Basics of Synesthesia

Synesthesia is defined as a rare experience where one property of a stimulus evokes a second experience not associated with the first.

Synesthesia, the legendary ability to see sounds, hear sights, and taste colors, has perplexed mankind for centuries. Some scholars have even found evidence of it in ancient texts, but it has only begun to reveal its secrets in recent years. Throughout this article, you will discover information on the definition, characteristics, and types of synesthesia; explore its causes and pros and cons; learn about famous synesthetes, and have the opportunity to take free tests if you suspect you may have synesthesia yourself.

Synesthesia Definition

Synesthesia Definition

What is synesthesia? According to Frontiers in Psychology, one definition of synesthesia is “a rare experience where one property of a stimulus evokes a second experience not associated with the first.” This medical website defines synesthesia more simply as “a blurring of the senses. For example, certain words taste, or numbers might have colors.” But these are not arbitrary tastes or colors; this article from Frontiers in Psychology specifies that each “stimulus will consistently and involuntarily produce a second concurrent experience” (emphasis added). The article lists these criteria for a genuinely synesthetic experience:

  • The experience must be “automatic” or involuntary; in other words, a synesthete can’t choose whether to have a synesthetic experience or not. It just happens.
  • The stimulus causes the same reaction every time it is perceived. A synesthete who sees blue upon hearing the word “banana” will see the same color every time they hear that word.
  • The experiences have “consistency,” meaning that a certain type of synesthesia reacts to a certain type of sensory input with the same response every time. Thus in a type of synesthesia where letters are seen in color, the synesthete will always see the letters in color rather than, for instance, in textures or flavors.


According to Julia Simner’s 2011 article in the British Journal of Psychology, 61 types of synesthesia are recorded to date. The University of Sussex explains that while there are five recognized senses, you’d expect all possible pairings to number twenty. This is not the case because more than one type can exist for each set of two senses. Chromesthesia pairs the sense of hearing with just one aspect of sight (color). Other kinds of synesthesia may pair the sense of hearing with some other aspect of sight.

Some types of synesthesia are named, while others remain unnamed. Nobody knows what percentage of the world’s population has synesthesia, so there may be many more types that have yet to be discovered or recorded. Here are a few of the types of synesthesia known to science:

Named Types synesthesia

  • Grapheme-color synesthesia: As the name indicates, this form confides graphemes (letters and numbers) with colors. This form is one of the most well-known and well-researched, although not the most frequent.
  • Spatial sequence synesthesia: Some sources consider this not a “true” form of synesthesia since it isn’t technically a merging of two senses. However, it is a very common phenomenon, with some estimating it may affect 20% of the population. In this form of synesthesia, numbers are perceived as having a definite location in space, like an imaginary three-dimensional number line.
  • Chromesthesia, so-called because it involves color, is a form in which individuals experience particular sounds with distinct colors.
  • Auditory-tactile synesthesia is a rare form of synesthesia in which individuals experience certain sounds as being accompanied by (or producing) a tactile sensation.
  • Lexical-gustatory synesthesia: A form in which words cause the synesthete to experience tastes. This form is also rare.

Additional types (according to the University of Sussex)

  • Perceiving color when thinking of days and months
  • Experiencing colors or shapes when hearing musical instruments or musical sounds
  • Experiencing taste when hearing speech
  • Experiencing color produced by a taste
  • Experiencing shapes or colors upon perceiving a smell
  • Experiencing color when touched

Synthesized Synesthesia

Throughout this article, the focus of the discussion is on naturally occurring synesthesia. However, medical professionals can synthesize something akin to a temporary synesthetic response using drugs. Some illegal hallucinogenic drugs have also been known to cause similar phenomena for a short period, although not safely or reliably. In addition, some scientists consider devices that represent sensory information via another sense to fit the definition of “synesthetic” as well (one example given is a laser light show, which “converts sound to sight”).


No one knows exactly why synesthesia occurs, but scientists have discovered that it runs in families and can be hereditary. Recent research has investigated its development and frequency among children in the UK and the USA.

According to the Max Planck Institute for Psycholinguistics of the Netherlands, 2-5% of people who experience synesthesia have been shown to inherit it genetically. However, studies are still in progress regarding which genes are involved. If you have synesthesia and would like to be part of one of these studies, you can do so by taking their questionnaire here.

Pros and Cons of Having Synesthesia

Like any other circumstance in life, synesthesia has both advantages and disadvantages. If you’re curious about whether your synesthete friends have advantages at school or work, look at some of the pros and cons listed here.


  • National Geographic discusses the possibility that synesthesia may be helpful to the creative process. A common belief about synesthesia is that it improves IQ. This is not necessarily the case; however, studies show that “color working memory” may be superior in grapheme-color synesthetes, while “grapheme working memory,” the memory for letters and numbers, does not improve. Since grapheme-color synesthetes see letters and numbers in color, a superior “color working memory” may aid studying.
  • There is a much higher percentage of synesthetes in creative professions (such as music, art, and writing) than in other professions. This may mean synesthesia bestows artistic genius, but it’s more likely the aesthetic pleasure derived from synesthetic experiences (such as seeing beautiful colors every time you hear music) inspires synesthetes to seek out a profession where they can have these experiences regularly.


  • It can be difficult for non-synesthetes to understand and sympathize with the peculiar trials synesthetes face.
  • No two synesthetes are alike, so trying to get together a synesthesia support group may result in having a fierce argument over what color someone’s name is.
  • Misunderstandings: society and science don’t fully understand synesthesia yet, and ignorance propagates myths and stereotypes.
  • Sensory overload: In situations with many sights, sounds, and smells, a synesthete’s brain will continue to respond with different experiences, potentially turning a complicated situation into a truly chaotic one.


Many famous people throughout history have been synethetes. See if you recognize any of the names in this list of synesthesia examples:

Synesthetic Artists:

  • Vincent Van Gogh
  • David Hockney
  • Wassily Kandinsky
  • Vladimir Nabokov said he “[saw] letters in color.”

Synesthetic Musicians:

  • Duke Ellington
  • Franz Liszt
  • György Ligeti
  • Itzhak Perlman
  • Nikolai Rimsky-Korsakov
  • Stevie Wonder
  • Olivier Messiaen

Other Famous Synesthetes:

  • Nikola Tesla, the inventor, made several odd statements regarding his senses and today is generally regarded as a synesthete.
  • Ludwig Wittgenstein, philosopher
  • Richard Feynman, physicist


If you do have synesthesia, you’ve probably already discovered the fact. Still, if not, or if you have a child you suspect may have synesthesia, you can use an online synesthesia test or two to help you figure it out:

  • This free pretest is offered on the Synesthesia Battery website.
  • Another quick, free quiz is available here.

These two don’t measure or label what type of synesthesia you have but predict whether or not you have it at all. If you get positive results, move on to the next level of tests:

  • The Synesthesia Battery has a fairly extensive series of tests available for synesthetes. These include tests for graphemes represented in color, musical notes and chords represented in color, and more.
  • Another test is available from the Cohen Kadosh Labaratory.

If you find out that you have synesthesia, there are many scientific studies (such as the one mentioned above under “Causes”) in which you can take part to help the world learn more about this elusive phenomenon. But whether you’re a synesthete yourself or merely curious, use these free tests (and sources cited throughout the article) to educate yourself and your friends!

More Great Contents