How often do we write about touch? A gentle stroke, a slap, a hug, a crush? Often.

But what's the science behind it? Why do we feel the way we do?

In his book, 'Touch - The science of the sense that makes us Human', David Linden goes into fascinating detail about how we feel, both physically and mentally.

I won't go into the fine detail (mostly because I can't remember it, partly because it is complex), but there are several types of cells, nerves and chemicals that cause our reactions.

Some 'touch' signals travel relatively quickly, others more slowly, which is why we feel some things quicker than others. He gives one example of a reaction in a giant to hot water: If your head lay in New England and your Feet in South Africa, the sensation of your toes being bitten by a fish on Monday, would reach your brain by Wednesday, and the brain's signal of reaction would reach your toes by Saturday.

The larger you are the longer it takes to feel things.

He also writes about the science that shows our mental feelings and our sense of touch are intimately linked. It's why soldiers can run about even though they're wounded, and why the fear of an injection heightens the pain. It's also why being mentally abused 'hurts'.

There are many other facets covered, a fair bit in dense science, but I recommend it if you want to really understand the sense of touch.