I used to think we had five senses — sight, hearing, taste, smell and touch. And I used to think I knew how they worked. Using specialised instruments, such as eyes, ears and fingertips, they gave us information about the outside world. I imagined that the eye saw things, and then told the brain what those things looked like. I imagined that the fingertips touched things, and then told the brain what those things felt like. But now, every time I look at a book on neuroscience, I see that this nice cosy picture is absolutely wrong.
Before I continue with this line of thought, let me say that this book is about the sense of touch, it’s by a professor of neuroscience at the Johns Hopkins School of Medicine, and it’s excellent. It will tell you why footballers hug each other when a goal is scored, why they are like vampire bats in this respect, and why some people like being the recipients of anal sex while others don’t. David Linden tells us all of this with exactly the right degree of scientific dryness.
Getting back to what I was saying before: it’s not quite true to say that when you touch something, the nerve endings in your fingertips tell your brain what it is. It’s more like when you touch something, your brain tells your fingertips what it should feel like. As Linden puts it, ‘Context is key in sensory experience.’ One example he uses is the caress of a lover versus that of a doctor —one feels great, the other not so great. That’s because, in each case, your brain is telling your body how to feel about the caress. Similarly, if you play the violin for thousands of hours, your fingers will begin to feel the contours of the strings in much more detail.