Synesthesia – The Joining of the Senses

July 9, 2021 by Anna Peris Artwork by Anna Peris

Vincent Van Gogh, writer Vladimir Nabokov, and Australian singer Lorde, a seemingly unrelated trio, share one unifying experience – all are among the small group of people with the neurological condition of synesthesia. People with this condition, called synesthetes, involuntarily experience sensory reactions, from a stimulus that activates a different sensory pathway. Since the sensory experiences and the stimulus that causes them varies widely among synesthetes, over eighty forms of synesthesia have been identified. Two of the most commonly known types are grapheme-color synesthesia and chromesthesia. Grapheme-color synesthesia causes a person to perceive particular colors when seeing letters, and chromesthesia is when sounds, whether they are musical or ambient, prompt individuals to see colors. Some synesthetes experience words as having unique flavors, while, for others, sounds will elicit physical sensations. Many possess more than one type of synesthesia (Safran et al, 2015).  

The exact physiological processes behind synesthesia have not been fully revealed, but neurological research has demonstrated that sensory experiences are related to an abundance of connections in the white matter tracts between sensory regions of the brain. When a stimulus activates one sensory region, this heightened connectivity causes the neural activity to overflow into other regions. For grapheme-color synesthesia, the adjacent regions responsible are the fusiform gyrus and V4 regions. The fusiform gyrus is a region that deals with visual appearance and recognition, and the V4 region is a part of the visual cortex that deals with color perception. FMRI studies have indicated that the white matter connectivity for grapheme-color synesthetes is heightened in the superior parietal lobule, as shown in the image below (Hubbard et al, 2005).

For those synesthetes that associate numerical sequences and other concepts like months of the year with color, it is thought that this is a result of the interaction between the angular gyrus, a part of the inferior parietal lobule associated with numeric processing, and the V4 region. This conclusion of interaction between sensory regions has been solidly supported as the basis for these two forms of synesthesia, while there is less evidence that this process is what controls some of the more rare forms of the condition. Genetic studies of synesthetes have suggested that synesthesia can be genetically inherited. However, since the studies identified numerous genes inconsistently related to inheritance of synesthesia among different families, no particular gene or gene cluster has been labelled as the singular gene responsible for synesthesia inheritance (Ramachandran and Hubbard, 2001). 

While synesthesia is by no means common, it is less rare than commonly thought, with an estimated 2 to 4 percent of the global population experiencing some form of the condition. Among artists and musicians, it is more prevalent. Many of the famous examples of synesthetes fall into this group. Since many synesthetes constantly perceive such strong visual experiences due to sounds or letters, these colours and shapes often inspire works of art both visual and musical. Besides Van Gogh, some famous artists with this condition include Wassily Kandinsky (a Russian artist), Edgar Degas (a French artist), and Edvard Munch (a Norwegian artist). The influence of chromesthesia is highly evident in the works of Kandinsky. He often wrote about how he saw colors when he heard music, and he heard music when creating his artwork. In a 1915 letter to colleague Gabriele Munter, he wrote, 

“First I will make different color tests: I will study the dark – deep blue, deep violet, deep dirty green, etc. Often I see the colors before my eyes. Sometimes I imitate with my lips the deep sounds of the trumpet – then I see various deep mixtures which the word is incapable of conceiving and which the palette can only feebly reproduce” (Boehmer, 2011). 

Kandinsky’s “Impression III,” inspired by a concert he attended

Melissa McCracken is an American contemporary artist with chromesthesia, and she creates paintings based on the colors particular songs evoke for her, as shown in a few of her works below. 

Melissa McCracken, Inspired by “Karma Police” by Radiohead

Beyond the world of visual art, many musical artists are synesthetes. Composers such as Franz Liszt, Jean Sibelius, and Nikolai Rimsy-Korsakov all experienced chromesthesia. Contemporary musicians with the condition include Jimi Hendrix, Lady Gaga, Frank Ocean, Pharrell Williams, and countless others. Some synesthetic songwriters have described what they see when hearing their own compositions. In an interview, Billy Joel mentioned that some of his more sentimental songs like “Vienna” are equated with soft shades of green and blue. For some musicians, perfect pitch overlaps with synesthesia, and scientific studies have demonstrated that these two phenomena often coincide. A 2013 study reported that out of 768 subjects with validated absolute pitch, 155 exhibited synesthesia, demonstrating a strong association between these two traits. Additionally, the study concluded that there was a significant genetic overlap between the two phenomena (Gregersen, et al., 2013). 

While the first written example of synesthesia is from Pythagoras in 500 BC, synesthesia was not formally discovered as a condition until the nineteenth century. Likely synesthetes prior to this time period, including Van Gogh, were often misunderstood as insane when relating their experiences to others. As more research was undertaken, and brain imaging validated the experiences reported by synesthetes, the condition was gradually destigmatized (Safran, 2015). Research into synesthesia continues today, as more and more hypotheses about the physiological and genetic bases of the condition are proposed. One such hypothesis that holds some popularity is that many individuals experience synesthesia to some degree, even if it is very slight, based on the observation that some people experience involuntary associations between senses in response to a few limited stimuli. Continued synesthesia research is thought to be helpful to our scientific understanding of other conditions such as autism, dyslexia, and loss of a particular sensory function. It may also contribute to research about memory and absolute pitch (Ramachandran and Brang, 2008). No matter how many discoveries about the condition are made, synesthesia still remains as a source of intrigue and an inspiration of artistic work.