Most of us grew up thinking we have 5 senses. How wrong was that!
- Seeing - eyes
- Hearing - ears
- Touch - skin
- Taste - tongue
- Smell - nose
The number of senses we have is MUCH more than 5.
|Human senses are dedicated pathways that send important information to the brain|
Common knowledge makes a lot of sense. Pardon the many nonSense puns.
I am going to walk you through how many human senses there are and what they sense.
The answer that we have 5 senses is wrong. It's not 6, it's not 7. And the common mystical '6th sense' doesn't exist. Great movie though.
Before we get started on the technical aspects, I want to rule out things like the '6th sense' or 'Extrasensory perception
', etc. Under the scientific lens, they are not senses. Those things are more of processes that occur in the brain which we wrongly conceptualize as 'senses'.
- The process of information being communicated via neurons from the environment and from within the body (but outside of the brain) which has dedicated biological processes (sensory system, receptors) and dedicated mental aspects (sharpness of sound, rough texture). Let's use this definition to put things in perspective.
But is that it? Let me ask some questions that will prime you with these extra senses that we have.
- You touch something hot or cold, based on that, you feel a certain amount of pain
- You know where your legs are right now. You know where your back is.
- You know when you are moving, when you are stationary, and sometimes, when falling.
- You know if you are sitting or sleeping in a pitch black room
You know those things because you have information being collected by some sense. There are dedicated receptors that pick this information up. Then, it sends it to the spinal chord and/or the brain.
Behold, the 10 common senses that are in the human body!
What type of information is communicated by each of these senses?
(As you'll see each sense contributes a majority of the following information, not ALL of it.)
- Vision: The location of objects, colour, size, depth, shapes, visual texture, etc.
- Hearing: Volume, pitch (high or low sounds), prosody (ups & downs), sound texture (coarse, soft, deep), location of sound
- Somatoception: Texture (rough, smooth), softness, hardness, size, pressure
- Gustation: The Salty, Sweet, Sour, Umami, and Bitter tastes
- Olfaction: Smelling is quite complex. We can differentiate the intensity and type of smells. It is suspected that quantum tunnelling takes places in the olfactory receptors in the nose.
- Vestibular sense: We have a unit inside the ear that has these millions of these tiny crystals that bend tiny hair which gives information about gravity, motion, and balance. These vestibular sacs are located beyond the semi-circular ear canals.
- Proprioception: Imagine your eyes are closed and you are in a pitch black room. If I ask you to touch your left thumb to your right elbow, will you be able to do that? .... We are aware of where our body parts are even when we can't see them. The location of each part is ingrained in our brains and there is a mapping between that brain area and the body part.
- Kinesthesia: Suppose you are are falling. Spindles inside your muscles communicate information regarding the muscle tension. This mechanism communicates information about body movement.
- Nociception: There are specialized receptors called TRPV1 on the skin that communicates pain and it's intensity. This is key to survival. People who do not perceive pain (congenital analgesia) end up injuring themselves without realizing it. We don't want that to happen, do we?
- Thermoception: The same receptors that communicate pain also aid sensing temperature. Thus, hotness is perceived as painful, even if it comes from hot chili, wasabi, fire, etc.
Each of these senses has a unique pathway. From receptor cells in the body at specific places, a signal travels all the way to some part of the nervous system that interprets this information and then it helps direct behaviour.
Is that it?
There are many more pseudo-senses in the body.
- Time- the body learns to understand time-based on recurring patterns, the many circadian rhythms like sleep, hormone regulation, etc.
- Hunger - the body knows when it is hungry. It even knows when it is thirsty
- Itch - there are distinct receptors on the skin that trigger an itch response. The TRPV1 receptors on the skin that communicate Pain and Temperature information also communicate itchiness.
Depending on how we conceptualize the senses, there are at least 10 senses!
Now is that it?
Nope, still nope!
These senses don't act as single units. We do not form a perception of reality based on one sense at a time. We form a holistic perception of everything based on the deep integration of these senses in the brain. They work together and abundantly influence each other.
There are hubs across the brain where sensory information from each pathway meet and greet. These meetings send sophisticated combination signals
for the brain to interpret and then we perceive.
I'll write an article on how these senses integrate and influence each other in the future. Until then, you can check out my paper
which discusses the influence of one sense on the other. If you aren't interested in reading the whole paper, here is a short article I wrote based on that paper
You might also enjoy this article on how our senses influence each other and modify the taste of food and drinks
P.S. Fun Fact
! When you look in a particular direction to see something, your ear-drums turn in that very direction up to 10 milliseconds before the eyes! Your ears move in sync with your eyes! Isn't that cool?