When rainbows taste like chocolate and music smells like roses

Ekaterina Turlova
11 July 2017

Above: Base image © Wikimedia Commons

Have you ever wondered what colours sound like, or what words taste like? There are people out there who can tell you!

We all rely on our senses of touch, taste, smell, sight and hearing to let us know what’s going on around us. But for some people, the senses can get a little mixed up. That’s what happens in a really cool condition called synesthesia.

Synesthetes, people who have this condition, find that stimulating one sense leads to the stimulation of another. So for example, when they hear something, they might taste something at the same time, even if there’s nothing in their mouth. And this happens completely involuntarily!

Did you know? Some researchers have estimated that 1 in 23 people have some type of synesthesia.

Some researchers have estimated there are as many as 150 variations of synesthesia. Here are a few examples:

Grapheme-colour synesthesia

When a grapheme-colour synesthete sees a certain letter or number, they also see a certain colour. For example, the letter “A” may always look dark red, while “B” may always look blue. This is one of the most common types of synesthesia.

Auditory-tactile synesthesia

When an auditory-tactile synesthete hears a certain tone, word or a musical sound, they also feel a sensation somewhere on their body - a touch on the shoulder or a pat on the back, for example.

Word-taste (or lexical-gustatory) synesthesia

When a word-taste synesthete hears or sees certain words, they’ll experience a particular taste. This type of synesthesia is very rare.

One word-taste synesthete, James Wannerton, put together a London Underground taste map. In it, he replaced the names of London’s subway stations with descriptions of what he tasted when he read or heard these names. Some stations tasted pretty good, like thin crispy bacon and bubble gum. But others tasted like candle wax, putrid meat and burnt rubber!

He put together a taste map of Toronto subway system as well. Here, too, he tasted a wide range of things, from Mars bars to fried onions to hair spray!

Smell-colour, flavour-colour and even personality-colour (commonly known as seeing “auras” around people) are just a few more examples!

How much synesthesia can a person have?

Sometimes one person can have multiple types of synesthesia. Solomon Shereshevsky was famous for his incredible memory. He could remember complex mathematical formulas, poems and even lengthy speeches thanks to his many types of synesthesia: he associated words and text with temperature, weight, and colour. His memories were so strong, they could last years!

Shershevsky’s synesthesia had a downside, though. Sometimes, he’d find reading difficult because the written words produced very distracting sensations. Do you ever read while you eat? Imagine what that would have been like for Shereshevsky, especially if the “taste” of the words he was reading didn’t go with the taste of the food he was eating!

Did you know? Because synesthesia doesn’t usually interfere with a person’s daily functions, it’s not considered a neurological disorder.

The science of synesthesia

In your brain, different regions have different jobs. For example, your visual cortex processes the visual information you receive from the environment. It can recognize colour, movement and light. Your temporal lobe processes auditory information (things you hear), and your somatosensory cortex processes touch and other similar sensations.

Several theories exist about how synesthesia happens. For example, cross-activation theory suggests that as the synesthete’s brain develops, these regions become interconnected more than usual. So, when a stimulus (like a touch) activates one region in the brain, another region (like the visual cortex or temporal lobe) may be activated at the same time.

Did you know? People with certain conditions, like temporal epilepsy, can experience synesthesia even though they’re not synesthetes.

Synesthesia in technology

The concept of synesthesia has led to many cool applications. For instance, researchers are studying how artificial synesthesia can help with pain management. Through virtual reality, artificial synesthesia combines sight, sound and touch sensations to shift a patient’s attention away from their pain.

Another cool example is a device called Eyeborg. It combines auditory and visual stimulation to allow colour-blind people to hear colours. Want to know what it’s like to hear colours? Listen here.

What is it like to live with synesthesia?

While Solomon Shereshevsky’s condition caused him some trouble, most synesthetes say it’s a pleasant condition to live with. It can even be inspirational - many synesthetes are artists and composers!

Want to know if you have synesthesia? This test may be able to help you find out: http://www.synesthete.org

Learn more!

The sound of color (2012)
J. Akst, The Scientist.

Neurophysiology of synesthesia (2007)
E. Hubbard, Current Psychiatry Reports 9.

Synaesthesia: the taste of words on the tip of the tongue (2006)
J. Simner & J. Ward, Nature 444.
Link to abstract. Subscription required to access full text.

Mechanisms of synesthesia: Cognitive and physiological constraints (2001)
P.G. Grossenbacher & C.T. Lovelace, Trends in Cognitive Sciences 5.
Link to abstract. Subscription required to access full text.

Ekaterina Turlova