It's puzzling, isn't it? No matter where you try to tickle yourself, even on the soles  of your feet or under your arms, you just can't. To understand why, you need to know more about how your brain works. One of its main tasks is to try to make good guesses about what's going to happen next. While you're busy getting on with your life, walking downstairs or eating your breakfast, parts of your brain are always trying to predict the future. Remember when you first learned how to ride a bicycle? At first, it took a lot of concentration to keep the handlebars steady and push the pedals . But after a while, cycling became easy. Now you're not aware of the movements you make to keep the bike going. From experience, your brain knows exactly what to expect so your body rides the bike automatically. Your brain is predicting all the movements you need to make. You only have to think consciously about cycling if something changes---like if there's a strong wind or you get a flat tyre. When something unexpected happens like this, your brain is forced to change its predictions about what will happen next. If it does its job well, you'll adjust to the strong wind, leaning your body so you don't fall. Why is it so important for our brains to predict what will happen next? It helps us make fewer mistakes and can even save our lives. For example, when a chief fireman sees a fire, he immediately makes decisions about how best to position his men. His past experiences help him foresee what might happen and choose the best plan for fighting the fire. His brain can instantly predict how different plans would work out, and he can _ any bad or dangerous plans without putting his men at risk in real life. So how does all this answer your question about tickling? Because your brain is always predicting your own actions, and how your body will feel as a result, you cannot tickle yourself. Other people can tickle you because they can surprise you. You can't predict what their tickling actions will be. Our brains cannot predict what will happen when we  _  .
walk down the stairs eat our breakfast suddenly lose our balance and fall ride a bike