To most readers, this text looks black and white. But to a few, each letter possesses a different color, and reading becomes more than what’s in black and white.   

Those who read in color live with grapheme-color synesthesia, where the brain assigns colors to letter and numbers. Some synesthetes say words possess colors, too (someone might say truth looks gold, for example). Overall, 4 percent of the population experiences a form of synesthesia with 1 percent living with grapheme-color synesthesia.

Synesthesia gives many people a richer experience and it’s believed to be mostly harmless and fixed—people either have it or they don’t.

Until now.

Researchers at the University of Amsterdam found that people, without a history of grapheme-color synesthesia, who read books with some colored letters, associated those letters with the correlating hues. This is the first time anyone has taught synesthesia by reading books. 

“Whenever we give a talk or lecture, people ask if they can learn synesthesia,” says Olympia Colizoli, a doctoral student in the brain and cognition department at the University of Amsterdam.

“Most people would never want to give up their synesthesia and can’t imagine not having these experiences.”

To test whether people could learn grapheme-color synesthesia, Colizoli asked 15 subjects to read books that had four frequently occurring letters paired with four commonly seen colors. Each participant selected a book from Project Gutenberg and Colizoli applied color to the book (prior to the experiment she colored every letter in a book but it made it very difficult to read). Colizoli’s interest isn’t simply professional; she has "time form" synesthesia, which means she sees periods of times, such as days, weeks, or centuries, as shapes.

“Even though [synesthesia] seems to run in families and the evidences suggests it is genetic, language is learned and it comes from the environment … no one is born with the letter a in their brain,” she says. Yet, there seems to be little understanding of the role of environment and synesthesia. 

Prior to reading the colored book, Colizoli asked the participants to take a modified Stroop test, which detects grapheme-color synesthesia, to assure none of the subjects had it. In a modified Stroop test, people look at the words printed in different colored ink. Grapheme-color synethetes have delayed responses when identifying the letters’ colors.

After completing the book, the subjects re-took the Stroop test and showed behavioral signs of synesthesia. Colizoli does not believe these effects are permanent, noting more research needs to be conducted. She and her colleagues also replicated the results with participants who read in Dutch.

“We are bombarded by colored letters all the time,” Colizoli says. “It is interesting to see how adaptive [synesthesia] may be.”

Colizoli also asked the subjects if they noticed any differences since the experiment and they gave a variety of subjective responses (much like synesthetes would). One person claimed to dislike orange until reading in color, while two subjects say they now read faster. Another woman, a musician, enjoyed reading in color so much she asked if Colizoli could print all her sheet music in color for her. (This is not uncommon; artists frequently claim to be synesthetes. Vladimir Nabokov saw the alphabet in rainbow colors with each letter appearing the same shade each time he saw it.)   

“She could remember the music better and fell in love with it. Some people were really sensitive to it.”  

The paper appears in the online journal PLoS ONE. If you want to try reading like a grapheme-color synsethete, check out this link.

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