The color purple tastes like a pear. The number two appears as a shade of green. The letter R sounds like a piano playing a high C. Can you imagine that? These are all real possibilities for people with synesthesia, which the American Psychiatric Association refers to as “everyday fantasia.”
For a synesthete—the name given to those with this condition—two unrelated senses activate at the same time. For example, a person might hear music and sense patterns of color at the same time or see a number and experience an accompanying smell. Not surprisingly, synesthesia is an incredibly rare condition, estimated to affect just three to five percent of the population, but there are a few notable folks who reportedly had it, such as writer Vladimir Nabokov (Lolita), who was outspoken about his synesthesia, as well as inventor Nikolas Tesla.
Technically, synesthesia can combine any of the senses, meaning there could be as many as 60 to 80 subtypes. The most common varieties, though, are grapheme-color (in which letters and numbers are associated with specific colors or colorful patterns) and color-auditory (certain sounds are linked to specific colors or textures). For the vast majority of people, how the connections present to a synesthete are permanent—for example, if the letter A is linked to an emerald green hue, it will always appear as that color. How the link between the two senses appears can vary from synesthete to synesthete. For some, the related senses appear only in their mind’s eye, but others might actually see visions of color or patterns outside their body, usually within arm’s reach.
Researchers still don’t understand synesthesia fully. More than a century ago, researchers considered it to be some sort of “crossed wire” in the brain. Current research has created theories that include the idea that irregular neural connections broke down the normal boundaries between senses, as well as another that posits that humans are born as synesthetes but brain growth prunes the connections between the senses. There’s a good chance that the number of synesthetes in the world is underreported—children don’t often realize that these sensory connections are atypical and get berated, patronized, or ridiculed for talking about it.
Unlike many health conditions, synesthesia is most often considered a bonus sense rather than a burden. However, there is a risk of sensory overload and overstimulation. After all, just think about how overwhelming it is when confronted with a situation that demands multiple senses all at once, and then consider living life like that constantly—can you imagine that?
