Synesthesia: Types, Symptoms, & Causes

What Is Synesthesia?

Synesthesia is when one or more sensory experiences are experienced at the same time in response to a trigger for only one sensory experience. You may hear music that creates images in your mind, or you may see certain words or numbers as a specific color or shape. The brain may route the information through more than one sensory experience, so rather than just hearing a song, you hear it but also taste or feel it.

It is a neurological condition, which means that it affects the nervous system. This happens because the different senses are connected in an involuntary way. Someone who experiences a specific taste when hearing music, for example, experiences this involuntarily.¹

Synesthesia can be associated with increased cognitive abilities, as well as creative outlets. Those with this condition can sometimes be able to remember information and complete cognitive tasks that those without this condition can not complete.¹

How Does Synesthesia Work?

Synesthesia works by giving input through more than one of the five senses of touch, sight, smell, sound, and taste. When someone with synesthesia receives information through one or these five senses, their brain can mediate more than one sense.

Synesthesia works in the order of:

• Detection: The brain picks up sensory input from one of the five senses, either sound, smell, temperature change, or something else.
• Signaling: The sense is sent to the brain, and the brain interprets it. For example, stepping on something sharp or seeing something bright will send signals to the brain about what is being felt or seen.
• Processing: Next, the brain interprets this information and processes it for you. Seeing a brightly colored object has no meaning until your brain tells you that this is a traffic cone, for example, which has a cautionary meaning once processed by your brain.

Primary & Secondary Effect

The brain of someone with synesthesia processes senses with two main steps, primary and secondary. The senses will send information to the brain about what they are experiencing, and then the brain interprets that information to create meaning.

One way to think about synesthesia includes:

• Primary effect: The immediate sensory input is the primary effect: the feel of something you touch, how something looks or smells, for example.
• Secondary effect: The secondary effect is when the individual may taste something bitter when they see the word “exit” even though they have not put anything in their mouth.

How Many Forms Of Synesthesia Are There?

There are at least 60 known forms of synesthesia.² Although this condition has been around for centuries, it has only recently been studied by medical professionals and researchers.³ Some of the most common forms involve the major senses of sight, hearing, and touch and a pairing of these three senses.

Some pairings of three senses common in synesthesia include:

• Sight: Shapes, patterns, and colors
• Hearing: Tempo, rhythm, volume, and pitch
• Touch: Textures, pressure, temperatures.

Common Forms Of Synesthesia

There are many different types of synesthesia depending on which combination of senses the person experiences.² One of the most common forms is sound to color synesthesia, which is when certain sounds cause the person to think about or see specific colors or shapes. However, there are many different types other than this. In fact, researchers are unsure how many forms of synesthesia there actually are.⁴

Auditory-Tactile Synesthesia

Auditory-tactile synesthesia is when certain sounds will evoke specific tactile feelings. For example, hearing the sound of music will cause the person to experience pressure or a feeling of softness.

Day-Color Synesthesia

Day-color synesthesia is when someone associates each day of the week with a specific color. For example, Tuesday is seen as blue, or Friday is seen as pink. The specific color associated with the day might stay constant throughout the person’s life. This means that Friday will be seen as pink, for example, even decades later.

Grapheme-Color Synesthesia

Some people are able to see colors at the same time as numbers. This form of synesthesia is when specific numbers or letters are experienced along with specific colors that they represent. For example, the number 3 may evoke the color green.⁵

Hearing-Motion Synesthesia

Hearing-motion synesthesia is where individuals will receive auditory input at the same time as seeing motion. For example, they may hear a loud smacking sound when seeing someone walking or running.⁴

Mirror-Touch Synesthesia

When someone is able to physically experience the sensations that they are watching happen to someone else they have mirror-touch synesthesia. For example, they are able to feel the touch of someone hugging or even hurting another person.⁴

Time-Space Synesthesia

When someone is able to visualize large mappings of numbers, dates, or other information, this is time-space synesthesia. The person’s brain is able to visualize the information in a specific way, allowing them to remember or visualize large amounts of information such as calendar dates or large numbers.

Visualized Sensations

Visualized sensations is a form of synesthesia where someone is able to experience visual stimuli at the same time as experiencing physical sensations. For example, they may experience a specific color or shape when shaking someone’s hand or when petting a cat.

Can Synesthesia Have Different Levels Of Intensity?

Like all neurodiversity, synesthesia is experienced differently among all people. Experiences will vary in terms of intensity, as well as duration of experiences of stimuli. While experiences will vary, synesthesia might be stable over the person’s lifetime, so if they see the color green when they hear the word “chair,” this same experience will happen a decade later.⁶

Possible Causes Of Synesthesia

Synesthesia is thought of as having genetic and neurological components.⁷ This means that scientists and medical personnel have seen a genetic link for this condition, and that it often develops in childhood.

While there are some other factors that can lead to synesthesia, such as substance use or changes within the brain, these are more rare and inconsistent than genetic-linked synesthesia.

Developmental Synesthesia

Developmental synesthesia is a nuerodivergency. There is a strong link between synesthesia and autism, which is another neurodivergent condition that is developed in infancy or childhood.⁴

The main element of developmental synesthesia is that it is likely to remain consistent and stagnant, or unchanging, throughout the person’s life. Unlike other forms of synesthesia that may be brought on by substances or brain changes, for example, developmental synesthesia will remain mostly unchanging.^{4, 6}

Acquired Synesthesia

When someone experiences changes to the brain, such as through brain damage or a traumatic brain injury, they can develop acquired synesthesia.

It has also been found that some of the changes that occur in the brain from substance use can also provoke acquired synesthesia.¹¹

Drug-Induced Synesthesia

Drug-induced synesthesia is also thought of as acquired synesthesia.¹¹ Because of their effect on the brain, there are specific drugs, especially hallucinogens, that can induce synesthesia.⁸ Some common ones are ketamine, MDMA, Peyote, and LSD.

Please do research and use caution before using any drugs or substances that have the ability to affect the mind or brain, due to dangers and risks associated. Drug dosing should always be under the support and care of a licensed medical professional for safety.

Some examples of drugs that induce synesthesia include:⁸

• LSD
• Peyote
• Marijuana
• MDMA
• Ketamine
• Mescaline
• Psilocybin

How Is Synesthesia Treated?

There is no specific therapeutic or medical modality for treating synesthesia. Many who have this condition advocate for empowering oneself by learning more about it, as well as surrounding yourself with others who are supportive and understanding.

Can Synesthesia Be Prevented?

Due to its genetic component, it is not likely that synesthesia can be prevented if it comes from someone’s development. However, like any neurological condition, substance use can often make the experiences and symptoms worse, so avoiding substance use can help to prevent worsening of the condition.

Can Synesthesia be Learned?

Synesthesia is most commonly developed in childhood, and can be present throughout the person’s life.⁹ However, some people think that they can teach themselves synesthesia traits by learning to associate specific words or sights with specific colors or images.

While there is some evidence that some people can learn this trait,  “Synesthesia is commonly classified as developmental and acquired.”¹¹

How Rare Is Synesthesia?

Synesthesia usually occurs in about 4% of the population, and it is assumed to be inherited due to its genetic basis.⁶

What Is The Rarest Form Of Synesthesia?

The rarest form of synesthesia is thought to be Lexical-gustatory synesthesia, which is when the experience of hearing a word results in tasting a flavor at the same time. For example, hearing the word “car” might taste like mint.¹⁰

Is Synesthesia A Mental Illness?

Synesthesia is not a mental illness, but a neurological condition that is often referred to as a neurodiversity, often resulting from development or acquired due to brain changes.¹¹ Unless this condition causes the person a great deal of stress or impairs their life in some way that makes things difficult, there is no need to seek help. Many synesthesias use their condition as a strength!

When to Seek Professional Help

If your condition is causing you stress or impairing your life in ways that make it difficult to live a fulfilling professional or personal life, it may be time to seek professional support.

An online therapist directory or online therapy platform is a good choice for finding a therapist who specializes in neurodivergent issues such as synesthesia. Similarly, online psychiatrist options are a good choice for finding neurodivergent medication management if this is something you may need.