No threat looms quite so large as that of the Tickle Monster. You never know when it will strike, and it takes only moments to reduce you to a collapsed pile of giggles. But why is the Tickle Monster so effective? Why are certain spots more ticklish than others?
The existence of tickle spots highlights a design feature of skin—not all areas are the same. Different parts of your skin sport wildly different sensitivities to the world around you.
These differences come from varying “sensory neuron distributions.” That’s science for saying some parts of your skin have more nerve endings than others. Your fingertips hold more nerve endings than your palms, which have more than your forearms, and on it goes.
Have you ever noticed that your mom checks your temperature with her cheek instead of the back of her hand? Or that when you check the temperature of a pool with your foot it can feel different than when you dunk your head in?
The more nerve endings packed into any given patch of skin, the more sensitive it is to temperature, pressure, and vibrations. While the skin on the back of your leg could feel bumps on a page, your fingertips distinguish individual letters of the Braille alphabet.
God designed our brains to process a lot of information within limited space. The more nerves in a patch of skin, the bigger the brain area needed to interpret their signals. Furthermore, if all areas were as sensitive as the fingertips, the constant flood of information would overwhelm us. So our Creator prioritized, making our fingertips, hands, and face more sensitive than our upper arms, back, and legs.
In addition to targeted distribution of sensory nerves, our brain has the remarkable ability to block overstimulation, as well. This leads to some interesting effects. For example, can you feel your socks right now? Well, now that they’re on your mind, you probably can. But after you got dressed this morning, you likely forgot how your clothes feel. If you think about it, you can feel their texture, but you have to focus on it. Your brain filters out information it deems unimportant—like feeling your clothes—so you can focus on more important matters.
The reverse is also true. Our brains can “feel” things that aren’t there anymore. People who have lost an arm or a leg often experience phantom limb pains. This happens when their brain tells them that their arm, or any other missing body part, hurts or itches. Your brain is so used to receiving constant “background” signals from your entire body that when something gets removed, it has trouble sorting out why that information is missing.
God carefully created us, giving close attention to all our parts, even our skin (Job 10:11). It may all look the same, but each part of our skin has different strengths for different jobs, from our forehead to our feet, from the right side to the left. Every part of you is beautiful and unique to accomplish God’s ordained purpose, just like you.
Test It Yourself . . .
You can test how sensory neurons are unequally distributed on your body with the help of a friend and some common household items. Simply bend a paperclip into a “U” shape and grab a ruler that measures millimeters to conduct your own personalized two-point discrimination test.
Close your eyes and have your friend gently poke the skin on the back of your hand with the ends of the paperclip. How close together can you put the ends and still feel two separate points? Measure that distance and compare it to the sensitivity of your fingertips, arms, forehead, calves, and back. Perform the same test on your friend and compare results.
What areas of your skin are the most sensitive? The least? Is your right side more or less sensitive than your left?