Synesthesia is a neurological condition in which stimulation of one sensory or cognitive pathway (for example, hearing) leads to automatic, involuntary experiences in a second sensory or cognitive pathway (such as vision). Simply put, when one sense is activated, another unrelated sense is activated at the same time. This may, for instance, take the form of hearing music and simultaneously sensing the sound as swirls or patterns of color. Since synesthesia can involve any combination of the senses, there may be as many as 60 to 80 subtypes, but not all have been documented or studied, and the cause is unclear. The most commonly seen type is grapheme-color synesthesia, in which individual letters and numbers are associated with specific colors and sometimes colorful patterns. Some synesthetes perceive texture in response to sight, hear sounds in response to smells, or associate shapes with flavors. Many synesthetes have more than one type of synesthesia. It is estimated that approximately 3 to 5 percent of the population has some form of synesthesia, and the condition can run in families.
What Is Synesthesia?
The Sixth Sense of Synesthesia
Sight, smell, taste, touch, sound . . . and synesthesia? Though we’re no closer to discovering (or developing) a true sixth sense, research suggests that synesthesia may confer some sensory enhancements. Some scientists posit, for example, that synesthetes are better at distinguishing between smells as well as between colors. Mirror-touch synesthesia—described as a kind of supercharged empathy, in which someone feels as though they’re being touched if they witness it happening to someone else—appears to come with a special set of considerations. Some, such as an observed advantage in recognizing facial expressions, are benign; others may be burdensome, as in the case of a neurologist who felt intense pressure in his chest when he saw a patient receiving CPR.