Synesthesia – What is it and how to diagnose it?

synesthesiaSynesthesia or Synaesthesia is a very interesting phenomenon. It is a condition of the mind resulting when the brain’s processing centers of the senses are interconnected.  People who “suffer” (or better benefit) from it, experience the world in a very different and unique way. They are called synesthetes.


So, how do these people experience their lives? They can “hear” or “taste” colors, they see colored letters, they can “see” sounds, and they perceive a sensation with more than one senses. For example, a smell can engage their vision or any other sense. They are not hallucinating they are just synesthetes.


Synesthesia is a strange mix of the senses perception that can be expressed in various forms. Some people may see the sounds while some others may listen to the smells or they can feel drawings. According to a study of Dr. Simon Baron-Cohen, professor of psychology at Cambridge University, it is estimated that one person out of 2000 is a synesthete. The scientist and synesthete Sean Day created a list of 40 different expression forms of the condition. In most of them, shapes, smells, sounds and tastes acquire colors.

The Hidden Sense: Synesthesia in Art and Science (Leonardo Book Series)
The Hidden Sense: Synesthesia in Art and Science

For understanding Synesthesia, the first step was to be defined as a real perception that is stable in time and not periodical. Initially, it was believed that it had to do with memories and experiences from the childhood. According to another interpretation, when someone is a synesthete confirms that the number 5 is red, and the number 7 is green. However, none of these theories explains why we are not all synesthetes.


Some scientists believed that this phenomenon had a biological aspect, and they decided to research the brain condition of synesthetes with the help of modern technology. Many theories trying to explain this phenomenon have been developed and are being developed as research goes on.


One interesting approach formed by the neurologist Richard E. Cytowick in the ’80s. Cytowick supported that this disturbance is due to the unusual activity of the brain area that is connected with the senses. This area is the most primitive part of the human brain. According to the neurologist, all the information from the senses is concentrated in the hippocampus of the brain where they are being evaluated.


MRI (Magnetic Resonance Imaging) research confirmed that Synesthesia, which is related to colors and numbers, is due to the parallel activation of the V4 and neighboring areas of the brain. V4 area is responsible for processing information about colors.


When we see a particular number or letter the parts of the cortex, which are connected with the representation of the forms, are engaged. But in synesthetes the area V4 is also engaged at the same time. Scientists believe that there are more connections between the different parts of the brain, resulting in the communication of neighboring areas in the brain of synesthetes.


Other theories are based on the development of similar connections between different areas of the brain that are responsible for the sensory perception. For example, the center of the auditory sense is neighboring with the part of the brain that accepts stimuli from the V4 area. As mentioned earlier, V4 is related to color perception. This adjacency may explain the connections between sound and color.


The Synesthesia expression that involves taste and touch senses may be due to connections between the area of the taste and an adjacent area that controls touch. But the question of why this phenomenon is limited only to some people is still unanswered.

Francis Galton observed that in families where there was at least one synesthete, it was possible to be other synesthetes as well. A study of some psychologists of Trinity College in Dublin was published in 2006 and showed that 42% of synesthetes have at least one first-degree relative with the same particularity. Some people believe that Synesthesia is connected with a dominant gene in the chromosome X, which is transferred from mother to children. And also this is the reason that the phenomenon is presented mostly to women.

There is no explicit connection between creativity and Synesthesia. Scientists confirm that the expression of this condition is due to more connections between different areas of the brain. Because of these connections, senses can also be triggered by ideas or thoughts and not only from external sensory stimuli, as it was believed until now. Some people do not agree with this explanation as it has not scientifically proved.


Synesthesia is a fascinating field of research that contributes to the study of perception and consciousness. Many specialists certify that further research of this phenomenon will reveal new discoveries in the field of neurological research which is related to linguistics and metaphorical meanings.


Synesthesia Test – Try Your Senses

Many synesthesia tests can show if someone is a synesthete. A simple one is showing in the following picture. An average person will not observe anything unusual.



A synesthete would likely see different letters in different colors. The next picture gives an idea of how he/she would see this drawing.



Colored Numbers?


A typical expression of synesthesia is the mix of figures and colors. The American scientists Vilayanur S. Ramachandran and Edward Hubbard created the following test to study this kind of synesthesia.



As you can see in the picture above, there are groups of the numbers 5 and 2 in gray color. A synesthete can identify immediately the number 2 because he sees it in a different color. The next picture shows what he would probably see.



If you would like to know more, also check the following books:


A Natural History of the Senses

The Man Who Tasted Shapes (Bradford Books)


Are you a synesthete? Let us know your interesting experience in the comment section.


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39 comments on “Synesthesia – What is it and how to diagnose it?

  1. I’d like to point out that synesthesia is not a “disease”. It is actually a benign condition that generally benefits those who have it. Classifying it as a “disease” is both incorrect and misleading.

  2. Hi Kate,

    As you can understand from the article, I don’t treat synesthesia as a disease but as a very interesting phenomenon. However the general conception is that synesthesia is classified as a “disease” just because it is a condition different from normal.

    This article is not to insult any synesthete but just to describe how differently, uniquely and interestingly these people perceive the world.

  3. Great write-up. One thing that I think is especially interesting about synesthesia is the amount of information that we don’t know. Over time, the neurological aspect of the condition will become more and more clear (hopefully), shedding a whole new light on what we know now.

  4. Interesting write up. I believe that my 11 year daughter is a synesthete. Would love to hear from synesthetes, Is there a club where synesthetes can share experiences,

  5. I am a grapheme-colour synesthete and I find synesthesia being called a disease insulting. I consider it a put-down to synesthetes.

    • Hi Emily,

      As I have already pointed out in reply to another comment, this article’s purpose is not to insult anybody. It just presents briefly what synesthesia is. But I believe you are right about the term “disease” as synesthesia is not a mental illness. Medical community had classified synesthesia as a disease in the past because they didn’t know much about it. This conception changed however as more and more studies analyzed this condition.

      I am sorry if you feel insulted, I removed this term from the article as I believe that you have a point and to be honest I wish I could experience synesthesia in the first hand. I believe that synesthetes are blessed people.

  6. I have something like this except all the colors I see are in my mind but I could actually draw what a song looks like and how something taste with colors cause when I listen to music a series of colors goes through my mind depending on the sound and words and songs have a color all number have a color and letters. For me everything has its own color and I have a great memory because I remember things with a color that is automatically associated with it… Wich is probably why I remembered everybodys birthday in my class. This might be what I have or something very close. This was a great article! Thanks!

  7. I found this website by typing ‘seeing numbers as colours’ into the browser.
    Pleased to find there’s a lot of us!
    Typical synsthese being left handed, I work with design and colour for a living, even playing with toys of the same colour as a living.
    Conversely – and I wonder if anyone else is the same – I have a poor sense of smell and taste, but excellent hearing and sight. Anyone else similar?
    I see letters and numbers as colours, helpful to memorise numbers!
    What is curious is that there is no consistency between people of the ‘cross-referencing’ numbers to colours.

    Here’s my list anyway:
    1 = white; 2 = pale pink; 3 = pale yellow; 4 = bright red; 5 = dark brown; 6 = black; 7 = mid green; 8 = biscuit colour; 9 = pale blue; 0 = clear (see-through).

    • Haha same. Except, my number-color combinations are completely different, except for three. 1 always = black. 2 = any shade of green, usually light though, 3 = usually any shade of yellow, can be orange, 4 = orange to a dark red 5 = red or yellow 6 = blue or (rarely) purple, 7 = fuschia to dark purple, 8 = never blue, can be dark red, purple or orange, 9 = not really sure, buts its always a dark color and is never warm. 0 = white. It depends on how colors are matchd as well. 707 is lilac white lilac. My mom hasthe number thing too, we even agree on some. Words have color associations as well, I remember hating certain words as a kid because they had strange colors.
      Another thing is that, especially with 2, if someone writes them differently, it really bothers me. I couldn’t focus once when my math teacher wrote 2 in red lol.

      • I think everyone has his or her own pairing of color and number (for me even letters). I also have the colors just inside my head, though I have noticed the 2s on the picture. 707 pink-white-pink for me. 🙂 What I have noticed is (inside my head) words and days of the week and months (and even numbers bigger than 9) have their own color, like moods and music (I think it is connected to the mood not really to the sound for me). And I think about months of the year as “wearing a skirt” if someone understands what I am talking about – June is in front of me a bit left.
        If someone wrote them differently or pointed to a different direction it would also bother me.
        My mother told me she sees the numbers colored as well. Though she is not a creative artistic type of person at all.
        Just wanted to share. It’s good to “meet” similar people. 🙂

  8. the multicolored “synesthesia” on the top of the page is not an accurate depiction of what colored letters would look like to a synesthete, because the colors for the three s’s and the two e’s are all different, when they should be the same.

    also, synesthetes can’t usually see the 2s apart from 5s like in the second colored picture, at least not immediately. The whole thing isn’t colored until you focus on it, looking for the 2s. But synesthetes can find the triangle a lot quicker than nonsynesthetes.

  9. i’m a synesthete; and i had to put my hand over the screen when it came to photo representations of synesthesia cause when the colors of letters and numbers aren’t right it give me a migrane.

  10. Some claim (though it’s not at wikipedia) that synesthesia was first mentioned in the Bible, in Exodus 19:16, where the Israelites “saw the sounds”.

  11. I recently discovered this phenomenon after watching a show on super memory i find it fascinating however i am a little confused , you see i have always associated numbers with colours but i don’t physically see them that way : in the first picture of the 5’s and 2’s it was black however i did notice the triangle of 2’s almost instantaneously.
    if someone on the other hand shouts different numbers to me i see them big and in a specific colour the same applies to letters i also experience memory and personalities with different tastes..

    so i’m just curious is this normal or potentially related to synesthesia?

  12. I am also a synesthete, and I see colors when I hear notes. I also feel emotions with the colors. Many of my students do as well…. I have found that I also have “absolute color memory” like with paint chips in Lowes or Home Depot… I can walk right up to the wall and pick up the exact chip I need from the entire wall based on a swatch of fabric I left at home or a crayon or something. I also have perfect pitch. Wierd! I just wrote a Blog about this on my Please comment! Thanks!

  13. I don’t know if what I experience qualifies as synesthesia but here is what I see:
    In my mind and on demand, a “ribbon” appears as a timeline of dates and events. I can literally see it, scroll the timeline to a needed time period, place an event or call up an event or date or name that has been placed there. Where my information is sparse the timeline ribbon is dark and only the years are visible. Where my knowledge is strong, the timeline ribbon is bright, has colors, dates, levels and in some places pictures. The ribbon has a very definite shape and twists and turns but it ALWAYS appears in the same shape. As I have grown older (in my 60’s) I am beginning to have blank spots and I believe that I am forgetting things. I never told anyone about it until very recently but people were always fascinated by my ability to pull up facts and dates, etc. in conversations saying, “you must have a photographic memory” which I don’t. So, what do you think, is this a form of synesthesia?

    • Hey, Edd!!!!

      Indeed that is a form of synesthesia!!!! It’s known as Spatial Sequence Synesthesia.



  14. I guess mines a little different than your guys’. I get these tastes in my mouth sometimes when I look at something. Everyone also has a color to me. I’m horrible with names, but I can always remember a person’s color. Music sometimes is colors too. I’ve never known there was a name for this! I’ve never seen numbers or letters as colors, or anything else like that though.

  15. I’ve read about this before and have always found it interesting.

    When I was a toddler my parents gave be a magnet board of letters. I was born half deaf so they often used it to teach me proper speech. Each of the magnets were a different color. A was red, B was orange, C was yellow, D was green, E was blue, F was purple, and then repeat.

    For many years after and well into high school I was able to decipher anything i wrote into those colors. Even today I associate P with green, W with blue, M with red, and Z with orange. However, i don’t SEE them.

    I didn’t know if perhaps associative patterns of childhood attributes to how a person with Synesthesia sense something for the rest of their life. If colors of letters on their favorite toy or smells when they first hear a song implants an association that their mind brings up easily due to the biological connections in their minds.

  16. Throughout my life I’ve always color coded everything. I always thought it was just me being really thorough with my notes but then I started realizing when I didn’t color code notes I couldn’t remember that chunk of notes. I also realized my notes had a pattern to the colors I chose. writing in purple, pink, or blue makes things easiest to remember. Red and black slip away from my memory pretty easily and then if it’s highlighted in a bright color I can remember what I wrote almost word for word. I’m 16 and have not told anyone about this. I already take antidepressants, have ADD, and suffer from migraines so I’m scared to tell people and have them think I’m just imagining it or something. I would really like some guidance. I’m not sure if I have synesthesia or not. Beyond the color memory thing I also experience other things that are making me wonder if I do have it. Please someone help. A web group or blog would be something I am interested in.

  17. I’d like to say that I have synesthesia, and I’m 100% sure that I do (and I have letter- and number- color synesthesia). I’m not a projector at all. I see the colors from my mind’s eye, so if I visualize the pictures, I can see different colors, but if I don’t visualize the pictures, I see the pictures like any ‘associater’ synesthete might.

  18. Hey guys,

    I can see sounds. I see the sound of bullets as a circle insinde another circle to the left and the sound of a generator as bubbles. Am i synesthate?

  19. This evening, I was reading a Wikipedia entry about Yevgeny Ivanovitch Zamyatin, author of “We”, a dystopian sci-fi novel written in the 1920’s, that I first read in college. It mentioned that he may have been a synesthete, a term heretofore unknown to me. In reading the entry, it started to sound somewhat famliar to me, as though I may have a form of the…condition?…disorder?…illness? Then the thought occured, why not ask someone who would know for sure!? Since about the age of about four or five, when the world of reading, writing, and literacy became a part of my young little world, I have had, for some reason unbeknownst to myself, very definite ideas as to the gender of individual letters and numbers, days of the week, months of the year, and colours. Masculine: B,C,D,E,G,I,J,K,L,O,Q,T,U, and X. 1,3,6,8,9, and 0. Tuesday, Thursday, Friday, and Saturday. January, June, July, October, and December. Green, Blue, Brown, Black, Gold, and Silver. Feminine: A,F,H,M,N,P,R,S,V,W,Y, and Z. 2,4,5, and 7. Sunday, Monday, and Wednesday. February, March, April, May, August, September, and November. Red, Orange, Yellow, Violet and White. In addition, I have always attributed certain personality traits and relationships between some letters and some days of the week. For instance, I,J,K,L are all brothers, but J,K, and L are older than I, which is also the younger brother of H, which is also the younger sister of J,K, and L. P is about the same age roughly as Q, but Q is much weaker, and is dependent on the much more strong and vigourous P. R is the very strong, dependable, and reliable adult daughter of S and T, and U is the less responsible, but gregarious younger brother of R. Tuesday is the “pampered prince” little brother of Monday and Wednesday. I don’t have the faintest notion how these ideas developed in my little brain, but even now, at the age of 60, they persist, and are the same as when I was a pre-schooler…55 or 56 years later! In my life, I may have disclosed this to maybe a half-dozen people that I have known, including only my second wife (but not the first). I have always gotten the suspicious “askance” look, as if I had related abduction by a UFO, and a trip to the planet Zongo! But now, six decades after birth, I may have a name for this! I am NOT alone! I am an out-of-the-closet Synesthete!!! I may even log on to Facebook, and announce it to the world, or at least my little corner of it!

    • Hahaha Larry…ive always thought of Tuesday the a princy type…although my Monday is like a dont care character and Thursday a tough athletic one…my months are like in linear arrengement all in black and white with like spots of other colours: 2007 has like spilling blackish grey colour on the seven…2010 and 2013 have bright yellow spots on them and 2012 has a shed of navy blue with grey edges…words like The for instance is like a dominant ruler of the others….’what’ is like a wheasle with a long mustuche as in the ‘n’ part of the ‘h’ aand also has a green hat….yeah i know and am not alone either…what a relief and also kinda cool

  20. I have to say that those tests aren’t immediately recognizable to people who associate color. That’s usually for people who project.
    Not to mention, to me, 2’s and 5’s are the same color. (2’s are a darker shade of blue, 5’s are a lighter shade of blue.) So for me it takes a while.

  21. I can taste numbers. Not automatically, but when I eat, for example, spaghetti, I cannot stop thinking of the number 180

  22. I can smell pictures, or smell the scent of food, flowers, industry, even body odor. It is interesting watching tv as I often smell the commercials.

  23. Is there some connection to this same thing when looking at paintings ? As I can taste colors as good or pleasing flavors or bad flavors dependent on the color. The colors dont have to be bright to have flavor they can be very bland or bold and have a flavor.

    • Hi. I can taste colours too. I haven’t found much about that. Bright yellow is sour and sharp. Dark green is bitter and sweet. Orange is chocolaty.

  24. When I hear someone passing gas I totally see a shape. I know that sounds very funny, but it’s true.

  25. I taste and smell images, drawings and colors. I can’t find anyone else with this particular form of synesthesia except my mother who does it with smell but not taste.

  26. I taste colors and smells and smells and taste have colors. Like bear meat is #882D17. It is such a unique taste and mouthfeel and color, I cant described it any other way, but I tell ppl this and some get it, some don’t. I like cooking because to me it is like painting with smell and taste comming together thru colors… I like red foods and those that are green-blue thru deep violet . Orange red thru yellow color foods annoy me, and I don’t like their taste or smell at all. Its usually what I would call chemically, i grew up by many chemical factories and refineries, and organic compounds they released had these colors. My dad also smelled colors, and he loved it as a chemist to smell molecules and compounds and enjoy their colors.

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