The obvious response to your child asking “why do we laugh when tickled?” is to say, “I don’t know, let’s do an experiment”. Give them a massive tickle while continuously asking them, “why are you laughing?”. Keep going until they have provided you with an acceptable theory.

OK, that might not actually get them any closer to an answer. But it would be a good laugh. The truth is that the reason we laugh and why we laugh when tickled are problems that have perplexed some of humanity’s greatest thinkers for thousands of years. It still largely remains a mystery. Which is good, it would be boring if we’d discovered everything.

The funny thing about laughter is that it rarely happens because of something funny. We laugh at unfunny stuff all the time. Especially when we are with people we like. We laugh to strengthen social bonds and we laugh when we feel awkward. Laughter is one of the first types of communication we learn. But if laughter is a signal of enjoyment why do we try to escape from being tickled and why do about a third of people say they don’t enjoy it?

When we are tickled it sends signals to different areas of the brain, areas that sense pressure, areas to do with pleasure, areas to do with pain and areas to do with the fight or flight response. This unusual mixture of pleasure, fear and pain going on in the brain might explain the bizarre reaction we have to being tickled. The goings on in the brain also help explain why we can’t tickle ourselves. One part of your brain tells the others that the tickle is coming so the response is greatly reduced.

We aren’t the only species to experience this. The other great apes laugh when tickled and so do rats. Yes, scientists did tickle rats to see what would happen. Here, and maybe with us a little too, it seems to be to do with showing submission to an aggressor and diffusing a potentially unpleasant situation. But tickling also happens between parents and children, siblings, couples and close friends in which it is viewed as a pleasant bonding experience and the laughter is an obvious signal of enjoyment.

A weird theory on tickling is that it is a way for parents to teach their children combat maneuvers. Seriously, people have suggested that! The idea is that when being tickled you are learning how to protect your vulnerable areas and evade an attacker. Could the laughter be a a way of making important survival training enjoyable? We laugh when we’re enjoying ourselves, but we also we enjoy ourselves more when we are laughing.

It’s very difficult to explain why we laugh during an experience that we are also trying to get away from. Roughly equal numbers of people enjoy tickling, dislike tickling or are neutral towards it. It could be related to our more dangerous and violent ancestry or it could be more about promoting family bonds. We just don’t know – a lot more tickling needs to be done to unravel this mystery.

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