Why our eyes twitch and 5 other probable explanations for strange involuntary body behaviors

Samantha Lee/Business Insider

Annoying eye twitches that make us feel self-conscious. Sleep twitches that refuse to let us sleep. Pins and needles that are just straight-up weird.

We like to think that we're in complete control of our bodies and that we understand them best. After all, every nook and cranny of the human body has been observed and studied for years — we must be experts by now, right?

Wrong.

A good portion of what goes on within us and why it happens remains a mystery and is often subject to debate.

Here are six strange involuntary bodily behaviors and their probable explanations:

Yawning

We yawn when we're tired. We yawn when we're bored. Yawns are contagious.

But despite how often we do it, scientists aren't sure why we yawn. One idea, outlined in a 2014 study, is that yawning helps regulate our brain and body temperature. Our brains use more energy than any other human organ, which increases its tendency to heat up. When we stretch our jaws to yawn, blood flow is increased to the skull and, as we inhale at the same time, the air helps cool down the blood as it flows to our brains.

This suggestion could also help explain why we yawn more as we get ready for bed or while we are getting up in the morning — our body temperatures are at their highest points during these times, and yawning helps us cool down.

Sources: BBC, National Center for Biotechnology, Smithsonian

Hiccups

Hiccups are repetitive and involuntary spasms of your diaphragm, a muscle located below your lungs that regulates your breathing. It contracts when you inhale and relaxes as you exhale. When the diaphragm falls out of its normalized rhythm, you get the hiccups (medical term: singultus).

Each contraction of the diaphragm causes the larynx and vocal cords to close, resulting in a rush of air into the lungs as you gasp or make the well-known "hic" of a hiccup.

Hiccups can be caused by overeating, eating or drinking too quickly, eating spicy food (which can irritate the lungs and stomach), swallowing too much air, and drinking carbonated beverages (which can irritate the nerves in our esophagus).

Sources: BBC, Healthline

Pins and needles

If you've ever crossed your legs for too long, you know the feeling: a numbing, prickly, burning sensation. That pins-and-needles feeling is caused by extra pressure being placed on a nerve (medical term: paresthesia).

The pressure reduces the blood supply that normally gets sent to a given area and prevents nerves from sending the right signals to your brain. Once the pressure is lifted, the nerves can work properly again — though they are misfiring as they get back to normal.

Long-term pins and needles may be an indication of a wide variety of other health conditions like diabetes, carpal tunnel syndrome, or traumatic nerve damage.

Sources: Live Science, National Institute of Neurological Disorders and Stroke, Better Health Channel, NHS Choices