Synesthesia (sin-es-THEE-zhee-uh) is a neurological * condition in which the stimulation of one sense automatically activates another sensory pathway. For example, hearing music may cause an individual to see color. Synesthesia is not considered a mental health disorder and is not listed in DSM-5 * because it rarely interferes with activities of daily life.
Lauren was in the first grade when she asked her music teacher if they could “sing the green song.” Her teacher was confused. She thought about the songs that she had taught the children. None of them mentioned the word “green.” None of them were about the environment. Finally, she asked Lauren which song she meant. Lauren sang a few bars of the song, which was about a dog. The teacher was still confused and asked Lauren why she called it the green song. Lauren explained that when they sang it, she saw the color green. Lauren had sound-to-color synesthesia, but she had not yet understood that she sensed the world in a way that was different from most people.
Synesthesia is a neurological condition in which two or more senses are simultaneously activated by a stimulus that would normally activate a single sense. The word synesthesia comes from two Greek words that mean “together” and “perception.” In other words, two or more sensations arise from a single stimulus. For example, when a person with synesthesia hears music, he or she might also perceive colors. The activation of multiple senses is automatic and occurs simultaneously. People who have synesthesia are called synesthetes (sin-es-THEETS).
Any two or more senses can be linked in people with synesthesia. Some synesthetes feel music as a physical touch. Others hear everyday sounds such as a doorbell ringing or a dog barking as a particular color. The taste of certain foods, such as chicken or chocolate, may be described by a synesthete as having specific shapes. The author Joanne Harris has said that certain colors cause her to smell specific scents.
Many synesthetes perceive words or letters as having a specific color. “Car” maybe always be blue or the number “8” orange. The color of a number or letter varies from one synesthete to another. The number 8 may be orange to one person, green to another, and pink to yet another. However, in any individual, the color, shape, feel, or taste caused by a particular stimulus remains the same. In addition, the intensity of the experience varies from person to person but normally remains constant in each individual.
Much research was done on synesthesia from the mid-1800s until about 1930, when interest in the subject declined. In the 1980s technology provided new noninvasive ways to look at what happens in the brain, and researchers again became interested in studying synesthesia. As of the 2010s, scientists believe that there are two general forms of synesthesia. In the projective form, people actually see different colors or spatial relationships among words or numbers, or they physically feel sensations. In the associative or personification form, people connect a certain stimulus with a color or feeling.
For example, music played in the key of B-flat may cause a projective synesthete to see the color blue, while an associative synesthete would strongly associate the music with the color blue, but not actually see the color. The color that an individual associates with a particular musical key or note varies from person to person. Franz Liszt (1811–1886) and Nikolai Rimsky-Korsakov (1944–1908), both composers and both synesthetes, are well known for arguing over the color of various musical keys.
Although any two senses can be linked—for example, touch can stimulate the sense of taste or smell—some associations are more common than others. Researchers have identified the following types of synesthesia.
Studies have shown that most people with synesthesia consider it a bonus or a gift, not a handicap. Many synesthetes say that the condition causes pleasurable feelings, although a few experience negative emotions. When asked if they would prefer to not have the condition, most answer no. Some go so far as to say they would feel like they were losing a part of themselves, like an arm or a leg, if the condition disappeared. Young children with synesthesia consider it perfectly natural and often are surprised to discover that other people do not experience the same linked sensations that they do.
The intensity of the experience caused by synesthesia varies considerably from person to person. Some forms of synesthesia allow people to remember events, sequences of dates, numbers, or letters with ease. Synesthesia is especially common in creative people such as musicians, artists, and filmmakers. Musicians with sound to color synesthesia are more likely than other musicians to have perfect pitch. People with grapheme synesthesia make excellent proofreaders because a word that is spelled wrong stands out as being the wrong color.
Synesthesia is a congenital * condition, although it does not become apparent until childhood or later. Researchers believe that multiple genes are involved in its development. The disorder tends to run in families, but the inheritance pattern is inconsistent. The condition can skip generations or develop in people who have no relatives with synesthesia.
Scientists are able to use a special form of magnetic resonance imaging (MRI), a noninvasive procedure that lets them identify which parts of the brain are active at a given time. They have found that the brains of synesthetes show a different activity pattern than nonsynesthetes. For example, people with sound to color synesthesia show activity in the visual cortex, the part of the brain that processes incoming sight stimuli, which is not present in nonsynesthetes.
As of the mid-2010s, there are two main theories about synesthesia and the brain. One suggests that synesthetes have more nerve connections between specific parts of the brain that process different stimuli than nonsynesthetes. The other suggests that the condition arises because of a failure to block certain feedback in nerves of the brain that normally is inhibited in nonsynesthetes.
Synesthesia is very hard to fake. To be diagnosed with the disorder, a person must meet most of the following criteria:
Synesthesia is not a disease or a disorder that can be prevented or that needs treatment. It is a lifelong neurological condition. Most people who have the condition find it natural and not disruptive to their daily activities.
See also Autism Spectrum Disorder
Banissy, Michael, Clare Jonas, and Roi Kadosh. “Synesthesia: An Introduction.” 5 Frontiers in Psychology (15 Dec. 2014):1414 doi: 10.3389/fpsyg.2014.01414 (accessed July 13, 2016).
Leatherdale, Lyndsay. Synesthesia: The Fascinating World of Blended Senses. Dublin, Ireland: IMB Pub., 2013.
Neuroscience for Kids. “What Is Synesthesia?” University of Washington. https://faculty.washington.edu/chudler/syne.html (accessed July 13, 2016).
American Synesthesia Association. 75 E. 4th Street, Ste. 573, New York, NY 10003. Website: http://http://www.synesthesia.info (accessed July 13, 2016).
* neurological refers to the nervous system, which includes the brain, spinal cord, and the nerves that control the senses, movement, and organ functions throughout the body.
* DSM-5 is the Diagnostic and Statistical Manual of Mental Disorders, 5th edition, published by the American Psychiatric Association. This book is used by physicians in the United States to classify and diagnosis of mental conditions.
* hallucination is an experience which involves the perception of something not actually present.
* congenital (con-GEN-it-al) means present at birth.