Back in kindergarten we were all taught that there are five senses: sight, hearing, touch,
taste, and smell.
Aristotle defined these in his book De Anima.
He then wrote: “One might be confident that there is not another sense beside the
five” and we’ve been listing them this way ever since, but...
Who’s to say an old greek was right?
Our ability to “sense” is incredibly complex.
When Aristotle came up with his definitive list, he linked them to visible
"sense organs."
But modern neuroscience recognizes that there's more to it than that.
If you close your eyes and put your finger near to your forehead – don’t touch it.
How do you know where your finger is?
It’s because you have position sense – or proprioception.
That’s Bruce Durie, a Scottish genealogist and author who wrote about sensory perception.
You can open your eyes now.
If you get up and walk around.
Do you trip over your own feet?
Hopefully not.
Your sense of sight prevents you from walking into a wall, but proprioception tells your
brain where your feet are, so you can walk without falling over yourself.
And this is different from just feeling the ground under your feet.
Scientists believe this sense works with receptors in your joints, ligaments, and muscles to
give you an awareness of your body.
It's also why your little league coach told you to “keep your eye on the ball.”
You didn’t need to watch where your hand was in order to catch it.
It doesn’t stop there.
There are actually some pretty extensive lists of “other” senses that vary depending
on how you define them.
By their popular definition, senses are restricted to five sensory organs.
But what about organs that didn’t make the cut?
There are two sensory organs in your ear alone and they’re responsible for very different
things.
One picks up sound waves for your sense of hearing, and the other maintains balance or
equilibrioception.
We can stay upright because there’s a vestibular system inside our inner ears.
It’s made up of fluid-filled semicircular canals and small hairs that pick up movements.
The brain combines signals from the vestibular system with other senses to maintain balance.
Try standing on one leg.
Easy, right?
Now shut your eyes.
It’s hard to do that with your eyes closed – at least without practice.
That’s because vision makes it easier to balance as it clarifies the orientation of
the world around you.
This partial reliance on vision is also why some people get motion sickness – when the
movement you see around you doesn’t match the signals your vestibular system is sending to your
brain, you get disoriented.
Organs aside, the list of senses really starts to expand when you define them based on receptors
in the body.
We’d arguably have to list thousands based on smell alone.
Or we’d create subcategories like we already have for taste based on an outdated taste map.
Touch can be broken down into categories too.
When you hold your hand over a hot stove, you feel heat without touching it.
That’s thermoception – it takes an entirely different group of receptors in your skin
to recognize changes in temperature.
We can also separate things like pressure, and pain.
These are different sensations based on different receptors that send signals to a different
part of your brain.
Listing just 5 senses means we’re leaving out a lot of things that actually keep us
alive and functioning on a daily basis. And don’t even get me started on the senses
we don’t have.
So this begs the question: is teaching five senses really the best way?
It’s just an easy shorthand.
I think the thing about the other five – the classic ones – and they don’t only work that way it’s how
we tend to talk about them – it’s about the outside world.”
When we’re young, learning these five senses is a really simple way to make sense of the
world around us.
These senses are based on external stimuli.
And because we have visible organs to link them to, they’re easy to test in a classroom.
We can touch objects, hear music.
See the classroom.
Smell a flower and taste lunch.
But what happens when we feel hot or cold in a room or if we lose balance and fall over?
These senses are hard to ignore but they can’t be classified as the ones we learn.
We don’t have a lot of conscious awareness of how complicated our physical bodies are
when they move about the world and the processing involved in that.
Because as soon as you do start to think about that then you have to start thinking about
these issues around sensation within the body.
Learning five basic senses might be the right place to start.
But next time you stub your toe -- think about that sensation -- it's one of the many senses
your kindergarten teacher never told you about.