The World of Synesthesia

Tasting words, seeing voices, and feeling sounds is normal for people with synesthesia. This cognitive trait occurs when a stimulus activates two or more senses. For example, a synesthete might hear the national anthem and taste strawberry pie. The same song could trigger an ear tug or orange spirals in someone else. Or—in rare cases—a synesthete might experience a mixture of all five different senses!

What is synesthesia?

An unconscious, automatic, consistent cross-activation of different senses, synesthesia is a neurological condition with an unknown cause that affects about 4 percent of the population (307 million people worldwide).

Not all tastes, smells, sounds, and visuals are pleasant. Some synesthetes report unsavory or even painful sensations, such as in the BBC documentary Derek Tastes of Earwax.

Many synesthetes don’t realize how unusual they are. They don’t talk about seeing the days of the week as blocks or tasting chocolate when they hear music. Some assume everyone knows numbers have personalities (joyful sevens; paranoid nines); others tried to describe their perceptions but received a negative response.

Synesthesia research holds promise for cognitive health

Patricia Lynne Duffy, a synesthete and research study participant, assumed everyone saw different-colored letters. Then, when her dad was teaching her to write, she realized that “to make an ‘R,’ I just had to draw a ‘P’ and add an extra line. I was so surprised I could turn a yellow letter into an orange letter just by adding a line.”

Duffy—author of Blue Cats and Chartreuse Kittens: How Synesthetes Color Their Worlds (WH Freeman, 2001)—says scientists are applying their growing understanding of synesthesia in therapeutic ways.

“An MIT [Massachusetts Institute of Technology] researcher is developing cross-sensory stimulation tools that look promising for treating Alzheimer’s disease,” Duffy says. “It’s been discovered that cross-sensory stimulation is vital for helping the brain clean up its excess ‘plaques and tangles’ that can cause cognitive decline.”

How is synesthesia determined?

Early scientists speculated that babies are born with a mass of structural synapses; as babies grew, and with lived experiences, excess synaptic connections would be discarded. They surmised that synesthetic brains hadn’t been sufficiently “pruned,” leaving them with “increased wiring.”

Since the early 1990s, neuroscientists have verified synesthesia with a robust battery of tests developed by psychologist Simon Baron-Cohen. To validate synesthesia, these tests were applied over extended time intervals to test for consistency of sensations. When participants associate specific stimuli (for example, a word or shape) with the exact same sensory perceptions over time, they are developmental synesthetes.

Cognitive scientists are now using brain scans to better understand synesthesia. “In fMRI … regions close to color areas in the visual cortex light up in response to reading black and white numbers for synesthetes,” Dr. Julia Simner, editor of The Oxford Handbook of Synesthesia (Oxford University Press, 2013), told the American Psychological Association, while “for controls, those same regions would only light up if they were exposed to color in the real world.”

Further, Dutch scientists are now discovering different structural or physical qualities in synesthetic brains.

Some scientists believe the extra cross-sensory processing gives synesthetes “extra perceptual hooks” that lead to superior memories and cognitive abilities. Research also suggests higher rates of autism in synesthetes, suggesting the two conditions may share underlying mechanisms.

How can we “practice” synesthesia?

Mental exercises that stimulate your brain can help reduce anxiety and depression, improve cognition, and increase quality of life. Activating your brain in fresh ways can generate new neurons. This stimulation helps you stay sharp and decreases the risk of some cognitive diseases.

Practicing synesthesia isn’t just a brain exercise but a powerful way to experience the present moment. You’re more engaged in the physical environment and more attuned to your bodily sensations and intuition. You may even be less distracted by anxieties and other painful thoughts.

“Synesthesia is actually a normal brain function in every one of us, but its workings reach consciousness in only a handful,” writes Dr. Richard Cytowic, author of <The Man Who Tasted Shapes> (Bradford Books, 2003).

In one study, blindfolded volunteers “saw” a touch, sound, or word even though their eyes were covered. Their primary visual cortex responded despite having no external stimuli, which meant their brain changed to adapt to the environment. Other exercises, such as reading in color, have also been found to activate synesthetic traits.

Try associating things you normally wouldn’t, such as “hearing” fragrances or “tasting” voices. If you meditate—a practice that enhances perceptual sensitivity— allow unexpected sensations to arise. Experienced meditators report seeing visual images, colors, and light during deep meditation.

“Each of us—synesthetic or not—experiences the world in a way nobody else does,” says Duffy. “Our brain pattern for processing information is as unique as a fingerprint. It’s great to become more aware of how we see the world in our own unique way.”