How Common is Synesthesia?

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Synesthesia is a neurological process that elicits a blending of the senses and affects around 2% of the population.

What is synesthesia?

Synesthesia is not an illness. Synesthesia is a neurological trait that causes an atypical and automatic merging of the five senses in an unforeseeable but consistent way. If you remember your first days at primary school, you certainly learnt there are five senses (touch, sight, hearing, smell and taste), and each one is connected to a different sensing organ that helps to perceive what is happening around us. However, that is not the way synesthetes -that is how people with synesthesia are known- perceive the world. They feel natural senses intermingle, a sensorial perception happening simultaneously on two senses that gives a new and perplexing dimension of reality.

This means that synesthesia is, for example, smelling a colour, seeing a sound, tasting a word, seeing some characters and numbers in a specific colour (despite their original printed colour) or feeling a geometric shape when eating something. Imagine seeing number 6 and feeling a sweet strawberry taste inside your mouth. Now imagine yourself listening to your favourite song and perceiving it like seeing colours. Isn’t it amazing? Some people might think so, but for a synesthetic person, it is exhausting because of overstimulation and sensory overload. Furthermore, they usually feel social rejection, which ends in hiding their trait.

Image by Solstice Hannan, Unsplash

What are the different types of synesthesia?

There is a panoply of synesthesia types, but it often occurs with two of the five senses. Sometimes three of them might be involved, but it is less common though. Scientists have described more than 80 types of synesthesia, but what are the most common synesthesia types?

Chromesthesia is one of the most popular, and 30% of synesthetic people are believed to feel it. It is the association of sounds with colours, and just listening to a sound or a musical note can trigger the sight of colours.

Something similar used to happen to the very well-known writer Vladimir Nabokov, who was able to see colours when hearing the alphabet.

That is another type of synesthesia and is called grapheme-colour synesthesia. In some individuals, it may appear when seeing either characters or numbers, and when they are evident, they evoke the colour blue.

And finally, the spatial sequence is another of the most frequent types of synesthesia. This one makes synesthetic perceiving cardinal sequences as points in space. Sometimes, the smaller numbers are placed nearby, and the bigger ones are physically placed far away. On other occasions, people with this synesthesia type place months in a circle or see months and dates literally located in space around themselves or just in their mental space. As you can see, it appears in many forms.

You can take a look through What is the relationship between synesthesia and visual-spatial number forms? (2005) to know more detailed information.

What causes synesthesia?

Researchers and scientists do not agree about what triggers synesthesia, and as it happens in many other neurodiverse conditions, the causes of synesthesia remain unknown. What is known is that people are born with it or develop it in their early childhood, yet it can appear later.

Some researchers point out that the different cores that process our senses could be connected when we are babies, and we divided and specialise our senses on specific stimuli as we grow up. That is what researcher Daphne Maurer believes and reveals in her paper Synesthesia: a new approach to understanding the development of perception. Maurer says all babies mistake sight with hearing or touch and taste until they are three or four months.

Other different research indicates one cause of synesthesia could be that some brain areas focused on perceiving colours are physically located very close to the ones that process speech, language and music.

Scientists also believe structural and functional brain differences might be a cause of synesthesia. They say brain connections that drive sensory stimuli are much more interconnected than they usually are in a no-synesthetic.

What they know for sure is that synesthesia runs in families. So, genetics, once again, plays a role and despite the fact that it is not clear which genes are related to the trait, 40% of people with this quality have a direct relative who also has it, even if it is not the same type.

How is synesthesia diagnosed?

There is not a clinical diagnosis kit to diagnose synesthesia, but there is a five points checklist that can shed light:

• It stays the same over time: people with synesthesia tend to have the same sensations despite the passage of time.
• It is usually detected in the early years.
• It is unexpected and involuntary. It just happens.
• Individuals are able to describe and express what happens.
• It has a repetitive pattern, so it is predictable. For instance, if someone sees blue when listening to a musical note, they will always see that colour every time that note sounds.

What is known is that synesthetic usually are not aware that the way they experience reality is not the same way other people do, and most of them discover it when other people get perplexed as they share their experiences.

How common is synesthesia?

Synesthesia affects between 1% and 4% of the population, yet it is believed there are pretty much more synesthetic people than official averages show. So far, we know women are between 3 and 8 times more likely to have synesthesia than men, and it is more frequent in artists and people with a great creative sense, such as musicians or painters. Kandinsky was one of them. In fact, it seems that synesthesia provides a predisposition to poetry, music or literature skills development. In this paper Four Cases of Pitch-Specific Chromesthesia in Trained Musicians with Absolute Pitch you can find out some information about synesthesia and musicians.

In addition, you can do our online synesthesia test but remember this is not a formal synesthesia diagnosis.

 Is synesthesia considered a mental disorder?

Synesthesia is not considered a mental disorder but rather a neurological phenomenon that affects one’s sensory perception. It is a condition in which the stimulation of one’s sensory pathway leads to involuntary experiences in another sensory or cognitive pathway. 

While synesthesia was historically misunderstood and misclassified as a mental disorder, it is now recognised as an entirely natural variation in sensory perception, likely to be influenced by genetic and developmental factors. 

It is not associated with any negative impact on mental health or cognitive functioning. In fact, some individuals with synesthesia find it enhances their creativity or aids in memory recall.

Overall, synesthesia is perceived as a fascinating aspect of human perception rather than a mental disorder.

Webinar: Am I Synaesthesic?

Nat Hawley, our Head of Community, has hosted a webinar about synaesthesia. Like online synaesthesia tests, this webinar is not intended to diagnose synaesthesia. Only a qualified medical professional can make a diagnosis.

WARNING: This webinar contains flashing images. If you are photosensitive, you can skip the chapters at 13:07 and 37:57.