In the morning, we can feel the tingle of toothpaste, hear and feel the sound of running water in the shower, smell the shampoo, and later smell the aroma of freshly brewed coffee.
Aristotle told us that there are five senses. But he also told us that the world is made of five elements, and we don’t believe that anymore. And modern research is showing that we may actually have dozens of senses.
Almost all of our experience is multisensory. We do not see, hear, smell and touch in different parts. They occur together in a unified experience of us and the world around us. What we feel affects what we see and what we see affects what we hear. Different scents in shampoo can affect the way you perceive the texture of your hair. For example, the scent of rose makes hair silky.
The flavor of low-fat yogurt can make them feel richer and thicker on the palate without adding more emulsifiers. The sense of smell in the mouth, which extends to the nasal passages, is modified by the viscosity of the liquids we consume.
My long-term colleague, Professor Charles Spence of the Crossmodal Laboratory at Oxford, told me that his neuroscience colleagues believe there are anywhere between 22 and 33 senses. These include proprioception, which enables us to know where our limbs are without seeing them. Our sense of balance depends on the vestibular system of the ear canals as well as vision and proprioception.
Another example is interoception, by which we sense changes in our body, such as slight increases in our heart rate and appetite. We also have a sense of agency when moving our limbs: a feeling that may be missing in stroke patients, who sometimes even believe that someone else is moving their arm.
There is a sense of ownership. Stroke patients sometimes feel as if their arm, for example, is not theirs, even though they can still feel sensations in it.
Some traditional senses are a combination of several senses. For example, touch includes pain, temperature, itch, and tactile sensations. When we taste something, we are actually experiencing a combination of three senses: touch, smell, and taste – or taste – which together produce the flavors we perceive in food and drink.
Gustitation covers the sensations generated by receptors on the tongue that enable us to detect salt, sweet, sour, bitter and umami (savory). What about mint, mango, cantaloupe, strawberry and raspberry? There are no raspberry receptors on our tongue, nor is there any combination of sweet, sour and bitter in the raspberry flavor. There is no flavor arithmetic for fruit flavors. We sense them through the combined functioning of the tongue and nose. It is smell that makes the greatest contribution to what we call tasting.
However, it is not absorbing odors from the environment. When we chew or sip, odor compounds are released, which travel from the mouth to the nose through the nasal pharynx at the back of the throat. Touch also plays its part, linking taste and smell together and dictating our preferences for liquid or solid eggs and the velvety, luxurious stickiness of chocolate.
Vision is influenced by our vestibular system. When you are boarding a plane on the ground, look under the cabin. Look again when you’re on a climb. This will “look” to you as if the front of the cabin is higher than you, although alternatively, everything is the same with respect to you as it was on the ground. What you “see” is the combined effect of vision and your ear canals telling you that you are leaning back.
The senses provide a rich source of research, and philosophers, neuroscientists and psychologists work together in the Center for the Study of the Senses at the School of Advanced Study, University of London.
In 2013, the Center launched its Rethinking the Senses project, directed by my colleague, the late Professor Sir Colin Blakemore. We discovered how modulating the sound of your footsteps can make your body feel lighter or heavier.
We learned how audio guides at the Tate Britain art museum address the listener as if the model in a painting is speaking, helping visitors remember the more visual details of a painting. We found out how plane noise interferes with our perception of taste and why you should always drink tomato juice on the plane.
While our perception of salt, sweet and sour is diminished in the presence of white noise, umami is not, and tomatoes and tomato juice are rich in umami. This means that the noise of the plane will enhance the delicious taste.
In our latest interactive exhibition, Senses Unwrapped, at Coal Drops Yard in King’s Cross, London, people can discover for themselves how their senses work and why they don’t work the way we think they do.
For example, the size–weight illusion is illustrated by a set of small, medium, and large curling stones. People can pick up each one and decide which one is heaviest. The smallest one seems to be the heaviest, but then people can put them on a balance scale and find out that they weigh the same.
But there are always so many things around you that show how complex your senses are, if you just stop for a moment and take it all in. So the next time you’re out walking or tasting food, take a moment to appreciate how your senses are working together to help you feel all the sensations. 
Barry Smith, Director of the Institute of Philosophy, School of Advanced Study, University of London. This article is republished from The Conversation under a Creative Commons license. Read the original article.
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