While many people have good taste in music, music literally tastes good to a few; the sounds may trigger the taste of chocolate or chicken in their mouths. Others see specific colors when they hear specific notes, e.g an “F” may produce yellow in their mind’s eye, while a “C” could literally give them “the blues”. The sound of a spoken word could feel like the touch of a feather.
The phenomenon is called “synesthesia” ( “sin-es-THEEZ-ia), i.e. a neurological condition that causes two or more senses to blend, and the people who experience it are called “synesthetes” ( “SIN-es-theets). The cause of synesthesia is unknown. Even so, researchers have found that it tends to be hereditary, and have connected several genetic markers to it; the same markers have also been linked to autism and epilepsy, which might explain why many autistic people are also synesthetes.
An estimated 2 to 5 percent of the population are synesthetes, according to the Encyclopedia Britannica. But, Scientific American thinks synesthesia affects between 1 in 20,000 to 1 in 200 people. In other words (and/or other numbers), even the prevalence of the condition is a mystery.
However, a new study from the City University of London has reportedly found a type of synesthesia that is possibly much more common than most. These researchers have apparently discovered that up to one in five people can “hear” the sound of flashing lights, even when the lights are absolutely silent. Many of those who reported hearing the lights also experienced other unusual auditory phenomena, such as tinnitus (ringing ears) and getting a song stuck in their head (also known as an “earworm”).
In a press release about the research, lead author Dr. Elliot Freeman said, “Some people hear what they see. Car indicator lights, flashing neon shop signs, and people’s movements as they walk may all trigger an auditory sensation. We think that these sensations may sometimes reflect leakage of information from visual parts of the brain into areas that are more usually devoted to hearing.”
While there are still far more questions than answers about synesthesia, scientists have determined that it is not the same thing as hallucination. Hallucinations don’t have predictable patterns, but synesthetic events happen the same way each time for the person who experiences them. For example, an individual may always taste an orange every time he or she sees the number 7, or smell a rose whenever a dog barks. But, the experiences are highly individualized, too; e.g. the number 7 might trigger the sound of a galloping horse in a different synesthete. Also, the sensations aren’t necessarily connected to a meaning, so reading “7” can provoke a different reaction in the same person than reading “seven”.
Scientists are sure that synesthesia is an actual neurological condition, “crossed wires” in the brain rather than a learned response to certain stimuli. Neuroscientist David Eagleman describes it as “involuntary, unconscious, and automatic. It’s not somebody making it up. It’s somebody having a genuine perceptual experience.”
Researchers have discovered that women are about six times more likely to be synesthetes as men. Also, some scientists believe that most of us might be born with synesthesia that disappears as we grow up.
The phenomena take many forms, including:
- Grapheme-color synesthesia. In this type, a person’s perception of numbers and letters is associated with colors. Every letter or number is either viewed as physically written in a specific color or visualized as a color in the mind.
- Music-color synesthesia, in which musical notes result in color visualization.
- Tactile-emotion synesthesia, where certain fabrics and textures trigger certain emotions.
- Spatial sequence
- Time units-color
While most synesthetes have one or two versions, a small percentage have up to five. It’s hard to imagine what that must be like.