On Mon., Nov. 2, Edward Hubbard, a researcher at the University of California, came to Yale’s John Pierce Laboratory to deliver a talk titled “How the Study of Synesthesia Sheds Light on Basic Cognitive and Perceptual Processes.” For those of you who couldn’t make the talk, Dr. Lawrence Marks of the School of Public Health provided The Herald with a peek at his research on the subject.

The sensation of hearing colors or tasting sounds is something that hardly anyone can relate to without the use of psychoactive drugs. Synesthesia is the arousal of a sensation in a second unstimulated sense by the stimulus of a particular sense; for example, when listening to music, a synesthesiac might see colors. Yale Professor of Psychology Dr. Lawrence Marks has been researching synesthesia for over 30 years. As a member of the Board of Directors for the American Synesthesia Association, he is one of the foremost authorities on synesthesia. He explained what the condition entails and how it is researched.

“Synesthesia is not a disease or disorder,” said Marks, “It refers to experiences that don’t have stimuli which are to be distinguished from hallucinations.” Synesthetes don’t imagine their unprovoked experiences; rather, the experiences actually happen. The condition is not restricted to seeing colors when hearing music. Other examples include experiencing tastes when a hearing music or a word. In milder cases, a subject may see the letters in the alphabet as different colors, or he or she may see a straight number line as weaving through space. Synesthetes can consistently produce their specific secondary responses. “When you look at their brains, there’s activity that looks different from people who don’t have synesthesia,” said Marks.

It is thought that about five percent of the population has synesthesia, with most of the cases being mild. There are standard long-term behavioral consistency tests used to verify if a person has the condition. The Stroop Interference Test, for example, asks a subject to read the word “red” written in green ink, or the word “green” written in red ink. “The response [of the average person without synesthesia] will usually be ‘Gerrred,’ or ‘Rrrgreen’ so there is an interference effect,” said Dr. Marks. The same test can be used to diagnose whether subjects associate colors with letters based on whether or not they exhibit an interference effect. Assuming that a synesthesiac sees the letter A as red and the letter B as green, the test then includes the letter A printed in green and red, and the letter B printed in green and red. The synesthesiac—because of the colors he associates with the letters—will take longer to distinguish the green A as an A, and the red B as a B.

Some people see numbers as different colors. For instance, “two” and “four” may have distinct colors, but as Marks explained, “2 + 2 will have the color of four.” In one famous case, the physicist and synesthesiac Richard Feynman saw all the terms in his namesake equation in different colors.

Most synesthesia comes from an auditory stimulus that stimulates a non-auditory sensation. For example, some people may get a certain taste in their mouth when they hear a specific word. This could be caused from hearing a word numerous times as a child, and each time having a certain taste in mind. Later on in life, whenever the word is heard, the taste associated with that word is involuntarily experienced.

Another example is when someone hears the musical note C, and sees the color blue. When that same person hears a higher- or lower-pitch C, he will still see blue, but it will be a different shade. This may actually help a person have perfect pitch because he can relate the pitch to the specific color. “No one has proven a connection between perfect pitch and synesthesia. They could be different genes that happen to co-occur,” said Marks. There is no agreement among researchers if synesthesia promotes creativity, though it may aid memory.

It is not known for sure what causes synesthesia. “A lot of people think there is a genetic basis because it tends to run in families, but families tend to have common environments, and the environment may also have an impact,” said Marks. One popular theory is that there are extra neural pathways in the brain of a synesthesiac that cause a removal of inhibition. Most theories include some kinds of cross connectivity in the nervous system, but research has been inconclusive. Whatever the cause, synesthesia definitely has experiential components, because it can happen after birth. Studies have shown that the condition can increase in intensity up to five or six years of age. At the same time, some people can have synesthesia as children and lose it as adults. Another interesting fact is that synesthesia in the blind is only present if the person could see at one time; it is not possible in people who are blind from birth.

Most advances in synesthesia research will come from developmental work with children. As Marks explained, “It’s very hard to assess. It’s hard to do good tests in children. There is basically no research money for it in the US.” The American system of grants is such that there are very few grants given, but those that are awarded entail large sums of money. Synesthesia research is currently being done in Canada, where the grant system is such that many grants of small amounts are given out.

The best way to find a child with synesthesia is to find couples with synesthesia that have just had children. They need to be willing to test their children and try to catch the synesthesia as they grow up. “It’s hard to do research without substantial resources. Being lucky is really important,” said Marks.

It is not likely that someone can forcibly develop synesthesia. People have tried to perform Pavlovian conditioning, trying to get students to see a color when they hear a tone. The students would be put through thousands of iterations of a tone followed by the presentation of a color. Afterwards, when the students listened to just the tone, Marks said, “They could imagine the color, but most didn’t see the color.”

No matter what role is played by the environment, synesthesia is reliant on brain wiring as well. The condition has been reported in patients after a brain injury and after the use of psychoactive drugs. There are inhibitory circuits in the brain that suppress activity, and when the drug or injury releases that inhibition, certain neural pathways may become functionally connective. These pathways can effectively short-circuit and misfire, causing a secondary sensation concurrent with a stimulated experience.

Researchers continue to be fascinated by the phenomenon of synesthesia, but the artistic world has also been long drawn to the concept of simultaneous sensations. Records show that in the earliest multimedia concerts in Paris, odors were blown into the concert halls at specific points in the musical score. Prometheus, a short symphony by Alexander Scriabin, was designed to have specific colors shown with the music, like a psychedelic light show. The beginning scenes of Fantasia include artists’ representations of musical notes as the trepidation and color changes of a vibrating chord. Scientifically speaking, Isaac Newton was interested in the relationship between colors and music, and, as Marks pointed out, he was responsible for identifying the existence of exactly seven primary musical notes, and seven primary colors.

Synesthesia appears to be a purely human condition. Marks said, “I’m not sure non-human animals have synesthesia. It is a cognitive phenomenon that requires learning, culture, and experience. It is based on interpretation and context.” Even though it may seem fantastic to hear colors, taste sounds, and see every song psychedelically, Marks thought there was no great benefit to having synesthesia. Synesthetes do seem to have one major advantage over the rest of us, though: Through the conjoining of the senses, they necessarily see the world from more than one perspective.