The post Only About 4% of People Have Synesthesia — 7 Fascinating Things Researchers Have Found first appeared on Crafting Your Home.
Imagine hearing a piece of music and seeing colors, reading the number 7 and automatically experiencing it as blue, or tasting something when you hear a particular word. For most people, these descriptions sound metaphorical. For people with synesthesia, they describe consistent, involuntary aspects of perception.
Synesthesia is a fascinating example of how differently the human brain can process the same information. Researchers have studied it for decades, using behavioral experiments, psychological testing, and brain-imaging techniques to understand how one stimulus can trigger an additional sensory experience.
One widely cited population study published in Perception in 2006 estimated that about 4.4% of the population had one of the forms of synesthesia tested. That is roughly 1 in 23 people. Importantly, researchers should not treat this as a universal percentage for every type of synesthesia: prevalence depends on which forms researchers test and how they define synesthesia.
Here are seven of the most interesting things researchers have discovered.
Some People Really Do Experience Letters and Numbers as Colors
One of the best-known forms is grapheme-color synesthesia. In this form, seeing a letter or number can automatically trigger a particular color. A person might consistently experience the letter A as red or the number 5 as green. The important word is automatically. This is not simply someone deciding that a particular letter “feels” like a certain color. Researchers have developed behavioral tests in which people repeatedly assign colors to letters or numbers. People reporting grapheme-color synesthesia tend to produce much more consistent pairings than control participants asked to make similar associations.
That consistency has made synesthesia unusually useful to scientists. Instead of relying only on a person’s description of an internal experience, researchers can measure whether the reported associations remain stable across repeated tests.
Evidence also suggests these associations are not completely random. Studies have found that language, familiarity with letters, and other learned factors can influence the colors people experience. Research on grapheme-color synesthesia therefore suggests that both unusual perceptual experiences and ordinary learning processes can contribute to the final association.
Related: Exploring Superstitions: The 10 Mystical Beliefs Surrounding Numbers
Music Can Become a Visual Experience
Synesthesia is not limited to letters and numbers. In sound-color synesthesia, also known as chromesthesia, sounds can trigger visual experiences such as colors or shapes. The experience can vary widely from person to person. One person may associate a particular musical note with blue, while another may experience the same note differently. Some people report more complex visual experiences involving combinations of colors, movement, or patterns.
Researchers describe synesthesia in terms of an inducer and a concurrent. The inducer is the stimulus that triggers the experience, while the concurrent is the additional sensation. In auditory synesthesia, for example, a sound can act as the inducer while a color becomes the concurrent. Other combinations are even more unusual. Researchers have documented lexical-gustatory synesthesia, in which words or speech sounds can trigger taste experiences. A 2003 study published in Cognition described a case in which particular speech sounds produced involuntary taste sensations and found that linguistic and conceptual information influenced the associations.
In other words, “mixed senses” is a useful starting description, but synesthesia is much more varied than simply seeing colors when you hear music.
Synesthetic Associations Can Be Extremely Consistent — But They Are Not Always Fixed
Consistency is one characteristic researchers have used to distinguish synesthesia from ordinary associations. If someone without synesthesia is asked what color the letter B should be, their answer can change depending on context, mood, or personal preference. A person with grapheme-color synesthesia may repeatedly give the same color for B across testing sessions.
That does not mean every synesthetic association is permanently frozen. More recent research has shown that individual grapheme-color associations can change, particularly over longer periods. A longitudinal study published in Consciousness and Cognition found that some color pairings changed over adulthood, demonstrating that consistency is better understood as a characteristic tendency than an absolute rule.
This distinction matters because early descriptions sometimes treated synesthesia as completely fixed. Current research presents a more nuanced picture: synesthetic associations can be highly consistent while still being influenced by learning, familiarity, and other factors.
Synesthesia May Be Linked to Better Memory
One intriguing finding concerns memory. Several studies have reported that people with synesthesia can show enhanced memory performance. A 2019 meta-analysis published in Memory examined this literature and found that synesthetes showed a medium-sized advantage in long-term episodic memory compared with controls. The effect for working memory was smaller but still statistically above that of controls.
At first, the explanation seems obvious. If a letter automatically comes with a particular color, that additional information might provide another way to remember it. But the research is more complicated. The same meta-analysis found that the memory advantage was not limited to material that directly triggered a person’s synesthetic associations. For example, some improvements appeared for information that had no obvious connection to the person’s synesthesia. That makes it difficult to explain the entire effect simply as an extra color or sensory “label.”
A review published in Neuroscience & Biobehavioral Reviews similarly concluded that enhanced memory in synesthesia cannot be explained entirely by richer encoding of synesthesia-inducing material. The relationship involves broader differences at the boundary between perception and memory. For technology enthusiasts, the finding is particularly interesting because it raises a broader question: could unusual sensory integration reveal new principles about how humans store and retrieve information?
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The Brain Does Not Appear to Rely on One “Synesthesia Center”
It is tempting to imagine that scientists have discovered a single part of the brain responsible for synesthesia. The evidence does not support such a simple explanation. Brain-imaging research has reported differences involving sensory regions as well as areas associated with attention, integration, and higher-level processing. A review of MRI research concluded that synesthetic experiences appear to involve a network of brain regions, rather than one isolated location.
Researchers have proposed several explanations for this unusual cross-sensory processing. One influential idea involves stronger or differently organized connections between systems that normally process different kinds of information. Other models emphasize how sensory information is integrated with learned associations and higher-level processing. However, caution is warranted. A critical review of the neuroimaging literature published in Frontiers in Human Neuroscience found substantial methodological problems in some earlier studies, including small sample sizes and statistical limitations. The authors argued that the precise neural signature of synesthesia had not been firmly established.
So the strongest conclusion is not that scientists have found a definitive “synesthesia circuit.” Rather, research suggests that synesthetic experiences involve interactions across multiple perceptual and cognitive systems, while the exact neural mechanisms remain an active research question.
Synesthesia Can Run in Families
Evidence also suggests genetics plays a role. Researchers have observed familial patterns of synesthesia for many years. In one study of 53 people with synesthesia, 42% reported having a first-degree relative with synesthesia. When researchers investigated families directly, they found that different types of synesthesia could occur within the same family. That does not mean there is a single “synesthesia gene.” The evidence is considerably more complicated.
People in the same family can have different forms of synesthesia, and the specific associations can vary from one person to another. This suggests that inherited factors may contribute to a person’s likelihood of developing synesthesia, while other biological and developmental factors influence how that synesthesia ultimately appears.
A useful way to think about the current evidence is that genes may influence the developmental conditions under which synesthesia can emerge, rather than simply determining a fixed sensory map.
Synesthesia Is Not Simply a “Superpower”
Popular articles sometimes describe synesthesia as a cognitive superpower. The scientific evidence is more complicated. Some studies have found advantages in particular areas, including memory, imagery, or visual-spatial processing. But these findings do not mean that every person with synesthesia has superior cognitive abilities. A study of 82 people with different forms of synesthesia found greater involvement in creative arts and better performance on one creativity measure, but not on another. The researchers concluded that greater artistic involvement and performance on standard creativity tests should not automatically be treated as the same thing.
A later systematic comparison likewise found differences in areas such as mental imagery and some creativity-related measures, while emphasizing that synesthetes are not uniformly exceptional across every cognitive ability. Synesthesia can therefore involve unusual strengths, but it can also be distracting or demanding depending on the individual and the type of experience. The safest scientific description is that synesthesia represents a distinctive way of experiencing and processing information, not a universal upgrade to the human brain.
Could You Have Synesthesia?
People sometimes discover synesthesia only after learning that others do not experience the world the same way.
A person might assume that everyone sees letters in particular colors, experiences sequences in specific locations, or associates certain sounds with visual patterns. Discovering that these experiences are unusual can be surprising.
Researchers, however, do not diagnose synesthesia simply by asking someone whether a letter “feels” like a color. Standardized behavioral tests can examine the consistency and characteristics of reported associations, providing a more objective way to study the phenomenon.
An online quiz can therefore be an interesting introduction, but it should not be treated as a scientific diagnosis.
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