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.
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.
2.) 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:

3.) 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; 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.
• 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.
• Visualized sensations.

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