What is Synesthesia?

by | May 13, 2020


Synesthesia is a condition that results in the blending of the senses: the stimulation of one sense triggers an experience in another sense. According to the American Psychological Association, “some synesthetes hear, smell, taste or feel pain in color. Others taste shapes, and still others perceive written digits, letters and words in color. Some, who possess what researchers call ‘conceptual synesthesia,’ see abstract concepts, such as units of time or mathematical operations, as shapes projected either internally or in the space around them. And many synesthetes experience more than one form of the condition.”

Examples of synesthesia include:

  • Perceiving numbers or letters as representing different colors. For instance, seeing the number 9 as red and the number 15 as green. This is the most common type of synesthesia and is called grapheme-color synesthesia.
  • Foods tasting like different colors. Beef might taste blue and chili might be green.
  • Different sounds may create a sensation of color. Hearing a guitar may also trigger the sensation of seeing green.
  • Colors may be associated with sounds. Seeing blue may cause the sound of drums.
  • Shapes may generate tastes. A pentagon may taste like chicken.
  • Scents or hearing music may cause particular sensations on the skin. The sound of violins may cause a tickle on the back of the neck.
  • Smells might have a color to them. Flowers may smell yellow.

Synesthesia is not a hallucination. Synesthetes actually experience both senses even though just one was physically triggered. The condition appears to be biological and unlearned.

The mechanism that creates synesthesia is unknown. According to Scientific American, “synesthesia might arise from some kind of anomalous cross-wiring between brain areas that are normally segregated in nonsynesthetic individuals. For grapheme-color synesthesia, there may be cross-wiring between digit and letter processing areas and color processing areas in the visual cortex, which occupy neighboring regions of the human brain.” There appears to be a genetic component as synesthesia tends to run in families.

Synesthesia may be as rare as one person in 2,000 having the condition or as common as 4% of the population being synesthetes. Because synesthesia doesn’t present a problem for the vast majority of people who have it, they don’t seek treatment of it so it’s difficult to know how many people have it. Many with synesthesia consider it a “bonus sense” — like having a sixth sense. According to a synesthesia researcher at University of Cambridge, “If you ask synesthetes if they’d wish to be rid of it, they almost always say no. For them, it feels like that’s what normal experience is like. To have that taken away would make them feel like they were being deprived of one sense.”

Many thanks to my 10-year old cousin Jones for suggesting this topic to me. I had never heard of this condition until he clued me in.


  1. Numbers evoke a wide range of emotional responses within me that are specific to each particular number. For instance 9 might = happy, 3=sad, 8=uneasy etc and there are varying degrees of the strength of emotional responses. As with emotions, which can be very complex, usually the emotion I feel from numbers are much more complex than just happy or sad and are blends of many feelings. They each have their own unique emotional identity within me though. Is this a form of synesthesia?

  2. I read a wonderful book on this and other fascinating conditions like it: “Unthinkable,” by Helen Thomson. Highly recommended!

  3. I have synesthesia, but didn’t know it until I was an adult. Mine is a bit different in that I associate genders and personalities with numbers and letters and sometimes objects. I thought everyone did until I said something to a friend in college and she was like whoa….what? It probably wasn’t until a decade later that another friend who also has it told me it was synesthesia.


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