We are taught that, as we stumble through the world, we have touch, taste, smell, hearing, and sight to guide us. It turns out that we have been underestimating ourselves. Scientists count between fourteen and twenty actual senses, most of which aren't taught in primary school. See what information you're really working with.
10. The sense of when you have to go to the bathroom.
It doesn't seem impressive, but trust me, you'd miss this if it were gone. Now is, however, a good enough time as any to discuss what makes a sense. Scientists, for example, don't make 'social discomfort' a sense even though that certainly as strong as this sense. In order to make something a sense, there has to be some organ, or set of organs, that are meant to sense that one specific thing. In this case, there are special sensors in the rectum and the bladder that sense their stretch and communicate the need to urinate to the brain.
9. The sense of hunger and thirst
This wouldn't be as socially embarrassing as freely going to the bathroom all the time, but we do have special receptors that tell us when we are hungry and when we are thirsty. Technically these count as two different senses, though in some animals, like mammals that live underwater, they are one. If dolphins drink fresh water, they stop eating. Since they get their fluids from their food, they can't tell the difference between hunger and thirst.
8. The sense of itchiness
Aside from all the other nerves in the skin, there are some that just pick up on itchiness. These have to be the most easily fooled nerves in the body. I bet you're itching all over right now. And now that I've mentioned it, you're itching more. That's right. I control you.
7. The sense of pressure
We know when nothing is touching us, when something is barely touching us, and when something touches us harder. We know this even if we don't feel pain. Pressure sense keeps us from bruising like spoiled fruit on a daily basis. It's important enough that even creatures with exoskeletons often develop pressure sensors, to guide them through the world and keep it from crushing them.
6. The sense of temperature
And thermoception, our sense of heat, is what keeps us from cooking ourselves like a fruit pie, or just quietly freezing to death while watching the stars. There are specialized nerves in the skin that pick up hot and cold independent of everything else.
5. The sense of where your body is compared to itself
A good demonstration of proprioception means the difference between a curt goodnight and a ticket for drunk driving. It allows us to watch tv while typing away at a computer, or getting a set of house keys out of our pocket, or brushing our teeth. It gives us a sense of where our body is in relation to itself. So it allows us to reach down into a bag of popcorn resting on our lap, fish around for a handful, and bring it to our mouths, all while still watching a movie. Since theaters make most of their money on the snacks, this is clearly the thing that keeps the movie business alive.
4. The sense of where you are in the world
This is another sense that deserts a lot of people who then get locked up in the drunk tank. The fluid-filled inner ear allows us to figure out whether we're standing straight or about to take a spill onto the sidewalk.
3. The sense of movement
Some of us have been sitting on a train that was standing still, and experienced an intense rush of vertigo when we turned to the window to see another train rolling by. The other, moving, train filled our vision and made it seem like maybe it was standing still and we were moving. Our eyes clashed with what our inner ears, which monitor this sense, were telling us, and we got a sense of disorientation while our brains tried to figure it out.
2. The sense of time
When we stumble out of the movie theater, after having watched a revival screening of Gone With the Wind, we don't get surprised that we've been in there hours instead of minutes. What's more, even though we've seen Scarlett go through the civil war, build up a successful lumber business, conceive, birth, and raise a child, and yell "Rhett" and "Tara" about a thousand times, we don't assume we've been in the theater for years. Our temporal sense does fail us, but even distracted by images and wooed by an epic narrative, we keep a fairly good sense of how much time we have.
1. The sense of pain
Nociception is perhaps the least appreciated sense. It's our sense of pain. Getting rid of it would get rid of a lot of the problems of the world, and eliminate some of the most intensely unpleasant parts of life. It would necessitate a trade-off, though. Replacing that intensity would be a long, slow grind. Instead of intense moments of agony that would last a few seconds before we pulled away or did what we could to eliminate the cause of the pain, there would be the constant physical therapy needed to functionally heal from breaks, sprains, burns, strained muscles, cuts, and bruises. Without pain, there is no sense to tell people to pull away from behaviors that physically damaged them. In ancient cultures, pain probably kept people from dying. In the modern world, where the stakes are lower, it's more of a time-saver. One brief moment of agony keeps us from doing damage that would need months or years to heal.
Via How Stuff Works, Harvard, and WiseGeek.