What is Synesthesia?
Synesthesia is a condition where when a sensory stimulus is presented to one sense (i.e., hearing a word) and a secondary sense is activated (i.e., you see a color when you hear the word), and is present in 2-4% of the population.
Those with the condition are often called synesthetes.
The five main senses are: sight, sound, touch, taste, and smell. Sounds are processed via hearing, touch via physical feeling, odors via smell, and so on.
However, in synesthetes when more than one sense is stimulated at a time, odors can have smells and taste, letters can have consistent colors, sounds can evoke visions, for example.
Causes of Synesthesia:
The cause of synesthesia is not clearly understood. It is believed to have a genetic component, although the specific genes involved remain unclear. Nearly 40% of those who possess synesthesia have a relative with the condition as well.
However, specific forms of synesthesia vary amongst family members suggesting that genes predispose a person to synesthesia but don't regulate the expression of synesthesia.
It has been proposed that synesthesia results from an excess number of neural connections between associated senses, possibly because of decreased neural pruning between regions as a fetus. In basic terms, two senses are crossed in the brain allowing them both to fire at once.
Types of Synesthesia:
Over sixty forms of synesthesia have been reported, though most have not been researched or evaluated at length. What is known is that this condition can combine any two or more senses; hearing and sight, sight and taste, and so on. But the most common is when sounds cause vivid colors, or numbers that cause colors.
- Projector synesthetes perceive colors for letters, or see color when letters or numbers are noted
- Association synesthetes see colors in the mind's eye, meaning they perceive it internally rather than seeing the physical object as color
- Perceptual synesthetes are triggered by sights and sounds
- Conceptual synesthetes perceive based on the abstract such as time, for example each month may be represented by a specific color
With colors, although the colors associated with numbers or sounds may vary among individuals with synesthesia, they remain stable over time for each person.
Risks for Developing Synesthesia:
While it is unclear what causes synesthesia, studies have shown there are several factors that make one more likely to have synesthesia. These factors include:
- Being female – studies indicate as many as eight times more women have synesthesia than men
- Being left-handed – those with synesthesia are more likely to be left-hand dominant
- Having a family history of synesthesia
Symptoms of Synesthesia:
The symptoms of synesthesia are perceptions that are:
- Involuntary - the synesthete does not think about the perception, it just simply occurs to them
- Projected - the perception doesn’t only occur within the mind, instead it is also seen outside of one's body
- Durable - the perception is consistent every time the sense is used (i.e., the letter "q" is orange every time it is seen)
- Generic - one would see colors or lines, for example, in connection to a certain smell, word, sound, but would not see a room full of people and furniture
- Memorable - the secondary perception is often more memorable than the primary, for example if a person associates a specific color with a person's name they may recall the person's name as being that color easier than recalling the actual name
- Emotional - these perceptions may cause emotional reactions, most often pleasant ones, that arise each time the perception is felt
Several traits that synesthetes tend to share include:
- Confusing right and left, north and south, and similar
- A terrible sense of direction or navigation
- Possess an incredible memory
- Experience migraines
- Typically an introvert
- Creative mind, artistically talented
- Ticklish, more so than most
Diagnosis of Synesthesia:
The diagnosis of synesthesia is made when a person takes the "Synesthesia Battery" which is then reviewed by a professional and a diagnosis made if the criteria of perceptions is met.
It is important to note that synesthetes are considered to be neurologically normal, and typically of above average intelligence. The crossed perceptions appear to have little to no impact on standard neurological exams.
Treatment for Synesthesia:
Most patients with synesthesia would argue against treatment for their condition, as treatment would entail reducing or removing one of the senses. Having heightened senses is not typically debilitating, and therefore not something that needs to be corrected. If it begins to affect quality of life, a doctor may be able to assist in seeking treatment to reduce the stimulation of the sense causing the trouble.
For those seeking to know more about their condition, hypnosis has been shown to produce the best results in learning more about how an individual's senses are crossed. Some professionals do warn that synesthesia is similar to a hallucination, but one that persists through the conscious mind. Undergoing hypnosis can help to dig into the dream state where imagery may play into false memories or fabricated perceptions that the conscious mind has never challenged previously.
Additional Resources for Synesthesia:
BBC Horizons - Synesthesia is an episode of a BBC show that follows a woman living with Synesthesia.
Synesthete.org offers a preview and demos of what the Synesthesia Battery looks like.
Synesthesia Test offers information about the condition.
American Psychological Association offers information about the world of synesthesia and how research is being driven to understand it.
Wednesday is Indigo is recommended reading, written by researcher Richard E Cytowic, a leader in Synesthesia about a man with synesthesia (the third generation in his family to have it).