Synesthesia: When Senses Collide
- Science Holic
- 9 hours ago
- 3 min read
Author: Bryan Lin
Editors: Miriam Heikal, Linzi Yeung
Artist: Becky Li
In approximately 4% of the population, the brain's sensory wiring operates differently, creating a world where sounds have colors and words somehow have flavor. This is a neurological phenomenon, known as synesthesia, and it comes in many different forms. Synesthesia occurs when signals between sensory regions of the brain cross in unusual ways. What exactly is synesthesia? What causes this cross-wiring? What are the various forms it can take, and does it have any health implications?
To understand synesthesia, it is essential to examine how the senses function normally. Normally, sensory experiences follow a clear and direct pathway. Your sensory organs, like your eyes, for example, first pick up the information (light and shape in this case), convert that information into neural signals, and transmit the signals to specialized brain regions (V4 area, parietal cortex, or auditory cortex, depending on what type of input) for interpretation. In synesthetes, this pathway operates differently. Instead of the sensory experience traveling to a single designated processing area, the information activates multiple processing areas at once. This creates the dual experiences that the synesthetes experience, such as being able to hear and taste a song simultaneously. These secondary experiences occur automatically and consistently, and can be turned off. This does not mean you are stuck with synesthesia forever, however, as it can sometimes weaken or completely wear off as you age.
Although the phenomenon of synesthesia remains a relatively mysterious topic, researchers have identified several key factors contributing to it. The prevailing idea is that synesthetes have an abundance of neural connections between their distinct sensory processing regions, which would usually remain separated. During early childhood, all brains have excess neural pathways, but they are generally eliminated through a natural pruning process as you age. This, however, is not the case in synesthetes. Additionally, there is also evidence that points to genetics, as synesthesia tends to be present among multiple family members of synesthetes.
This condition can also manifest in multiple forms, the most common being grapheme-color synesthesia, where letters and numbers can trigger specific color associations. Another common type of Synesthesia is called comesthesia, where auditory input (such as music) causes a visual color experience. Mirror touch synesthesia is particularly interesting, as the condition causes individuals with it to experience physical sensations that correspond to what they’re observing. A person with mirror touch synesthesia may feel as though they are being touched when they watch someone else touch their own face. Because human senses can detect countless different qualities, like pitch and volume in sound, temperature and texture in touch, or hues and patterns in vision, and because these sensory experiences can combine with abstract concepts like time, language, and numerical sequences, researchers have catalogued at least 60 distinct varieties of synesthesia, with some estimates reaching beyond 150 forms.
Despite the unusual nature of these experiences, Synesthesia is not directly linked to any negative health problems or physical disorders. People are typically born with the condition or develop it early in childhood, and synesthesia remains a stable characteristic that follows them throughout life, with a small potential for it to weaken or disappear as they age. Some evidence also suggests that synesthetes may be more likely to possess higher intelligence levels, but it is hard to say if that is indicative of synesthetes as a whole.
Synesthesia is a fascinating neurological phenomenon that reveals that human perception is far more varied than previously typically assumed.
Citations:
The Synesthesia Tree. (2021, April). List of synesthesia types by prevalence.
Cleveland Clinic. (2023, May 3). Synesthesia. https://my.clevelandclinic.org/health/symptoms/24995-
Ask the Doctors. (2022, November 30). People with synesthesia experience the world with multiple
senses. UCLA Health. https://www.uclahealth.org/news/article/people-with-synesthesia-
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