Synaesthesia – when the senses are working overtime

If you can hear what others are seeing or even taste what shapes look like, fear not, you are not alone

Celine Halpin, at her home near Kinnegad, Co Westmeath: like thousands of other people, Halpin has a condition where the senses have become joined and intertwined. Photograph: Brenda Fitzsimons

Celine Halpin, at her home near Kinnegad, Co Westmeath: like thousands of other people, Halpin has a condition where the senses have become joined and intertwined. Photograph: Brenda Fitzsimons


When Kate Leckie from Wicklow was six or seven, she ran into a problem. As she was colouring in her name, the “K” in Kate was, persistently and frustratingly, pink, a colour which was far from being her favourite. To make matters worse, the “e” at the end was red.

“I was conflicted as to whether I should have the letters in their own colours and risk having them clash with each other, or else just ignore it and do whatever colours I wanted,” she explains. “That feels so inherently wrong though and I guess that conflict has continued through my life.”

For Celine Halpin from Meath, as she was beginning to learn mathematics in primary school, a 3D map of the numbers was created in her mind.

“I see numbers, especially from one to 20, and I see them in a very particular way. I have heard of people who experience them as a projection in front of their eyes but it’s very much an internal thing for me,” she explains.

Leckie and Halpin like thousands of other people have synaesthesia, a condition where the senses have become joined and intertwined. Synaesthetes can be born, as the condition can be hereditary, or they can develop it. The sensations they experience are involuntary, stable and precise.

For Leckie this means she sees letters, words and numbers in colour, the colour grapheme form of synaesthesia. Halpin has four forms of synaesthesia, with the spatial sequence form being the most prominent. People with this form can experience the months and days of the week appearing in the space around them.

“The map of the months that I have in mind is very much co-ordinated with the layout of the outside of my parents’ house,” she says. “When I imagine the summer months I can see where the sun is in the sky, outside the house and I can see it shining on those months. December, for instance, is situated at the back of the house facing north and so gets less sun.

“It’s very present in my everyday cognition and in the way I remember events in time. I would find it hard to be without it,” she adds. “It’s my anchor.”

Smelling letters
But for other people, synaesthesia can mean that they taste shapes, smell letters, or that particular words or numbers take on a personality.

While there are dozens of forms of synaesthesia, the causes of the condition remain relatively unknown.

“If I see a printed word in black, I do not externally see it in colour, but it’s like I inherently and internally know the colour of the word, letter or number,” Leckie says.

For her, many of these colours are bright, which Leckie prefers – “a” is green, “b” is a deep blue, while “c”, “k” and “z” are all varying shades of pink. Unfortunately, “d”, “g” and “r” are all uninterestingly brown.

“Sometimes colours have sort of textures and patterns, ‘s’ is yellow, with tinges of green on the edges and flashes of orange throughout, the blue of ‘b’ is very deep and shiny, and ‘x’ is a very metallic, shiny silver/grey.”

It is estimated that 1-4 per cent of the population experience synaesthesia, and due to the personal nature of the condition, some people never realise that they are synaesthetes.

“I only really realised I had synaesthesia when I was an adult, and when I actually told people about what it was and what I had, everyone was pretty cool about it,” says Leckie. “I’d say as a child if I had been pretty demanding about the particular shade of orange ‘h’ was, then maybe I would’ve had a more negative experience, but it never really occurred to me to mention it.”

Halpin had a similar experience. She didn’t speak about her synaesthesia as “I just assumed that that was the way everyone else experienced things.” But as she grew older she started to question it and talk about it with her peers.

This is a very common experience, says Dr Kevin Mitchell, associate professor in genetics at Trinity College Dublin’s Institute of Neuroscience, who is exploring the causes and nature of the condition.

“Many are not aware their experiences are different from other people, or are not aware there is a name for it,” he explains.

Intriguing mystery
For scientists, synaesthesia remains an intriguing mystery, not least because of the recent research which suggests that it is nearly three times as common in adults with autism spectrum disorder.

“Synaesthesia is an interesting entry point to find out how different parts of the brain get connected to each other, especially different parts of the cerebral cortex,” Mitchell says.

The cerebral cortex has different areas devoted to different functions, such as memory, language and the senses, and it is not fully understood how cells in those areas are arranged and organised, or how the ways they are connected with each other are established. However, the assumption is that this connectivity is changed somehow in synaesthesia.

“The cortex is the one area that we really know the least about. It’s the big mystery remaining in the study of neural pathology. We know a lot about many of the other areas of the brain, we know a tonne about the spinal cord, and the cerebellum and the hippocampus but the cortex remains mysterious.”

By discovering more about the causes of synaesthesia, this may help understand other conditions such as autism.

But for Leckie and Halpin, synaesthesia is an overwhelmingly positive experience.

“I absolutely think synaesthesia has made me more creative, I am definitely into colours and colour combinations, and colours seem to have more meaning for me then perhaps other people,” says Leckie.

It has also helped her at exam time. Remembering study notes is easier “because I colour-coded them to the subject and subject headings. “When jogging or doing exercise, I can distract myself by counting down the time and focus on the colour of the numbers, which is great,” she adds. However, it can also be frustrating too. “I can get angry because I can’t colour-code everything, I just don’t have the time.”

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