Synesthesia

The United States Population makes up 4.2% of the total world population. That’s around 342 million people which when you look at it like that, seems like a lot. 

Let’s add another 0.2% to that. Approximately 16.6 million people. 

In total, this is above 350 million people. That’s 1 in 23 people.

Now, what do all these values mean?

1 in 23 people you meet, has some form of fully-fledged synesthesia, defined as the brain confusing multiple unrelated senses, causing you to experience more than one sense simultaneously.

How do people perceive senses?

Typically, the brain follows three steps. Detection, signaling, and processing. Detection is when the senses – hearing, sight, touch, taste, and smell – pick up your surroundings. Next, signaling. The organs related to these senses send signals to your brain, telling it what you are experiencing. Then, the brain processes these signals, allowing you to become aware of what is happening. 

Here’s an example. 

Your nose picks up the smell of something burning on the stove. Then, your nose sends signals to the brain. Finally, the brain processes the signals and lets you know that there is something burning. 

How does synesthesia work then?

People with synesthesia have different processing steps. Instead of the information being processed with a singular part of the brain, it goes through two or more areas of the brain at the same time, causing multiple effects. 

For example, chromesthesia. When people with chromesthesia hear a sound, they recognize it for whatever it may be, but in addition to processing the sound, they also see a color due to the sound, causing chromesthesia to also be known as sound-to-color synesthesia. 

Chromesthesia, like any other type of synesthesia, is not interpreted exactly the same for all people with the condition. Some experience the color as if they are actually seeing it, while others have a different perception known as the “internal screen” effect. The color is seen “internally” and in the head, rather than an actual sighting. 

How many kinds of synesthesia are there?

For each sense, the brain can identify many different things. Sight leads to color, pattern, texture, and shape; hearing leads to volume pitch and frequency; and touch leads to temperature, pressure, texture, vibration, and pain. Due to the many combinations between the senses, researchers estimate that there could be over 150 forms of synesthesia, however only 60 are formally identified. 

Some forms are chromesthesia, previously mentioned; auditory-tactile synesthesia, hearing sounds leads to feeling touch-based sensations; hearing-motion synesthesia, people hear sounds in relation to seeing moving objects; and day-color synesthesia, certain colors are associated with each day of the week.

Why does synesthesia occur?

While experts don’t fully understand why synesthesia happens, they have categorized it into three specific categories. 

Firstly, developmental synesthesia. Those with developmental synesthesia are “neurodivergent”, meaning that their brain developed and works in a way that is separate from people whose brains developed “neurotypically”. The factors that may lead to developmental synesthesia are brain development, brain structure, and genetics. 

There is existing evidence that suggests that early on in life, all people have synesthesia, meaning it must fade for all people, causing only a small percentage of people to have it. The small percentage of people who do have it, have more connections between their brain areas, which could explain why multiple brain areas activate due to one type of sensory input. In addition, it could explain why people with autism spectrum disorder have triple the rate of synesthesia in comparison to people without autism spectrum disorder. 

Genetics wise, synesthesia appears to run in families, however since there is variation from person to person, it implies that it is not learned, but rather genetically based.

Secondly, there is acquired synesthesia. Those who acquire synesthesia typically have this occur due to damage in the brain. Experts who have studied the topic believe that it is because the connections within the brain change and evolve as the brain recovers from injury.  

However, acquired synesthesia tends to be different from developmental synesthesia. Acquired synesthesia is typical;ly less consistent and more circumstantial than developmental synesthesia and can also also disappear with time. 

Finally, there is drug-induced synesthesia. Nonmedical usage of certain drugs in certain amounts can cause synesthesia. These drugs are known as psychedelics, including LSD, dimethyltryptamine, peyote, and psilocybin. 

Drug-induced synesthesia is emotion dependent and naturally, only occurs as a result of taking the drug, not organically. 

Does synesthesia require prevention or treatment?

Aside from drug-induced synesthesia, synesthesia is not preventable and doesn’t require treatment, however some forms of synesthesia can be managed or minimized if the effects are disliked.