Synesthesia - When Senses Mix

Audience: Middle and High School Students

‘“And I see colors when I hear your voice,” - “Synesthesia,” a song by Andrew Mcmahon. Image by Getty Images, from Unsplash. 

Do you see certain colors in your mind when you listen to music? Or perhaps smell a specific scent and then immediately see certain shapes? If you do, you are a part of the roughly 3 to 5% of the global population  who experience this unique type of perceptual phenomenon, known as synesthesia. But what exactly is synesthesia, and why does it happen to certain people?

To understand what this phenomenon is, it is important to explore its neurological basis. Synesthesia occurs when the stimulation of one sensory pathway leads to involuntary experiences in a second sensory pathway. It blends and amplifies senses, creating involuntary connections between colors, sounds, tastes, and textures. One of the first recorded cases of an individual experiencing synesthesia was in 1812, when Austrian physician Georg Tobias Sachs wrote a dissertation, noting, “In the alphabet, A and E are vermilion, A however is more cinnabar, E is more inclined to rose…” Since then, synesthesia has become quite widespread, and has become more popular among the social consciousness.

Types of Synesthesia and Its Possible Genetic Basis

Our perception and interpretation of external stimuli varies greatly from person to person. The way we perceive things changes so much based on our expectations as well as our knowledge, memory, and emotions, so it isn’t surprising that the same is true with this psychological phenomenon. Some people experience subtle crossovers, while others perceive vivid, overwhelming associations. These sensations can be constant or situational, shaping perception in ways that are both enriching and disorienting.

Here are some types of synesthesia from most to least common:

• Grapheme-color synesthesia occurs when letters and numbers are associated with specific colors.

• Chromesthesia occurs when certain sounds (like voices) can trigger someone to see colors.

• Auditory-tactile synesthesia occurs when a sound prompts a specific bodily sensation (such as tingling on the back of one’s neck).

• Lexical-gustatory synesthesia occurs when hearing certain words triggers distinct tastes. (like tasting chocolate when hearing the word “Monday.”)

So, is a person more likely to have a certain form of synesthesia if a parent or relative has it?     Well, it depends.

While there is no specific “synesthesia gene,” research has shown that 40% of synesthetes have a close relative who also experiences synesthesia, suggesting a genetic link. As such, many scientists believe that this is a polygenic condition, where multiple genes influence how the brain processes sensory information. Interestingly, not everyone who inherits genetic traits for this condition shows signs of synesthesia. In some instances, synesthesia may be a dominant trait with incomplete penetrance, meaning that someone can carry the trait without fully expressing it. Environmental factors, such as how the brain develops in early childhood, may also play a role. It is possible that synesthetic tendencies can be latent, only becoming active under certain conditions, like brain plasticity during early development.

Can Synesthesia Have Varying Levels of Intensity, and Can It Be Learned?

Some researchers believe that mild forms of cross-sensory associations exist in many people. For example, the bouba-kiki effect shows that even non-synesthetes often match sounds like "bouba" with round shapes and "kiki" with sharp, jagged ones. This supports research that synesthesia may indeed exist on a spectrum. 

There is some research out there suggesting that synesthesia-like experiences can be induced. For example, with intensive training or with certain psychedelic substances, people can start associating colors with numbers or sounds over time. However, whether learned or as a result of a substance, these types of connections don't normally create long-term synesthesia. 

Additionally, one fascinating theory is that all infants may start out with a kind of “general synesthesia” early in life. This is due to the fact that the brain has extra connections between sensory regions when we are first born, which may allow babies to experience the world in a more “blended” way. As the brain matures, sensory areas sharpen, becoming more specialized and distinct. The number of early neural pathways that remain intact would then reflect to what degree an individual’s synesthesia stays connected into adulthood. 

Links Between Synesthesia, Creativity, and Memory

Although synesthesia is typically present from childhood, many synesthetes grow up unaware that their sensory world is unique. Take Pharrell Williams, the globally known musician, producer, and entrepreneur, who has openly discussed his experience with chromesthesia, in which sounds involuntarily evoke colors. As a child, Pharrell thought his colorful perception of music was just part of how everyone heard sound. He later came to recognize that these vivid color associations were actually a form of synesthesia, which has since shaped much of his musical creativity. He claims, "It’s like a cloud of colors and shapes when I hear sounds. Music gives me a visual experience before it becomes an auditory one."

Pharell’s life and career is a testament to how synesthesia is also strongly linked to creativity. Studies have shown that synesthetes are more likely to work in creative fields such as music, art, literature, and design. Many famous figures, including Billie Eilish, and Charlie XCX have opened up about their condition, delving into how it serves as inspiration for creating innovative art, music, or writing. In addition to this, many Tiktokers have spread awareness of life with synesthesia. Millions of people have viewed colorful artistic displays these influencers created for music that they listen to, getting a glimpse into what a song looks like inside their minds.

Along with this, one of the most well-known advantages reported by synesthetes is enhanced memory recall. For example, someone with grapheme-color synesthesia might remember phone numbers or dates more easily because each digit has a specific color, helping the brain to store and retrieve information faster and more vividly. 

Because these perceptions often bring joy or fascination, many synesthetes seek ways to amplify them. Some try mindfulness techniques or experiment with creating art, music, or poetry based directly on their unique sensory blends. Others simply value synesthesia as a calming influence or a personal "secret world" that makes everyday life richer.

Synesthesia is more than a curious quirk of the brain. It’s a gateway to understanding how our senses, memory, creativity, and emotions are deeply connected. As scientists continue to explore synesthesia, future research holds the promise of unlocking new psychological insights. Could the neural pathways that cause synesthesia be activated in more people? Could understanding synesthesia help design new ways to teach, boost memory, or treat sensory processing disorders? These are just a few of the questions that researchers are working to answer.

Ultimately, studying synesthesia deepens our appreciation for cognitive diversity and offers exciting possibilities for education, psychology, and neuroscience. As we learn more about this extraordinary condition, we might also learn more about the untapped potential inside every brain, including our own.

Bibliography

Psychology Today Staff. (n.d.). Synesthesia. Psychology Today, https://www.psychologytoday.com/us/basics/synesthesia

Roth, I. (2023, February 1). Is synesthesia learned? Psychology Today, https://www.psychologytoday.com/us/blog/illusions-delusions-and-reality/202302/is-synesthesia-learned

Rouw, R., & Scholte, H. S. (2007). Increased structural connectivity in grapheme-color synesthesia. NeuroImage, 39(3), 1083–1089. https://doi.org/10.1016/j.neuroimage.2007.09.061

Spillmann, L. (2020, August 1). Early studies in synesthesia. World Neurology, https://www.worldneurologyonline.com/article/early-studies-in-synesthesia/