91色情片

Why is pain so painful? After all, it is only nerve impulses sent to our brains like many others.

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Neil Frizzo Newcastle, New South Wales, Australia

Pain is so painful because the consequences of it not being so are worse.

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@PhilMorey8 via Twitter

The function of pain is to stop you doing stupid things twice. It has to hurt to make it work.

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Pat French Rockhurst, Shropshire, UK

The impulse sent by a nerve from the site of a trauma is indeed similar to the impulse from a sensor cell in the retina of the eye or the cochlea of the ear. It is how the brain interprets this input that produces an experience, be it colour, sound or pain.

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Herman D鈥橦ondt Sydney, New South Wales, Australia

The real issue here is that we never perceive reality: what we perceive is only the brain鈥檚 interpretation of nerve impulses. Nerves were 鈥渄esigned鈥� by evolution to tell animals what was happening inside and around the body. This happened long before there were any brains. There were just nerve signals. Some indicated a touch from another body that was to be avoided; others showed where light was, and that might need to be either sought or avoided. When animals evolved brains, a far greater range of responses became possible.

When a nerve signal arrives in the brain, it is processed by multiple layers of neurons. That processing is what interprets reality. This is easy to see when we look at an optical illusion like the Necker cube, where the processing is unable to decide what we are looking at, and keeps switching between two possible interpretations. It also means that nobody can tell you whether 鈥渞ed鈥� looks the same to them as it does to you. We just know to associate a particular set of nerve signals with the conscious experience that we call 鈥渞ed鈥�.

In the case of pain, evolution altered our brain to remind us that those signals should be avoided. It would be good, though, if we could switch them off once the pain has been recognised. Why keep reminding me that a burn can hurt, long after it happened?

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Tony Durham Brighton, UK

Pain, perhaps more than pleasure, drives reinforcement learning. It is the past experience of pain that keeps you out of trouble. The pain you feel when you stub your toe represents not only the immediate injury, but also the small but serious risk that you will die as a result. Evolution has decided that injuries have to hurt a lot, in order to give you the best chance of surviving, reproducing and bringing up children.

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