Proprioception

Close your eyes. Now, touch your nose.

That’s pretty easy to do, right? Our bodies have an innate ability to find various parts of themselves, with no need to see where anything is. This ability is called proprioception, and it’s sometimes thought of as another sense, just like hearing, seeing, or taste.

You’re thinking: wait a sec, isn’t that just what we think of as a sense of feel? I remember that senses were neatly divided up into five categories when I first learned about how we experience the world directly. Everything, it seemed, could fit into one of these groups.

Rock-solid certainty about numbers was big during the 80s. My personal perception—the message I received from school over 13 years of public education and somewhat more than four years of college—was that science had an awful lot figured out. It seemed as though we hairless apes had solved most of the mysteries of the way things worked, and we enjoyed touting our brilliance by proudly knowing some key numbers, like that there were 9 planets in the Solar System.

When Pluto was dropped as a planet in 2006, it was because the International Astronomical Union voted to reclassify it as a dwarf planet, based on tons of new evidence that forced scientists to reconsider how to define our planetary system. When a bigger rock with similar characteristics was discovered in 2005, this was enough to pause and take a fresh look.

Ultimately, Pluto is better classified as a dwarf planet for reasons we can get into some other time, but the point I want to make is that every kid had to learn that there were nine planets.

Equally emblazoned was the fact that there were five senses in the human body.

Every kid I knew learned that there was sight, hearing, touching, smelling, and tasting, and that was it. Those were the only ways any information got inside your skull from the outside, or so we were so certain.

Fortunately, we’re not committed to believing something for the rest of our lives just because we thought we were sure. If you’re sure something is lemonade but it turns out to be lava, you don’t actually have any obligation to drink it. So it goes for our “five senses.”

Proprioception isn’t the only sense like this, but it’s a really important one. Along with its close cousin, kinesthetic awareness, you can get a sense of where you are. Proprioception lets you know this when you’re sitting still, whereas kinesthesia describes the same phenomenon when you’re in motion.

Let’s turn back to that sense of feel again. Don’t you sort of feel where your limbs and other body parts are? Isn’t that the same sort of signal as when you reach out and touch something (or someone else)?

How about if you’re just sitting in your chair—could you tell if you were wearing corduroy or satin? I bet you could. Isn’t that the same as knowing where your parts are?

Not quite.

Proprioceptors (from Latin roots proprius and capio—something like “to grasp what is mine”) are embedded in your body in lots of different places. Inside of your muscles, you have little muscle spindles—tiny sensors that act like rulers, constantly measuring how long your muscle is at that particular moment.

Similarly, your tendons (they connect bones to muscle) have sensors right where they meet the muscles. Think about what happens to this connection if a muscle contracts. The tendon gets a little tug, right? That’s how you know when to let go of a heavy weight you’re trying to pick up. If something is so heavy that it’s going to rip your tendon from your muscle or bone, you will tend to drop that thing.

This isn’t a feeling like pain, but instead kind of a general awareness that you shouldn’t be doing this. You just kind of know when to let the heavy weight go.

Similarly, joint receptors operate the same way, telling you if your limb is bent, and whether it’s at a particular angle. If you’ve ever tested the limits of your own limbs, you may have found that something inside knows when a limb is at the breaking point.

This combination of things leads you to be able to know where you are, essentially.

This is nowhere more obvious than in the sport of Brazilian Jiu Jitsu, where submissions work the same whether you’re upside down or not. While you’re born with some innate sense of proprioception, you absolutely can improve this skill over time. With enough practice, you may be able to become many times more aware of your own body’s positioning than you were previously.

That’s where I notice proprioception the most, anyway. What about you? Do you have hobbies or activities where you’ve really noticed this awareness improving? Have you thought much about this type of sense before?