Sixth to ninth senses

The human senses: sight, hearing, smell, touch, taste. Also balance, pain, proprioception, and interoception.

Thomas Bartholin / Public domain

Our brains get data from the world, and our senses are the sole pathway to the brain. Most people know about the five traditional senses: sight via the eyes, hearing via the ears, smell via the nose, touch via the skin, and taste via the tongue (that’s a gross oversimplification in itself, by the way; the senses are a complex network of organs, bones, neurons, and receptor cells). Extra-sensory perception is the fictional sixth sense on top of all those, but in fact humans have many more actual senses than the traditional five.

Our sense of balance – the vestibular system – tells us whether we’re in equilibrium or not, and whether we’re in motion or not. We have the inner ear to thank for that one. The sense of pain – nociception – is nerve or tissue damage felt in the skin, joints, bones, and internal organs. These aren’t just extensions of the five senses, but separate systems that give us data about the world.

Proprioception is one of my favourites: our internal sense of where all our body parts are. It’s really useful when we’re walking or reaching for something, less so when a limb is amputated and we get a leftover proprioceptive sense that it’s still there. In fact, there are heaps of other senses about our internal body state, grouped under the name interoception. Hunger, of course; internal chemical senses that tell our brains about thirst, and brain oxygen / CO2 levels; stretch senses that tell us when our lungs, stomach, bladder, or bowels are full; and many others. One thing’s for sure: there are a lot of candidates for that sixth sense.

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