This has nothing to do with seeing dead people or being psychic. We've obviously got smell, taste, touch, hearing and sight. However, in addition to these five, our inner ear senses our body's orientation in space.

Somehow, we've learned that five is golden, and got stuck on that number.

The technical term for the "normal" sixth sense that mattbw describes is proprioception.

This is my highest-rated writeup? WTH?

The sense of equilibrium is part of a larger sense or set of senses known as kinesthetics.

The sense of kinesthetics, while often not regarded as a sense or as a form of intelligence, is in fact essential to everything that we do.

It involves many different kinds of intelligence:

  • the ability to understand and interact with dimensional shapes such that we are able to navigate successfully through a room.
  • as a sense of timing and coordination, fine-motor control and the manner in which both the whole body and its parts move, its deportment or dynamics.
  • apprehending the actions, feelings, or dynamic abilities of other people, without the medium of words.
Such things as Haragei (belly talk) are aspects of kinesthetics. The traditional Japanese arts provide extensive training in kinesthetics.

But then what about the third sense in sensei's above post, interpreting information without words (I'd call it empathy)? Though this relies on sight and sound, it really is a separate, internal sense. Some people are better at it than others, and some people are completely lacking in it (autistic people, for example). This sense develops from experience just as our other senses do, but this it takes stimulation from social interaction, instead of the environment. I think that can be classified as a sixth sense.

"Proprioception" is different from touch. Our tactile sense is achieved through the nerve endings in our skin and throughout our body (the most fun parts of our body are the ones that have the highest density of nerve endings ;-). Our sense of balance and orientation comes from a different organ: our inner ear. This is what allows us to know whether we are upright or prostrate, without opening our eyes. None of the "traditional five" senses gives us this information. Only our inner ear can tell us that.

This is why people with vertigo think that the room is constantly spinning. It's an inner ear thing. Also, when astronauts experience weightlessness, this sense becomes utterly useless. It takes some time to get used to being without this sense. Most astronauts vomit the first time they enter orbit.

So I would call proproiception/balance a sixth sense.

Proprioception, also known as our sixth sense, was the last of the senses to be investigated. In essense it is concerned with knowing where our body is in relation to itself. For example when you close your eyes and touch your nose proprioception is what guides your movements. Without it simple tasks such as scratching the back of your head becomes almost impossible.

In very rare cases it is possible to lose this sense - usually as a result of drugs. When this happens the patient feels as if they are not attached to their bodies, they are no longer behind their own eyes. They must relearn movements using their eyes for feedback. They also lose their sense of balance, which makes walking extremely difficult.

For further (enjoyable) reading see Oliver Sacks' book: "The Man Who Mistook His Wife for a Hat".

Six? Seven? There are ten senses: sight, hearing, smell, taste, touch, pressure, hot/cold, pain, kinethesis, and proprioception. The tactile sense is usually just shrugged off by attributing "nerve endings". They aren't just nerves ending, there are complex small organs, which are no less "sense organs" as the photoreceptors in the eye, the cilium cells in the ear, the nerves in the nose etc.

The warmth-coldness sense is actually made up of smaller temperature ranges. A nerve ending functions most actively at its specific temperature. There's the same kind of "spectrum" with taste and smell - there are different cells for salty, sweet, burnt, etc. Pain and heat sensors are both active at blistering temperatures. The pressure and temperature sensor are, btw, big. There are a few of them on the skin, so you can spot where they are. And still people think this diverse senses are just one sense?

All these senses are used to perceive the external reality by sensing their effect to the body. Logically, things that don't have any effect on the body, like neutrinos, cannot be sensed. Just try putting your hand into a drawer:

Are proprioception and pain senses? According to Webster_1913, a sense is a faculty to perceive properties of external objects. Proprioception is about knowing where your bodyparts are, and those do not qualify as external. The same reasoning goes for pain. Indeed you can only feel the temperature of your own skin, so even the cold/hot feeling is not that clearly a sense ; but I might be stretching the subject too much.

What I am trying to point out is that senses are not about conscious perception, but about the rest of the world : they are the only link between the outside and the mind. And with this meaning we only have five senses. Considering proprioception as a sense means you consider that your hands or your legs are not part of You, of your Self, but rather alien objects that are to be commanded. I believe that all your body is part of Yourself ; would you consider Self-Consciousness as a sense?

The five senses (touch, taste, smell, hearing, sight) refer to general, external senses. The other senses mentioned on this node are considered non-general senses, such as proprioception.

Temperature, pressure, and pain, are all aspects of touch. Treating these as separate senses is unecessarily complicated and would be like treating different colors as different senses when they are all interpreted by sight, or different tastes as different senses. Physiologists classify the five general senses based on how they relate to the nervous system, not by any subjective system developed by psychologists or Asian philosophers:

  • Taste is sensed by taste buds, and is enhanced by olfactory sensation.
  • Smell is purely olfactory, and travels to the brain through the olfactory nerve.
  • Sight is perceived from the eyes through the optic nerve to the occipital lobe.
  • Touch is perceived through general heat, pain, or pressure receptors, usually in the skin. These are all classified as touch receptors, just as the different color cones in our retinas are all classified as sight receptors.
  • Hearing is perceived by our ear drum and conducted to our inner ear (cochlea).

Interestingly, no one has mentioned any of the unconscious senses our bodies have. There are not part of the big five, but are senses nonetheless:

  • Insulin is released into our bloodstream when our body senses that our blood sugar has risen; glucagon is released when our body senses that it has fallen.
  • Our body initiates repair to internal damage that it has sensed, even though we may never consciously feel it.
  • If we use cocaine habitually, our body senses the elevated presence of dopamine and reduced the number of dopamine receptors on certain neurons in the brain, even if we are never physically aware of this dopamine consciously.
  • Some would say that some aspects of our nervous system or consciousness sense memories or information from other parts, and this influences our actions. Maybe this one is a stretch . . .

Although most people seem to be on the right track, there still appears to be a bit of confusion. There are not six senses, or ten as someone suggested, but, in fact, there remains only five. The five are as follows: vision, gustation (taste), olfaction (smell), auditory (hearing) and somatosensation. It is the last one, somatosensation, which is causing the confusion. All the extra senses that people are adding are somatosensory in origin. Somatosensation literally means "body-sense"; it is the set of senses which originates from the entire body, including skin, bone, muscle and tendon, not limited to the specialised sensory organs of the head.

Somatosensation can be broken down into proprioception, kinethesis and the cutaneous senses, which include temperature, tactile(touch) and pain. The reason why all these seemingly different senses are collectively known as somatosensation isn't just because they are all body senses, but has more to do with the structure of the brain. Different areas of the brain are associated with different functions. The area related to vision is separate in structure and function to that of hearing, and they are both separate from somatosensation. However, the area responsible for somatosensation, the somatosensory cortex, receives input from structures responsible for pain, touch, proprioception, etc. Consequently, these senses may appear to be separate entities at first glance but it is their common destination, and subsequent similarity in processing, that has combined them into a whole.

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