Synesthesia

What is synesthesia?

Synesthesia is a phenomenon that causes sensory crossovers, such as tasting colors or feeling sounds. Some people describe it as having “wires crossed” in their brain because it activates two or more senses when there’s only a reason for one sense to activate.

Synesthesia isn’t a disease or a medical condition, but it can be a symptom of certain brain-related conditions.

How does synesthesia work?

To understand synesthesia (pronounced “sin-ess-THEE-zh-uh”), it helps to understand how your senses work. Your brain relies on your five main senses — sight, sound, smell, taste or touch — to know what’s happening around you.

That involves the following steps:

1. Detection: Your senses pick up something happening around you. An example would be using your eyes to look at your surroundings or using your ears to listen for certain sounds.
2. Signaling: Your senses send a signal to your brain describing what they’re experiencing. For example, your eyes would describe the colors and shapes of the things you can see nearby, or your ears would send signals that describe how loud a sound is, if it’s high- or low-pitched, etc.
3. Processing: Your brain receives those signals and routes them to a certain area for processing. The area that does the processing connects to areas that help you understand what you’re seeing. Examples of this are recognizing a stop sign by its shape and/or color or recognizing that a sound is a piece of music or someone’s voice.

In short, your senses describe to your brain what they pick up, and your brain creates its own understanding of the world around you from those descriptions. But people with synesthesia experience the processing step differently. Their brains process the same information through two or more brain areas at once. That causes a primary and at least one secondary effect:

• Primary effect: The primary effect is what you experience because of sensory input. An example of this would be hearing sounds and recognizing them as music.
• Secondary effect: People with synesthesia experience a secondary effect (or more than one) that seems like it’s one of their senses working, but there’s no input from that sense that should be causing it. An example of this would be seeing colors because you hear music.

Visual synesthesia can also happen in different ways. Some people experience visual synesthesia like a “projection,” meaning their brain directly combines the secondary effect into their sense of sight. That causes them to experience it as if they actually see it. Other people have an “internal screen” effect. They can automatically picture it in their head but don’t experience it as if they were seeing it directly.

How many different forms of synesthesia are there?

While you have five main senses, there are many different things you can identify with each sense. These are perception abilities. Some examples include:

• Sight: Colors, patterns, textures, shapes.
• Hearing: Volume, pitch, frequency.
• Touch: Temperatures, pressure, textures, vibrations, pain.

Some perception abilities involve more than one sense, like balance. Your perception abilities can also involve concepts you understand using your senses, such as time, numbers and language.

Because there are so many possible combinations between your senses and perception abilities, researchers can identify at least 60 different forms of synesthesia. Some experts estimate there are more than 150 different forms. This is also why many people with synesthesia have it but don’t know what it is or that it’s unusual.

Some forms of synesthesia are better known or are more common. These include:

• Auditory-tactile synesthesia.
• Day-color synesthesia.
• Grapheme-color synesthesia.
• Hearing-motion synesthesia.
• Mirror-touch synesthesia.
• Time-space synesthesia.
• Visualized sensations.

Auditory-tactile synesthesia

This form of synesthesia means that sounds cause you to feel touch-based sensations, such as temperature changes, pressure or pain.

Day-color synesthesia

Some people see or associate certain colors with days of the week. This is one of the more common forms of synesthesia.

Grapheme-color synesthesia

“Grapheme” is the word for the smallest part of a written language, like a letter, number or symbol. Some people see different graphemes with specific colors. People who experience visual synesthesia’s projection effect often see graphemes as different colors.

Hearing-motion synesthesia

Some people experience sounds related to seeing things moving. An example of this would be a person hearing a “whoosh” sound when watching something go past them.

Mirror-touch synesthesia

Mirror-touch synesthesia is when you see something happen to someone else and physically feel it, too. It works similarly to the reflexive cringe you might have if you see someone trip and face-plant in front of you. However, the effect is much stronger.

Some people can watch another person being touched on the arm or hand and they also feel it. Other people can actually feel pain that others describe or pain from visible injuries. This form is more likely to be disruptive if it causes you to feel pain as a secondary effect.

Sound-color synesthesia

Sound-color synesthesia is where you see specific colors when you hear certain sounds. It tends to be specific to certain sounds or music. Musicians and artists often describe having this form.

Time-space synesthesia

This is a form of synesthesia where you visualize things in a very specific way. People who have this form of synesthesia often “see” sequences with specific patterns or forms. An example of this is visualizing a calendar or a string of numbers in a certain way. Some people can mentally “map” these out in vivid or detailed ways.

Can synesthesia have different levels of intensity?

Yes, synesthesia can affect people differently. Some people may only experience synesthesia under certain circumstances. Others may experience synesthesia for many reasons, or they might experience more than one secondary effect.

In severe cases, synesthesia can be strong enough to affect your ability to concentrate or focus. Fortunately, this is rare. Synesthesia is usually short-lived, so it’s usually not disruptive to this degree. People who do have it to this extent can usually learn to manage these secondary effects.

What are the most common causes of synesthesia?

Experts don’t fully understand why synesthesia happens. But they do know there are three main types of it:

• Developmental (sometimes called “genuine” or “constitutional”).
• Acquired.
• Drug-induced.

Developmental synesthesia

People who have developmental synesthesia are “neurodivergent.” That means their brain developed and works in a way that’s different from “neurotypical” people, whose brains developed and work as expected.

Experts can’t yet fully explain why this happens, but they suspect it may involve multiple factors:

• Brain development: There’s some evidence that everyone has synesthesia very early in life and that it’s part of the brain’s natural development. If that’s the case, that means it fades for most people, which is why only a small percentage of adults have it.
• Brain structure: People with synesthesia seem to have more connections between different brain areas. That might explain why multiple brain areas activate from one type of sensory input. It also might be a factor in why the rate of synesthesia in people with autism spectrum disorder (ASD) is at least triple the rate in people without ASD.
• Genetics: Synesthesia seems to run in families. However, the form of synesthesia can vary from person to person, which indicates that this isn’t something that people learn from family members.

Acquired synesthesia

Some people can “acquire” synesthesia because of damage to their brain. Experts suspect this type of synesthesia happens because connections within your brain can change and evolve as your brain recovers from an injury.

But some subtle differences set this type of synesthesia apart:

• It’s less consistent. People with acquired synesthesia may not experience it as often as people who’ve had it all their life. Some people may only experience it under very specific circumstances, or it might go away over time.
• Certain primary effects can’t cause it. Unlike developmental synesthesia, music doesn’t cause synesthesia if someone has the acquired type.
• Secondary effects are simple and short-lived. Developmental synesthesia effects can be longer-lasting, and they can shift and change to follow along with whatever causes them. Acquired synesthesia effects are brief, simple and don’t follow or shift with changes in what causes them.

Drug-induced synesthesia

Nonmedical use of certain drugs, especially hallucinogens (drugs that cause pseudohallucinations and, very rarely, hallucinations), can sometimes cause synesthesia. This is especially the case at higher doses. These drugs, also known as “psychedelics,” include:

• Dimethyltryptamine (also known as “DMT”).
• LSD (also known as “acid”).
• Peyote (including mescaline, a substance derived from peyote).
• Psilocybin (sometimes known as “magic mushrooms,” “psychedelic mushrooms” or just “shrooms”).

Like acquired synesthesia, there are some differences in how drug-induced synesthesia typically affects people. These include:

• They’re emotion dependent. Your emotional state affects if and how you experience synesthesia.
• It can alter what you perceive. Developmental and acquired synesthesia may affect how you experience something, but they don’t change what you experience. Drug-induced synesthesia can cause hallucinations, which can change what you experience.
• It’s not automatic. You can sometimes minimize or stop drug-induced synesthesia by focusing on specific things or changing certain things in your environment (such as lighting).

How is synesthesia treated?

Developmental and acquired synesthesia don’t need treatment. In rare cases, some people may experience effects they don’t like, but they can learn to manage or minimize these effects.

Drug-induced synesthesia may happen at higher doses. That might indicate that a person needs treatment for an overdose of those drugs. However, the treatment can vary depending on the drug in question. Generally, the treatments for these are supportive, helping minimize other more serious symptoms such as seizures or agitation.

Can synesthesia be prevented?

The developmental and acquired types of synesthesia aren’t preventable. The only preventable form is drug-induced synesthesia. Drugs that can cause it are illegal in many places, but there are exceptions for religious or traditional uses. Limiting your exposure to or intake of these drugs in those situations can make it less likely that you’ll experience drug-induced synesthesia.

Is synesthesia something that happens naturally, or is it learnable?

Scientists and researchers have worked to describe and understand synesthesia since the 1800s, but skepticism about this was also very common. It wasn’t until the 1990s that imaging technologies like functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) allowed scientists to see activity in specific brain areas. Those technologies were key in confirming that synesthesia is real.

But research shows synesthesia often has a learned component. Some examples of this are learning the alphabet, counting and numbers, or the names of days and months of the year. And there’s evidence that synesthesia may be something people develop very early in life to help themselves learn and retain information.

Research also shows you can “train” yourself to have a synesthesia-like response with practice. But the effect is temporary and can fade if you don’t use it. It’s also not as fast or as strong as someone who experiences synesthesia naturally.

How rare is synesthesia?

Synesthesia isn’t common, but it isn’t rare, either. Experts estimate at least 4% of people worldwide experience it. However, that number may be higher because there are so many possible forms of synesthesia. Some experts estimate that certain forms of synesthesia — especially time-space synesthesia — may affect as many as 1 in 8 people. It’s also possible that synesthesia is so natural for some people that they experience it and don’t realize what it is.

What is the rarest synesthesia?

Experts know that some forms of synesthesia are rare, but there’s no way to know which form is rarest. A major reason for this is that many people have synesthesia and don’t know what it is or think that everyone experiences it. But the available research shows that taste- and smell-based forms of synesthesia are less common, while sight-, hearing- and touch-based forms of synesthesia are more common.

Are there advantages to having synesthesia?

Research shows that synesthesia has benefits. People with it often have better memory abilities relating to the form of synesthesia they have. They also tend to score higher on tests that measure intelligence.

Synesthesia also has clear ties to creativity, and people with synesthesia are more likely to choose creative- or art-based careers. Sound-color synesthesia is something that many music artists have. Famous music artists with synesthesia include Beyoncé, Duke Ellington, Billy Joel and Mary J. Blige.

Is synesthesia a mental illness?

No, synesthesia isn’t a mental health condition. In some cases, it can be a symptom of certain medical issues, but this is rare.

Can people who can’t use certain senses still have synesthesia?

Yes, synesthesia can happen in people with certain sensory problems. There are confirmed cases of synesthesia in people who developed blindness later in life and in at least one person with congenital blindness (meaning they had blindness when they were born). There’s also research on one person with synesthesia and a color vision problem who could still experience a color their eyes couldn’t actually see.

A note from Cleveland Clinic

Synesthesia is a phenomenon that causes sensory crossovers, which means you experience the world with two or more senses or perception abilities that aren’t otherwise related. Research shows synesthesia involves real differences in how your brain works, especially when it starts in childhood. It isn’t a medical condition, but it can be a symptom of certain issues when it happens after childhood.

People with synesthesia tend to be more intelligent, creative and have better memory abilities. If you think you have synesthesia, there’s no shortage of books, online communities and other resources to help you explore it. They can help you better understand the way your brain works. That’s the first step to using this ability in a way that enriches and improves your life.