Even though subjects like religion, who you're voting for, or what you think about deep dish pizza can divide us, every human can find common ground in the sensation of getting hard nipples. It just happens, often thanks to things like cold weather or sexual arousal. But why? What's the, uh, point? A new video from the folks over at DNews on YouTube offers a helpful explanation.
According to the video, the question of how your nipples get hard might be a little easier to explain than why your nipples get hard. Turns out that scientists believe there are nerve cells that exist for the sole purpose of causing the muscles in your nipples to contract and become erect when your sympathetic nervous system (the thing that controls involuntary responses like fight or flight) activates the cells with a neurotransmitter called norepinephrine. In other words, getting hard nipples is just an involuntary response that involves signals from your brain.
As for why your nipples get hard, well, there are a few possible explanations. The first is that they're designed to get hard to assist with breastfeeding, which obviously makes a lot of sense. However, researchers are less clear as to why your nips tend to get stiff in sexual scenarios or when you're cold, but there are some suggestions that this has to do with the same reactions that cause your body's hair to stand up, among other possible explanations. It's also possible that your little "shirt tents" could also be a sign of arousal, according to the video.
For the full explanation, and even a segue into the topic of why men have nipples, check out the short but informative clip.