Synesthesia is a neurological condition in which information meant to stimulate one of your senses stimulates several of your senses. People who have synesthesia are called synesthetes.
The word “synesthesia” comes from the Greek words: “synth” (which means “together”) and “ethesia” (which means “perception). Synesthetes can often “see” music as colors when they hear it, and “taste” textures like “round” or “pointy” when they eat foods.
Researchers are still unsure about how common synesthesia is. One 2006 study proposed that it occurs in 2 to 4 % of the population.
If you have synesthesia, you might notice that your senses tend to intertwine, giving your perceptions of the world an additional dimension. Perhaps every time you bite into a food, you also feel its geometric shape: round, sharp, or square.
Maybe when you’re feeling emotional over a person you love, you can close your eyes and see certain colors playing at your field of vision.
You may be reading these words with a series of accompanying voices in your head, characterizing each sentence with an identity of its own as you would a person you were speaking to on the street.
All these experiences are examples of synesthesia.
People who experience synesthesia are usually born with it or develop it very early in childhood. Each one of your five senses stimulate a different area of your brain. Looking at a bright neon yellow wall, for example, will light up the primary visual cortex, at the rear of your brain. If you have synesthesia, you may also feel like you can taste the color of the wall while you look at it.
So not only will your primary visual cortex be stimulated by the color, your parietal lobe, which tells you what something tastes like, is stimulated, too. That’s why researchers believe that people who have synesthesia have a high level of interconnectedness between the parts of the brain that are tied to sensory stimulus.
Some substances can cause you to temporarily experience synesthesia. The use of psychedelic drugs can heighten and connect your sensory experiences. Mescaline, psilocybin, and LSD have been studied for their ability to induce this phenomenon. But other stimulants, like cannabis, alcohol, and even caffeine, have also been shown to cause temporary synesthesia.
Source: Watson, K. (2018)