Imagine choosing a career in psychology. Because you’re particularly driven, after graduating from high school you enroll at a university where you immediately declare your major. For the next four years you spend every waking hour reading, talking and thinking about the human mind. You learn how to diagnose both the most common and most rare of mental conditions. Upon graduation you move across the country to pursue your PhD, spending five more years learning the mechanisms behind perception and action. You’ve been so productive during your post-graduate years that you’re whisked away by a tenure track position where you have great influence over younger versions of yourself for many years. 

Except one day everything you thought you knew about the mind is brought into question after you make a simple remark about musical abilities. “It’s just like how each note has a specific color,” you tell your students. But those students haven’t a clue what you’re talking about. “What colors?” they ask. It’s at that moment you realize you’re not like everyone else. So you do some research to see if there are others like you. You discover you are a synesthete, the proud holder of a condition where the senses are mixed. You’re much like Mary, a psychologist who phoned in to my recent NPR spot.

Synesthesia is a condition where input in one sensory stream gives rise to experiences in another unstimulated sensory stream. One of the most common forms is grapheme-color synesthesia, where looking at or thinking about letters or numbers written in black elicits the experience of color. Some grapheme-color synesthetes see colored letters floating out in the world among the black characters that induce the experience. These synesthetes are called projectors. Other synesthetes don’t actually see anything, but have a strong feeling that colors, textures or personalities are connected with particular graphemes.

But not all synesthesia involves visual experiences. Lexical-gustatory synesthetes experience taste sensations when they hear or think about words. Music-touch synesthetes claim to actually feel music. Such is the case with one of my lab’s case studies, Megan. She feels the sounds of a piano literally “poking” her face. String instruments vibrate in her chest. Waves from brass instruments pass in front of her, sometimes buzzing on her neck. Drums come up from below. Intensity increases with volume but these sensations are never unpleasant, as Megan feels like she is in the music. Other forms of synesthesia are more unique. For example, another one of our case studies, Jason, experiences visual imagery associated with complex mathematical formulas.

Most forms of synesthesia are developmental, but the condition can also be acquired. Yet another one of our case studies, Derek Amato, started seeing little black and white squares that constantly flow across his field of vision after suffering a severe concussion. Three days later he sat down and started playing the piano like a pro despite having no musical training whatsoever. He explained that he merely follows the black and white blocks. They tell him where his fingers should go.

We currently don’t know how this fascinating condition develops, but there are a few hypotheses. One hypothesis is that cross-activation of adjacent brain regions gives rise to multimodal experiences. For example, in the case of grapheme-color synesthesia, activation of adjacent word-form and color areas results in color being bound into conscious experience. Another hypothesis holds that unusual crosstalk is a result of disinhibited feedback from one area of the brain that binds information from different senses. A third theory holds that complex information re-enters the regions of the brain that generates visual imagery. My lab has recently proposed a fourth hypothesis related to memory.  Our theory is that strong associations among certain types of sensory input and objects stored in long-term memory become conscious in the form of synesthetic colors, feelings or sounds.

If you think you have synesthesia, I encourage you to take the Synesthesia Battery, an automated diagnostic test that covers the most common forms of the condition. You can also learn more about current research on the condition at my lab’s website.

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