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How Many Senses Are There?

How many times have you heard somebody say “It’s almost like he has a sixth sense!” or something to that effect. And you’ve undoubtedly seen, or at least heard of, the movie “The Sixth Sense.”

For many years, I’ve been bothered that that phrase. We were probably all taught in primary school that there are “five senses: sight, hearing, touch, smell, and taste.” And, although it’s forgivable that young children just accept what they’re taught, as adults, we should really know better. In fact, I can instantly identify at least one more sense that you have — temperature. Have you ever placed your hand inside a heated oven or over a burner on the stove (without actually touching anything)? Did you feel the heat? How about sticking your hand into the freezer without touching anything? Did it feel cold? Of course. And there is a sixth sense that we all possess. And the nerves used to transmit that temperature information to your brain are different from the nerves that transmit the sense of touch to your brain.

Here’s a seventh sense that you undoubtedly possess: Have you ever closed your eyes while standing and checked whether you’re able to detect whether you’re standing straight up or leaning over? That’s your sense of balance in play. It is, of course, created by the orientation and movement of fluid in your inner ears and the effect of those on the cilia (tiny hairs) in there, but it’s not the same as a sense of touch.

When we get away from purely human questions, we find even more senses than we might think. Sharks — as anybody who’s ever watched “Shark Week” on cable television will be aware — have a line of sense organs down their sides that can detect very tiny electrical impulses from the muscles of fish swimming nearby. That’s eight senses, so far. Many species of fish have a slightly different line of sense organs down their sides that can detect very subtle differences in pressure, the kind of difference that would be caused by a predator swimming rapidly towards them. And we’re up to nine senses.

Many bird species, numerous fish species, some amphibians, and probably others can detect the earth’s magnetic field and can navigate using that field the same way a ship’s captain navigates using the ship’s compass. There’s the tenth sense.

Many bird species can “see” the polarization of light and use that for navigation, too. This isn’t the same as our sense of sight, which detects light vs darkness, edges of objects, and color. It’s different and depends on entirely different kinds of receptors in the eye. We could quibble about whether this represents another sense or not, but I think it does…and that makes eleven senses.

I’m pretty sure that I haven’t remembered everything that can be reasonably considered to be another sense, but it’s a decent start in demonstrating that “the five senses” are little more than a myth. If you can think of additional senses that exist in the animal kingdom — and especially in humans — please comment on this entry and let the rest of us know what it is. Oh, and plants have still other senses that I haven’t mentioned herein, but please feel free to mention them yourself!

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