User:Mr. Ibrahem/Synesthesia

Synesthesia is a phenomenon in which stimulation of one sensory or cognitive pathway also leads to involuntary experiences in another sensory or cognitive pathway. The most common stimulations are letters, numbers, or words; and the most common experiences are colors or textures. Other types may involve days, music, taste, or people. People may have more than one type.

The cause is unclear. Cases may develop earlier in life or be acquired following a precipitating event. Risk factors include family history, sensory loss such as blindness, and substances like lysergic acid diethylamide (LSD). About 40% of cases have a first-degree relative who is affected. The underlying mechanism may involve decreased neuronal inhibition or decreased pruning of nerve connections. There remains ongoing discussion on to how best define the condition.

Between 2% and 20% of people are affected to some degree. Males and females appear to be affected with similar frequency. The condition may result in benefits in cognitive processing such as creative ability. Some have used it to help with memorization.

The earliest recorded case may be from 1690 by philosopher John Locke, who described a blind man who experienced the color scarlet when he heard the sound of a trumpet. However, some dispute if what Locke described was an actual instance of the condition or a metaphor. The first medical account is attributed to German physician Georg Tobias Ludwig Sachs in 1812. The term is from the Ancient Greek σύν syn, meaning "together", and αἴσθησις aisthēsis, meaning "sensation". Those who have a long term history of such experiences are known as synesthetes.