You’re reading the morning paper, or turning the page on your recipe, when suddenly you notice a little line of blood, and feel a disproportionate amount of pain.
Paper cuts are tiny, barely cuts at all, more like deep scratches. So why do they hurt so much?
Some areas of our bodies have more nerve cells than others, meaning that those areas are more sensitive to touch. A visual representation of this is seen in the cortical homunculus, a humanoid figure whose most sensitive body parts are the largest.
As you can see, his hands are huge! That’s because our hands are one of our most sensitive body parts, able to detect microscopic differences in surfaces.
With that many nerves it’s no surprise that any cuts on our fingers, even those done by paper, hurt like heck. It certainly doesn’t help that we use our hands all day long, so are prone to reopening the healing cut, or getting foreign substances into it.
Curious what parts of your body are the most sensitive? Try the two-point discrimination test! Have a friend take two pencils (dull ones!) and touch them to your back in different, far apart, places. Slowly bring those pencils closer together, and note the point at which you can only feel one pencil. Then repeat the experiment on other body parts.
Everyone is different, but the image below shows the approximate distances you begin to distinguish between the two pencils at on different body parts. Generally the lips, tongue and hands are the most sensitive, and the back and shins the least.