What is synesthesia?
Synesthesia (sin-ess-THEE-zhuh) is a neurological condition that impacts an individual’s senses. When one sense activates, a second sense activates at the same time. For some, certain sounds may cause the person to see a certain color. For others, some words may bring up a specific taste.
Synesthesia, which means “to perceive together,” is not an illness. It is simply a different way of experiencing the world because of how the brain automatically works. You can’t control it.
What causes synesthesia?
There are three steps the brain takes when using any of the five senses.
Detection – A sensory event (like a sound) causes the body to respond (the ears perk up to listen).
Signaling – Sensory data (the sound waves) travels to the brain for processing.
Processing – The brain interprets the information into what we recognize as a sound.
These steps produce what is called a primary effect — the interpretation of one sense at a time. In this case, the brain recognizes a sound as someone talking.
In individuals with synesthesia (known as “synesthetes”), a secondary effect also takes place at the same time. While the only sensory input is the sound, the brain sees a color along with hearing the voice. This happens even though there has been no sensory input for the color.
These secondary effects can happen with any of the five senses.
Little is known about what causes synesthesia. However, there are three theories that have been established about its origins.
Developmental synesthesia
Those with developmental synesthesia grew up with the condition. Their brains formed differently from “typical” brains. Because of this difference, developmental synesthetes are categorized as neurodivergent.
There are a few theories about how this type of synesthesia occurs. Genetics may cause the brain to develop more connections between different areas. This increases the likelihood that multiple parts will activate at the same time.
There is evidence that it runs in families. However, each member of the family may experience different kinds of synesthesia.
Its root in brain development may explain the link between synesthesia and autism spectrum disorder (ASD). The rates of synesthesia are three times higher in those with ASD than those without.
Acquired synesthesia
Brain damage in some individuals may cause the development of synesthesia. This is known as acquired synesthesia. The physical trauma of a brain injury can reorganize neural connections in the brain. In very rare occurrences, this may cause senses to link together.
Acquired synesthesia is distinct from developmental synesthesia in a few ways. For one, it may not be as consistent and may even go away over time. Synesthetic episodes are also shorter than they are for those with developmental synesthesia.
Drug-induced synesthesia
Some individuals have experienced synesthesia after taking certain drugs designated as hallucinogens. These include drugs such as:
Dimethyltryptamine
LSD
Peyote
Psilocybin (mushrooms)
Drug-induced synesthesia only occurs with high doses of these drugs. It is not an automatic or controllable outcome.
