Pupil size in people with synesthesia changed depending on how bright or dark the perceived colors were.

So far, so standard. But here’s where things get interesting: if you present a visual synesthete with some input that ...

Ever caught a whiff of the color blue? Or tasted a symphony? If that sounds completely bonkers to you, you’re in the majority. But for a small slice of humanity, these cross-sensory experiences are ...

Synesthesia, the neurological condition in which one sense involuntarily triggers another, produces measurable changes in the body’s autonomic nervous system, not just unusual perceptual experiences.

Vladimir Nabokov first noticed, at age 7, his special gift of synesthesia when playing with colorful alphabet blocks that "were all the wrong color." Source: Contributor: Neil Overy/Alamy Stock Photo.

Synesthesia. It’s when someone sees colors when hearing music, the linking of sensory information with something unrelated. It’s also experienced sometimes as seeing colors in other visuals, such as ...

Daniel Tammet has memorized Pi to the 22,514th digit. He speaks ten different languages, including one of his own invention, and he can multiply enormous sums in his head within a matter of seconds.