Colours, Letters, Numbers and Sounds in The Fascinating World of Synesthesia
Aug 15, 2025
It began with what I thought would be a simple, straightforward exercise.
I handed my young patient a chart filled with numbers in a rainbow of colours, expecting him to read them aloud with ease as I knew he was confident with colours and numvers.
Instead, he paused, brow furrowed. His eyes flicked across the chart, as he sanned the numbers and letters before he he looked up and said something that almost stopped me in my trcks, “these colours are wrong.”
At first, I thought he meant that I had accidentally printed the wrong version of the chart. But as he began to explain, I realised something far more fascinating was happening.
To him, numbers and colours were not separate things—they were inseparably linked in his mind, but not in the way I had displayed them. What looked perfectly fine to me, felt as though the world had been turned upside down.
This primary school boy is part of a select few with colour-grapheme synesthesia, experiences numbers, letters, musical notes and even certain songs as inherently tied to specific colours. What I saw as numbers with different colours on a chart, he saw as the world being flipped upside down.
That moment became a beautiful teaching, showing me that no two people perceive the world in exactly the same way.
For him, these colour associations are lifelong, automatic, and unchangeable. They’re not imagined colours—they are experienced as vividly as you and I see the sky as blue or the grass as green.
He shared that purple is painful for him — not just unpleasant to look at, but also something he can feel.
Fluro yellow and fluro pink have a similar effect, not only are they super bright but they are almost physically irritating.
In contrast, forest green feels neutral — neither comforting nor uncomfortable.
For this child numbers also have fixed colours in his mind, which is why using a coloured number chart initially caused confusion. The colours didn’t match the ones his brain had always associated with each number.
Here are a few examples of his synesthetic colour associations;
A = Red
B = Orange
C = Yellow
J = Purple
W = Blue
When he said the letter J, the discomfort that purple brings was something he could feel and see, and those of us in the room could feel and hear.
Synesthesia, from the Greek roots meaning “joined perception,” is a neurological phenomenon where the stimulation of one sensory or cognitive pathway automatically triggers another.
For example, a person with synesthesia might:
See colours when hearing music (chromesthesia).
Taste flavours when reading words or hearing sounds (lexical-gustatory synesthesia).
Feel physical sensations in response to colours or sounds (mirror-touch synesthesia).
One of the most common forms is colour-grapheme synesthesia, where letters, numbers or even days of the week are perceived as having specific, consistent colours.
While synesthesia involves an automatic sensory link—such as seeing a colour when reading a number—ideasthesia focuses on the brain’s association of meaning with sensory experiences. Synesthesia is often described in terms of direct sensory connections (for example, seeing a colour when hearing a sound). In contrast, ideasthesia is triggered not purely by the sensory input itself, but by the underlying concept, meaning sparks the sensory experience such as associating a particular personality with a specific shape or symbol.
Both phenomena offer fascinating insights into how the brain integrates and processes information, highlighting its remarkable ability to blend and crosswire experiences—and revealing just how fluid perception can be.
For many, synesthesia is not a diagnosis or disorder to be “treated,” but a lifelong gift—one that blends senses to create a uniquely vivid tapestry of perception. It can shape creativity, enrich identity, and inspire fresh ways of experiencing the world. Artists, musicians, and writers often credit synesthesia with providing a wellspring of unique ideas and sensory inspiration.
Once considered rare, recent studies suggest that up to 4% of the population may experience some form of synesthesia, though many remain unaware that their way of perceiving is uncommon. For those who live and work with it, embracing synesthesia as a gift can deepen self-understanding and expand creative expression.
For those living and working with synesthesia, choosing to embrace it as a gift can enhance creativity and self-understanding.
Here are a few strategies to thrive with synesthesia:
Celebrate the Difference: Recognise synesthesia as a point of difference that provides a unique lens on the world. Many artists, musicians and writers credit synesthesia for their creativity.
Find Support: Connecting with others who share this experience can foster community and validation.
Adapt Environments: As a vision therapist, I adapt my tools and methods to align with how each synesthetic patient perceives their world. For educators, caregivers, and employers, understanding these differences can have a profound impact. Whether in education, therapy, or the workplace, adjusting approaches and environments to match an individual’s sensory reality can make a meaningful difference.
The scientific exploration of synesthesia began in the 19th century with pioneers like Francis Galton, but meaningful research only gained momentum in the late 20th century with advances in neuroimaging.
Findings so far reveal that:
Synesthesia is linked to enhanced connectivity between sensory brain regions.
It provides insight into how the brain integrates senses and forms perception.
Synesthetes often excel in creative and memory-based tasks, possibly because their sensory crossovers create additional “hooks” for recall.
Today, studies offer valuable insights into:
Brain Development: Synesthesia likely stems from increased cross-talk or cross-wiring between sensory regions in the brain.
Integration of Perception: Studying synesthesia deepens our understanding of how sensory systems can overlap, blend, and enhance each other.
Creativity and Cognition: Many synesthetes show heightened neural connectivity, which may contribute to their often exceptional creative abilities..
Researchers tend to distinguish between two types of synesthetes:
Associators perceive colours or sensations in their “minds eye,” more like a mental association.
Projectors physically see the colours or sensations imposed on the object itself, reflecting stronger cross-wiring in the brain.
As I work with patients who experience the world in unique ways, I am continually reminded of the power of perception and the importance of adapting to each individual’s needs. Every session becomes a window into a different kind of reality—one where senses weave together in unexpected and beautiful ways. Whether it’s seeing numbers in colours, hearing sounds in shapes, or perceiving life through an entirely different lens, each perspective holds its own beauty and truth.
Working with synesthetic patients, like this child, is always exciting because it challenges me to pivot and adapt my methods to their unique cognitive and sensory experiences. Each session becomes both a discovery and a lesson, offering new insights into how the brain perceives, integrates, and makes meaning of the world. I hope it serves as a gentle reminder that our own way of seeing is not the only reality.
By shifting the way I approach therapy, I am not just helping them navigate their world—I am also learning to see the world differently myself. Never will we truly see through the eyes of another person, but moments like this remind me that we can always try to understand and celebrate their perspective.
Synesthesia reminds us of the vast, untapped potential of human perception. It challenges us to see the world through a lens of curiosity, creativity and adaptability. For those with synesthesia, it is a beautiful gift that reveals the boundless connections within the human brain, rather than a quirk or anomaly.
People with synesthesia often describe their experiences in vivid, uniquely personal ways—sometimes using poetic, almost otherworldly language to capture the beauty and depth of their sensory overlap.
Here are some examples of what they might say to describe their world:
Color-Grapheme Synesthesia (Seeing Numbers/Letters in Color)
“The number 7 is always bright yellow, like the sun on a summer day.”
“When I see the word ‘Monday,’ it’s deep purple with a hint of green.”
“Letters feel alive with their colors; ‘A’ is always red, and ‘Z’ is calming blue.”
Chromesthesia (Hearing Sounds as Colours)
“Every time I hear a violin, I see golden ribbons flowing in the air.”
“The sound of thunder flashes a jagged streak of silver across my mind.”
“A jazz saxophone is like seeing swirling orange and purple smoke.”
Lexical-Gustatory Synesthesia (Tasting Words)
“When someone says the word ‘blue,’ it tastes like blueberries on my tongue.”
“The name ‘Emily’ tastes like honey mixed with cinnamon.”
“Hearing ‘holiday’ feels like biting into a juicy watermelon.”
Mirror-Touch Synesthesia (Feeling Sensations of Others)
“When I see someone touch their face, I can feel it on my own cheek.”
“Watching someone get a paper cut makes my ears ring.”
“When my friend hugged someone, I felt the warmth on my arms too.”
“If you scratch your arm, my arm tingles too.”
Spatial Sequence Synesthesia (Visualising Time or Numbers in Space)
“The days of the week are arranged in a circle, and Wednesday is always at the top.”
“When I think about the year, I see it as a long ribbon stretching into the distance.”
“Numbers float in a staircase pattern, with 10 always higher than 9.”
Auditory-Tactile Synesthesia (Feeling Sounds)
“The sound of a piano feels like raindrops landing softly on my skin.”
“Bass-heavy music makes my chest vibrate with a warm pulse.”
“Birdsong feels like tiny tickles along my arms.”
Olfactory-Visual Synesthesia (Seeing Smells)
“The smell of coffee is a rich, warm brown that swirls around my head.”
“Roses smell pink to me, like a soft pastel cloud.”
“The scent of fresh-cut grass sparkles with bright green light.”
Below are general descriptions of the experiences reported by people with various types of synesthesia.
“It’s like my senses are always holding hands and everything feels connected.”
“Music is never just sound; it’s like watching a movie of colours and shapes.”
“The world feels even more alive because numbers, letters and sounds all have personalities.”
“Every sensation is a mix; it’s like living in a constant kaleidoscope.”
These descriptions highlight how synesthetes experience the world in multidimensional, often poetic ways that enhance their perception and interaction with their surroundings.
Working with synesthetic patients has profoundly reshaped the way I approach my profession—changing me as much as it helps them. Every session becomes a window into a reality where senses are woven together in unexpected and beautiful ways, reminding me that perception is personal, never universal. By listening, adapting, and celebrating these sensory connections, I not only help patients engage more fully but also learn new ways of seeing the world. There’s a deep humility in recognising that my own perception is not the default or the gold standard. We may never truly see through another’s eyes, but we can honour their way of seeing—and in doing so, expand our own.
Synesthesia isn’t just a neurological curiosity. It’s a mirror for empathy. It reminds us that:
What is obvious to one person may be invisible to another.
The same reality can be experienced in wildly different ways.
Adapting to someone’s way of seeing isn’t just kindness—it’s respect.
The next time you meet someone who perceives the world differently—whether through synesthesia, cultural background, life experience, or personal perspective—remember: we may never fully see through their eyes, but we can listen, learn, and celebrate the beauty of their vision.
For synesthetes, the world is a living, breathing canvas.
For the rest of us, their experiences are an invitation—to imagine more, notice more, and embrace the full spectrum of what it means to be human.
Synesthesia invites us to ask:
What if we all looked at our differences not as barriers, but as bridges?
What if we leaned into curiosity instead of comparison?
For those with synesthesia, the world is a kaleidoscope—ever-shifting, impossibly intricate, and deeply personal. And for the rest of us, their stories offer an invitation: to notice more, to imagine more, and to remember that perception is far more than what meets the eye.
