Coming to Our Senses

People are more likely than not to think they have just five senses. But why five? Although you naturally think of sight, sound, touch, taste and smell, you also have a sense of balance due to your vestibular system; the fluids in your ear canals that tell you whether you are going up or down in an elevator, and whether you are tilting forwards or backwards.

Along with this sense, you have proprioception, that tells you where your limbs are without having to look at them or feel them. In fact, we may have as many as thirty-three senses, according to cognitive neuroscientists. This is due to systems of sensors that allow us to detect movement, pain, pressure, light, heat, stinging or cooling. We have senses you may never have heard of, like interoception: a sense for detecting subtle changes in our internal state, like fluctuations of our heart rate, or butterflies in the stomach.

And it’s not just that we have many more senses than the five Aristotle made us think about, the senses also work together, influencing each other’s outputs. Take vision and balance. When you stand on one leg you wobble a little but you're probably pretty stable. But now try standing on one leg when your eyes are closed. You will be much less stable and that’s because your visual system works in tandem with your vestibular system to provide correcting signals and anchoring. And it’s not just one-way traffic. The vestibular system influences what you see, providing one of the clearest examples of the fact that the senses don't work in isolation.

The next time you are on an aircraft strapped into your seat and listening to the safety announcement, look along the cabin and see where everything is. Then look along the cabin again when you are in the climb. Now it looks as if the front of the cabin is higher than you are. Of course it is, but it’s not your eyes that are telling you this. How could they? You are in exactly the same optical relation to everything in the cabin as you were when the plane was on the ground. What’s happening is that because your ear canals are telling your brain that you are tipping backwards, the brain changes what you see to reflect what’s going on around you. If we could manipulate the fluid in your ears to give you the impression to tilting backwards while you sit upright in a chair, the room in front of you would appear to be sloping up.

Professor Barry Smith

Professor Barry Smith is the AHRC Leadership Fellow for the Science in Culture Theme.

His new 10-part series, The Uncommon Senses, starts on Monday 20 March at 1.45pm on BBC Radio 4 and also available via iPlayer.

This cross-talk between the senses — how they influence one another’s workings — is a major research topic for philosophy, psychology and neuroscience. The multisensory integration of the inputs that shape our experience of the world around us and ourselves was the theme of an Arts and Humanities Research Council Large Grant under the Science in Culture theme led Professor Sir Colin Blakemore. The research of this cross-disciplinary team is drawing the attention of artists, designers, filmmakers, all keen to learn more about the way our multisensory experience is shaped by the interaction of so many different sensory systems. My own research on flavour perception provides one of the richest fields in which to explore sensory interactions since eating and drinking are among the most multisensory parts of everyday experience. What we call tasting is always an amalgam of touch, taste and smell. If you eat a menthol lozenge, the flavour is always three things: a minty aroma, a slightly bitter taste and a cool senseation in the mouth. Take one of these away and it is not the ‘taste’ of menthol.

In the course of eating the brain is constantly working to integrate the different sensory inputs to provide us with a unified experience of flavours. How it is does this is subtle and complex. How things feel can affect how they smell, and vice versa. Certain odours in yogurts that make them taste creamier. And most of what you think you are tasting with the tongue is actually due to the nose. Pinch your nose tightly closed and you won’t be able to tell the flavour of the jelly-bean you are chewing. It’s only when the nose is brought back into play that you taste the raspberry, cherry, peach or melon flavours. You don't have melon receptors on the tongue: all these fruit flavours are due to smell, and its is the combined input of smell and taste, along with the creamy, sticky, chewing, or crunchy feel of our foods that creates the single unified experience of a food’s flavour. This complex, multisensory experience of eating inspires chefs like Heston Blumenthal, with whom I collaborate, to play creatively with the senses of his diners to give them surprises and delights that amaze and intrigue, enhancing their perception and appreciation of flavour.

It is a great time to put the creative and culinary arts together with the sciences and the humanities to explore a fundamental but everyday part of what it is to be human, and it all starts, close to home, in the intimate world of our senses.

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