, if her boyfriend does tickle her, she will literally thump the person that's tickling her. So that, she seems to definitely have her fight or flight reaction activated by tickling. So yeah, tickling seems to invoke these feelings in people and we're trying to understand. Scientists are trying to understand a little bit more about what happens in tickling. It seems to be an innate response laughing to tickling. So, new born babies, if they're tickled by a parent with a very straight face on, they will still start giggling and laughing away. So, it's something that we have evolved to do and we're still trying to understand it exactly.

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