The Tell-Tale Brain: A Neuroscientist's Quest for What Makes Us Human

Francis Galton, a cousin of Charles Darwin and one of the most colorful and eccentric scientists of the Victorian era, conducted the first systematic study of synesthesia in the 1890s. Galton made many valuable contributions to psychology, especially the measurement of intelligence. Unfortunately, he was also an extreme racist; he helped usher in the pseudoscience of eugenics, whose goal was to “improve” mankind by selective breeding of the kind practiced with domesticated livestock. Galton was convinced that the poor were poor because of inferior genes, and that they must be forbidden from breeding too much, lest they overwhelm and contaminate the gene pool of the landed gentry and rich folk like him. It isn’t clear why an otherwise intelligent man should hold such views, but my hunch is that he had an unconscious need to attribute his own fame and success to innate genius rather than acknowledging the role of opportunity and circumstance. (Ironically, he himself was childless.)

Galton’s ideas about eugenics seem almost comical in hindsight, yet there is no denying his genius. In 1892 Galton published a short article on synesthesia in the journal Nature. This was one of his lesser-known papers, but about a century later it piqued my interest. Although Galton wasn’t the first to notice the phenomenon, he was the first to document it systematically and encourage people to explore it further. His paper focused on the two most common types of synesthesia: the kind in which sounds evoke colors (auditory-visual synesthesia) and the kind in which printed numbers always seem tinged with inherent color (grapheme-color synesthesia). He pointed out that even though a specific number always produces the same color for any given synesthete, the number-color associations are different for different synesthetes. In other words, it’s not as though all synesthetes see a 5 as red or a 6 as green. To Mary, 5 always looks blue, 6 is magenta, and 7 is chartreuse. To Susan, 5 is vermillion, 6 is light green, and 4 is yellow.

How to explain these people’s experiences? Are they crazy? Do they simply have vivid associations from childhood memories? Are they just speaking poetically? When scientists encounter anomalous oddities such as synesthetes, their initial reaction is usually to brush them under the carpet and ignore them. This attitude—which many of my colleagues are very vulnerable to—is not as silly as it seems. Because a majority of anomalies—spoon bending, alien abduction, Elvis sightings—turn out to be false alarms, it’s not a bad idea for a scientist to play it safe and ignore them. Whole careers, even lifetimes, have been wasted on the pursuit of oddities, such as polywater (a hypothetical form of water based on crackpot science), telepathy, or cold fusion. So I wasn’t surprised that even though we had known about synesthesia for over a century, it has generally been sidelined as a curiosity because it didn’t make “sense.”

Even now, the phenomenon is often dismissed as bogus. When I bring it up in casual conversation, I often hear it shot down on the spot. I’ve heard, “So you study acid junkies?” and “Whoa! Cuckoo!” and a dozen other dismissals. Unfortunately even physicians are not immune—and ignorance in a physician can be quite hazardous to people’s health. I know of at least one case in which a synesthete was misdiagnosed as having schizophrenia and was prescribed antipsychotic medication to rid her of hallucinations. Fortunately her parents took it upon themselves to get informed, and in the course of their reading came across an article on synesthesia. They drew this to the doctor’s attention, and their daughter was quickly taken off the drugs.

Synesthesia as a real phenomenon did have a few supporters, including the neurologist Dr. Richard Cytowic, who wrote two books about it: Synesthesia: A Union of the Senses (1989) and The Man Who Tasted Shapes (1993/2003). Cytowic was a pioneer, but he was a prophet preaching in the wilderness and was largely ignored by the establishment. It didn’t help matters that the theories he put forward to explain synesthesia were a bit vague. He suggested that the phenomenon was a kind of evolutionary throwback to a more primitive brain state in which the senses hadn’t quite separated and were being mingled in the emotional core of the brain.

This idea of an undifferentiated primitive brain didn’t make sense to me. If the synesthete’s brain was reverting to an earlier state, then how would you explain the distinctive and specific nature of the synesthete’s experiences? Why, for example, does Esmeralda “see” C-sharp as being invariably blue? If Cytowic was correct, you would expect the senses to just blend into each other to create a blurry mess.