Synesthesia: Definition, Explanation, And More

Medically reviewed by Paige Henry, LMSW, J.D.
Updated May 30, 2024by BetterHelp Editorial Team
Curious about synesthesia?

Synesthesia is a phenomenon that can occur when people experience “extra” or unrelated senses being activated in response to stimuli.

Increased awareness and understanding of synesthesia can help create more empathy for those living with the condition. Read on to learn more about what synesthesia is and the different types of synesthesia one may experience.

What is synesthesia?

Synesthesia is a neurological condition in which the stimulation of one sense, such as hearing a sound, activates an unrelated sense, such as seeing colors.

For example, some people can “see” music. This means that they can hear music as it sounds to others, but they can also visualize the specific sounds based on the auditory stimuli they’re experiencing.

The experience of synesthesia may vary depending on a person’s individual experiences and the type of synesthesia that they are living with. 

There are many different types of synesthesia that one may experience. Understanding the different types can often be the first step to validating your experience if you believe that you are living with synesthesia. 

What causes synesthesia?

At the time of this publication, there is not a singular identified cause of synesthesia. Many people in the scientific community believe that the condition may be caused due to neurons in the brain firing in response to stimuli, potentially triggering synapses in nearby neurons. It may also be genetic, according to some studies.

Scientists believe that an estimated 2-4% of the population may have synesthesia but acknowledge that there could be many more undiagnosed people. New research with functional magnetic resonance imaging (fMRI) suggests that individuals living with synesthesia experience a dramatic increase in the area of the brain responsible for sight when the participant is subjected to certain stimuli. Another test referenced in the linked study showed that sensory receptors might be more active in some individuals, giving them the appearance of an “extra sense.”

Different types of synesthesia

A person who experiences any type of synesthesia can be considered a synesthete. No matter what kind of synesthesia one has, it is generally believed that no two people experience it the same way. Science currently supports the hypothesis that there are two basic forms of synesthesia: associative and projective.

Associative synesthesia

Associative synesthesia can cause those who have it to associate certain colors with numbers, letters, sounds or tastes. They do not smell, feel, or see them in many cases, often simply perceiving their presence. 

For example, some who have this condition may see the letter A written in black ink as blue in their head, but they can still see it in black as well.

To these individuals with associative synesthesia, there can be a connection between the stimuli and the sense that is activated, even if it cannot be seen or explained.


Projective synesthesia

People with projective synesthesia may see shapes, forms, or colors when they hear, smell, or taste something. They may also actually taste, smell, feel, see, or hear things that are supposed to be experienced by a different one of their senses. 

For example, people who live with this form of synesthesia may be able to see a sound or taste a word. For them, the sound of a guitar may cause them to see the color orange. In contrast, those with associative synesthesia might just feel or know that the guitar sounds orange without really “seeing” it.

Researchers have identified over 60 variations of synesthesia. Each variation is generally associated with stimulating a unique set of senses in response to perceived stimuli. 

We’ve summarized a range of synesthesia subtypes below.

Grapheme-color synesthesia

This is considered to be one of the most common variations of synesthesia. Those who live grapheme color synesthesia with the projective subtype may see numbers or letters as certain colors. 

Those with associative synesthesia may perceive that the number or letter is a certain color without seeing it.


Those who have chromesthesia may see colors when they hear certain sounds. For instance, a dog barking may cause the synesthete to see the color green, based on whatever previous association has been stimulated or established. While projective synesthetes might see the color green in real life, associative synesthetes may simply associate that sound with the color.

Spatial sequence synesthesia

Synesthetes living with spatial sequence synesthesia may see numbers at different points in space. For example: A person living with this condition may perceive the number one as a “closer” integer than the number two — but for others, it may be the other way around. 

Another example commonly lies within the year, month, and day format, in which the year 2010 may be to one’s “right,” while Tuesday is “above” your head.

Number form synesthesia

Someone with number form synesthesia can visualize a map of different numbers in a certain order when they think about numbers as a concept. This can be like spatial sequence synesthesia, but those with this condition might see the numbers in order in a line rather than perceiving their set point.

Auditory tactile synesthesia

This type of synesthesia can cause certain sounds to stimulate a sensation in part of your body. In other words, if you have auditory and tactile synesthesia, you may have a link between the sensory connections that dictate your sense of hearing and your sense of touch. 

Mirror-touch synesthesia

Mirror-touch synesthesia can range from being able to feel other people's emotions to experiencing others' pain or another physical feeling they may have — similar to a form of severe empathy. 

For example, if you see someone touch your friend on the back, and you feel a touch on your back even though nobody is there, you may have mirror-touch synesthesia. People with this form of synesthesia can be so affected by other people's feelings that they may isolate themselves to avoid feeling overwhelmed by what others feel. 

Curious about synesthesia?

Treatment for synesthesia

Synesthesia is not a mental health disorder and does not require treatment. Many people living with the condition enjoy the extra sensory experience and see it as a positive aspect of their lives.

However, some people with synesthesia may feel different from others or misunderstood by those who aren’t familiar with the condition. In this case, speaking with a therapist could be beneficial.

How can online therapy help those who live with synesthesia? 

Online therapy can be a helpful resource for those living with synesthesia who are seeking support. A therapist can create a plan that offers supportive strategies for your specific needs. For example, if you’re feeling overwhelmed or isolated, a therapist may provide coping strategies and guidance on how to improve your emotional well-being. With online therapy, you can reach out to a counselor anywhere that you’re comfortable with, as long as you have a reliable internet connection. For some, online therapy may be more affordable than traditional therapy.

Is online therapy effective for those experiencing synesthesia? 

Synesthesia does not require treatment. However, therapy can be beneficial for people living with synesthesia who are seeking emotional support. Research shows that 75 percent of people who have done psychotherapy report some kind of benefit. This can offer promise to some, especially those who are looking for new coping mechanisms and supportive strategies to navigate synesthesia with. Your therapist can create a plan that speaks to your specific needs.

Support for synesthesia

Are you or someone you know experiencing any difficulties navigating life with synesthesia? 

With BetterHelp, you can talk to a licensed professional without having to leave home or set an appointment. Get started by answering a few simple questions and you can be talking to a therapist in no time.


There are many types of synesthesia, and in most cases, no two individuals experience it in the same way. For example, some may experience auditory tactile synesthesia through which they feel sounds — and others may experience spatial sequence synesthesia in which they see numbers spatially. Synesthesia is typically not threatening and many find it to be a positive in their lives, but if synesthesia is causing difficulties in your life, online counseling may help. BetterHelp can connect you with a therapist in your specific area of need.
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