Imagine if listening to your favorite song caused you to envision a spectrum of colors, each having a designated note, or if seeing the shape of a rectangular object caused the presence of a sour taste within your mouth. This is the everyday experience of an individual with synesthesia -- a neurological condition that is characterized as having a second sensory experience that is automatically triggered upon the use of a different sense. Synesthesia is more common than some would expect, with about one in every two thousand people having the condition. Although the exact genetic causation of synesthesia still remains unknown, researchers have advanced in their findings regarding the unique brain functioning of synesthetes. The first documented case of synesthesia dated back to 1812. Georg Sachs, a graduate student who wrote his doctorate thesis on his experience with having albinism, included a subsection of his account to his unique synesthetic perceptions. Within his descriptions, Sachs noted associating different colors with each day of the week. He explained the color associations that he saw as being in “dark space”, and as being caused not only by different words, but also by notes within music. He stated that the colors that he saw were determined by the instrument that was being played, as well as by the tone of the notes within a song. 

Although Sachs’ thesis was published in the early 1800s, researchers hadn’t begun making significant progress in their analysis of the reasoning behind the presence of this condition until almost two decades later. In the late 1980s, researcher Baron Cohen performed a longitudinal study on synesthetes over the span of a year. After asking the subjects to state the different colors that they associated with various words that were stated, he concluded that there was a strong consistency within the word-color associations that synesthetes had. This consistency is largely seen as beneficial to those with synesthesia, as it strengthens their memory through having what can be seen as an automatic mnemonic device. Another study, also led by Cohen, used fMRIs to examine possible differences within the synesthetic brain. He found that synesthetes have a comparatively higher activity level within the sensory region of their brain that is associated with the activation of their synesthesia. In his experiment specifically, it was noted that synesthetes who had color-associated hearing had a higher activity level within their auditory cortex. 

Even with the progress that has been made within synesthetic research, the current resources present to clarify the intricate inner workings of the human brain have limited their discoveries. Scientists have made multiple speculations regarding the causation behind the condition. One hypothesis is that synesthesia is the result of having additional connections within the sensory nerves of an individual’s brain. This, therefore, would lead to an intertwined perception of the world that integrates the experience of the five senses in a way that the majority of the population is unfamiliar with. Conversely, other scientists believe that synesthesia isn’t caused by extra neural connections, but instead, by the way in which a synesthete’s brain processes sensory information. Within the average brain, the information received from its surroundings is initially stored within a common area, and later is sent to the respective parts of the brain that process the individual senses. It is proposed that the transferral of this neural data is somehow interrupted, which then causes its transmission to an alternate location. 

Although the root of synesthesia remains debated, scientists have come to a consensus about the fact that, although the experience of synesthesia may have slight similarities with that of hallucinogenic disorders, synesthesia is not considered to be a pathological condition. It is rarely the cause of mental detriments to the individual that has the conditions, and, contrarily, synesthesia is known to have its benefits. As aforementioned, the condition is known to foster enhanced memory. Synesthesia is also known to increase creativity, with the likes of Vincent Van Goh, Billy Joel and Pharell Williams being a few of several famous synesthetes. The sensory connections that synesthetes experience gives them a unique ability to see the world from an intertwined lens; what most can only imagine in a metaphorical sense is a part of their reality.

References:

Carpenter, Siri. “Everyday Fantasia: The World of Synesthesia.” Monitor on Psychology, American Psychological Association, 21 Mar. 2003, www.apa.org/monitor/mar01/synesthesia.

Jewanski, Jorg, et al. “(PDF) A Colorful Albino: The First Documented Case of Synaesthesia, by Georg Tobias Ludwig Sachs in 1812.” A Colorful Albino: The First Documented Case of Synaesthesia by Georg Tobias Ludwig Sachs in 1812, Journal of the History of He Neurosciences, 2009, www.researchgate.net/publication/41563417_A_Colorful_Albino_The_First_Documented_Case_of_Synaesthesia_by_Georg_Tobias_Ludwig_Sachs_in_1812.

Ward, Jamie. “Synesthesia.” Annual Reviews, Annual Review of Psychology, June 2012, www.annualreviews.org/doi/full/10.1146/annurev-psych-113011-143840#_i34.