Why Humans Could Have As Many As 33 Senses

Stuck in front of our screens all day, we often ignore our senses beyond sound and vision. And yet they are always at work. When we’re more alert we feel the rough and smooth surfaces of objects, the stiffness in our shoulders, the softness of bread.

In the morning, we may feel the tingle of toothpaste, hear and feel the running water in the shower, smell the shampoo, and later the aroma of freshly brewed coffee.

Aristotle told us there were five senses. But he also told us the world was made up of five elements and we no longer believe that. And modern research is showing we may actually have dozens of senses.

Almost all of our experience is multisensory. We don’t see, and hear, smell and touch in separate parcels. They occur simultaneously in a unified experience of the world around us and of ourselves.

What we feel affects what we see and what we see affects what we hear. Different odors in shampoo can affect how you perceive the texture of hair. The fragrance of rose makes hair seem silkier, for instance.

Odors in low-fat yogurts can make them feel richer and thicker on the palate without adding more emulsifiers. Perception of odors in the mouth, rising to the nasal passage, are modified by the viscosity of the liquids we consume.

My long-term collaborator, professor Charles Spence from the Crossmodal Laboratory in Oxford, told me 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 looking at them. Our sense of balance draws on the vestibular system of ear canals as well as sight and proprioception.

Another example is interoception, by which we sense changes in our own bodies such as a slight increase in our heart rate and hunger. We also have a sense of agency when moving our limbs: a feeling that can go missing in stroke patients who sometimes even believe someone else is moving their arm.

There is the sense of ownership. Stroke patients sometimes feel their, for instance, arm is not their own even though they may still feel sensations in it.

Some of the traditional senses are combinations of several senses. Touch, for instance involves pain, temperature, itch and tactile sensations. When we taste something we are actually experiencing a combination of three senses: touch, smell and taste – or gustation – which combine to produce the flavors we perceive in food and drinks.

Gustation, covers sensations produced by receptors on the tongue that enable us to detect salt, sweet, sour, bitter and umami (savory). What about mint, mango, melon, strawberry, raspberry?

We don’t have raspberry receptors on the tongue, nor is raspberry flavor some combination of sweet, sour and bitter. There is no taste arithmetic for fruit flavors.

We perceive them through the combined workings of the tongue and the nose. It is smell that contributes the lion’s share to what we call tasting.

This is not inhaling odors from the environment, though. Odor compounds are released as we chew or sip, traveling from the mouth to the nose though the nasal pharynx at the back of throat.

Touch plays its part too, binding tastes and smells together and fixing our preferences for runny or firm eggs, and the velvety, luxuriousness gooeyness of chocolate.

Sight is influenced by our vestibular system. When you are on board an aircraft on the ground, look down the cabin. Look again when you are in the climb.

It will “look” to you as though the front of the cabin is higher than you are, although optically, everything is in the same relation to you as it was on the ground. What you “see” is the combined effect of sight and your ear canals telling you that you are titling backwards.

The senses offer a rich seam of research and philosophers, neuroscientists and psychologists work together at the Centre for the Study of the Senses at the University of London’s School of Advanced Study.

In 2013, the centre launched its Rethinking the Senses project, directed by my colleague, the late Professor Sir Colin Blakemore. We discovered how modifying the sound of your own footsteps can make your body feel lighter or heavier.

We learned how audioguides in Tate Britain art museum that address the listener as if the model in a portrait was speaking enable visitors to remember more visual details of the painting. We discovered how aircraft noise interferes with our perception of taste and why you should always drink tomato juice on a plane.

While our perception of salt, sweet and sour is reduced in the presence of white noise, umami is not, and tomatoes, and tomato juice is rich in umami. This means the aircraft’s noise will taste enhance the savory flavor.

At our latest interactive exhibition, Senses Unwrapped at Coal Drops Yard in London’s King’s Cross, people can discover for themselves how their senses work and why they don’t work as we think they do.

For example, the size-weight illusion is illustrated by a set of small, medium and large curling stones. People can lift each one and decide which is heaviest. The smallest one feels heaviest, but people can them place them on balancing scales and discover that they are all the same weight.

But there are always plenty of things around you to show how intricate your senses are, if you only pause for a moment to take it all in. So next time you walk outside or savor a meal, take a moment to appreciate how your senses are working together to help you feel all the sensations involved.

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