Synesthesia Explained: Grapheme-Color Connections and Blended Senses

Short summary

Be Smart explains synesthesia, a condition in which senses blend so that letters might evoke colors or words trigger tastes. The host recounts a 2013 experiment in which participants across the alphabet assigned colors to letters without communicating, revealing striking agreements that earned the phrase synesthesia. The video then describes grapheme-color synesthesia as the most common form and surveys more than 150 known types that mix senses in diverse ways. It explains a developmental story where exuberant synaptogenesis creates many neural connections in infancy, followed by synaptic pruning that leaves cross-linkages intact for some people. The piece also discusses how researchers verify synesthetic experiences, the inheritance pattern, and the surprising cognitive benefits reported in studies.

Introduction

Be Smart introduces synesthesia as a window into how reality can be perceived in blended ways. The video begins with a thought experiment: what color is the letter A? In a 2013 study, people were asked to assign colors to letters; the participants across many individuals agreed that A and S were red, U yellow, and W blue, with odds of such a pattern by chance far below random chance. The researchers conclude that synesthesia is a genuine, involuntary blending of senses that some people experience throughout life. Notable examples span famous scientists and artists, including Nikola Tesla, Richard Feynman, Olivia Rodrigo, Billie Eilish, and Beyonce.

What is synesthesia

The video defines synesthesia as a condition in which the perception in one sense reliably triggers a second sense. Grapheme-color synesthesia is identified as the most common form, where letters or numbers elicit specific colors. Beyond this, scientists have cataloged more than 150 different cross-sensory experiences, ranging from sounds evoking physical sensations to colors triggered by music. Some synesthetes report multiple, overlapping associations that can change over time, illustrating the rich diversity of this phenomenon.

How the brain might produce synesthesia

The explanation hinges on how brains wire together during development. At birth, exuberant synaptogenesis creates an overabundance of connections, making the infant brain hyperconnected and cross-wired in unusual ways. Over time, synaptic pruning eliminates underused connections, improving efficiency. In someone with synesthesia, pruning may leave some cross-sensory links intact, so that activating one sensory region simultaneously activates a connected sensory area. For example, hearing music might trigger smells for someone with auditory-olfactory synesthesia, or seeing a letter could evoke a color.

Prevalence, inheritance, and varieties

Approximately 1 in 25 people show some form of synesthesia, and about 40% have a close family member with the condition, suggesting a genetic predisposition. The transcript highlights that while anyone could be born with the potential for synesthesia, it does not always develop in all individuals. The video also explains the difference between synesthesia and simple memory or learned associations, emphasizing the involuntary, concurrent, and consistent nature of genuine synesthetic experiences.

Testing and consistency

To qualify as synesthesia, experiences must occur without delay, be involuntary, and stay consistent over time. The video contrasts true synesthesia with normal cross-modal associations that can be memory-based or context-driven, such as recalling fridge-magnet colors. Keeping these criteria helps researchers distinguish genuine synesthetic experiences from more common cognitive associations.

Beyond letters: types and benefits

In addition to grapheme-color synesthesia, the video surveys multiple other forms. Some people see sounds as colors, feel physical sensations from sounds, or experience synesthetic tones that overlap with space or emotion. The discussion also covers potential cognitive benefits associated with synesthesia. Studies suggest ticker-tape synesthesia (seeing words as they are heard) can aid short-term memory and information retention, while synesthetes may excel in visual tasks and spatial awareness. The video notes that such cross-sensory experiences have historically appeared in artists and scientists, suggesting a link to creativity and perceptual skills.

Can adults learn synesthesia?

Attempts to teach synesthetic letter-color pairings in adults have shown the learned associations can arise but tend to fade within weeks, implying that the naturally occurring wiring in early development is difficult to reproduce with training alone. The video emphasizes that re-wiring the adult brain to produce true synesthesia remains an open challenge, though it offers a glimpse into how synesthesia can broaden our understanding of perception and brain plasticity.

Sound symbolism and broader implications

The video also touches on sound symbolism, a cross-cultural tendency to associate certain sounds with specific shapes or emotions, which is not technically synesthesia but can illustrate how the brain maps sensory cues to meanings. Studying synesthesia helps scientists explore how networks form and prune across life, informing approaches to autism and other sensory processing differences. The takeaway is that there is more than one way to sense the world, and curiosity about these differences can enrich our understanding of human perception.

Conclusion

The piece concludes with thanks to supporters and a closing reminder of the value of diverse sensory experiences in advancing science and curiosity across audiences.