Are there people who can hear colors and see fragrances? The amazing "pathway" in the brains of "synesthetes"

On the evening of November 11, the 12th Pineapple Science Award Ceremony was held in Wenzhou, Zhejiang. The research team led by Dr. Ryan Joseph Ward of the University of Liverpool in the UK won the Psychology Award of this year's Pineapple Science Award for their research on "The Impact of Smell on Color Perception".

Wait a minute, isn't it smelling? Isn't it seeing? What's the connection between smelling and seeing? You heard it right, there is a group of people called "synesthetes". They may "hear colors" and "see fragrances". Or maybe, when they are in a concert hall, the melodious music in their ears turns into a rain of flowers in front of them... What kind of people are synesthetes? This starts with "synesthesia".

01 Synesthetes: You don’t have to be an “expressive person”, just because your senses have the “strength” to do so

Synesthesia, also known as synesthesia, refers to the phenomenon that the senses such as hearing, vision, taste and smell affect each other . It is a rare characteristic of the nervous system, not a disease or disorder . In 2006, Simner and her colleagues at the University of Edinburgh interviewed nearly 1,700 subjects and tested consistency. Certified synesthetes accounted for 4.4% of the group, or 1 in every 23 people.

There are many forms of synesthesia. At present, there are more than 80 kinds of synesthesia combinations. For example, graphic-color synesthesia, sound-color synesthesia, taste-shape synesthesia, number-character synesthesia, etc. Synesthetes with synesthesia can perceive and express their impressions and emotions about things through different senses . For example:

(1) Character - color synesthesia

This type of synesthesia is the most common . People with this type of synesthesia associate symbols such as letters, numbers, or musical notes with specific colors : the letter A may be red, the letter B may be blue, the letter C may be yellow, and so on. These colors are not random, but are determined by personal experience and memory. Therefore, each synesthete has his or her own unique color coding, and these codes are usually fixed in childhood and difficult to change.

Examples of synesthetes associating colors with letters and numbers (Image source: Wikipedia)

(2) Taste-shape synesthesia : A taste-shape synesthete can use shapes to describe different tastes , for example, saying that one taste is round and another taste is triangular.

Taste-shape synesthesia example: the shapes of dairy products: cow's milk, goat's milk, coconut milk, yogurt, cheese, butter, ice cream and cream. (Source: Susan Brice in the Gallery of the website sensequence.de)

(3) Number-personality synesthesia : A number-personality synesthete can use personalities to describe different numbers , for example, 1 is brave, 2 is gentle, and 3 is lively.

0 2 "Synesthesia Art" draws a shining trajectory in the long sky of history

Although synesthesia is rare, it has existed throughout history and is inseparable from the images in art and literature, so much so that a special field called "synesthesia art" has emerged - that is, artistic exploration using "synesthesia experience" to help explore human survival experience and understanding of "synesthesia". Here, "synesthesia experience" can refer to the several common classic patterns mentioned above, as well as all cross-sensory experiences with a broader meaning, including conceptual synesthesia , which belongs to the category of neurocognition.

China has had synesthesia since ancient times. The story of "High Mountains and Flowing Water" in the pre-Qin period is an early example of synesthesia: Boya played the zither and thought of the mountains. Ziqi listened and exclaimed: "Great! The sound of the zither is like the majestic Mount Tai standing before my eyes!" Boya thought of the flowing water, and Ziqi said: "Great! The sound of the zither is like a rushing river flowing before me."

We can also feel the beauty of synesthesia in Chinese classical poetry. Wang Wei, a famous Tang Dynasty poet, made good use of "synesthesia of sound and picture", such as "When people are idle, sweet-scented osmanthus flowers fall, and the night is quiet and the spring mountains are empty. The moon rises and startles the mountain birds, which occasionally sing in the spring stream." This poem describes a quiet spring night. The moon rises, and the mountain birds are awakened, occasionally chirping, and the sound echoes in the empty mountain stream, forming a vivid picture of sound and picture.

There are many synesthesia artists around the world, and the famous painter Vincent Van Gogh is one of them. In 1881, he said in a letter that some painters have extraordinary talents and can use their hands as skillfully as violinists. He also believed that the works of these painters are "pure music". This suggests that colors and music are related in Van Gogh's mind.

Van Gogh (Source: Tuchong)

In 1885, when Van Gogh began to learn piano, his identity as a synesthete became clearer. After a few lessons, Van Gogh felt strange - he felt that each note was stirring up a precise color. Although he was a synesthete, his works are not the kind of art that is obviously synesthetized. However, some synesthetes claim to hear sounds of joy and hope when looking at the unrestrained painting of sunflowers.

Van Gogh's "Sunflowers" at the National Gallery, London (Source: Visual China)

0 3 The formation mechanism of synesthesia is still undetermined

In 1881, Darwin's cousin Francis Galton described the first case of synesthesia in the journal Nature, and research on synesthesia has been ongoing ever since.

Number forms are mental maps of numbers that appear automatically and unconsciously whenever a person experiencing number form synesthesia thinks of numbers. These numbers may appear in different locations, and the mapping varies from one individual to another. Number forms were first documented and named in 1881 by Francis Galton in The Visions of Sane Persons. (Source: Wikipedia)

Callejas, a researcher at the University of Granada in Spain, believes that synesthesia is caused by extra connections between different brain regions . Normally, the brain regions responsible for processing different sensory information are separated from each other, but the brain regions for different senses are close to each other. In the brains of synesthetes, these regions have more communication and interaction. This leads to the activation of certain brain regions, which in turn drives the activation of other brain regions, thus producing the synesthesia effect .

In 2001, a study by the Center for Brain and Cognitive Research at the University of California, San Diego, added further evidence. The study showed that the V4 area of ​​the brain processes information related to color analysis. The V4 area is located in a spindle-shaped gyrus area, which also produces a concept of the shape of each number. The researchers believe that the phenomenon of number-color synesthesia may be the result of cross-activity between the V4 area of ​​the brain and adjacent areas.

Areas thought to be cross-activated in grapheme-color synesthesia (green = grapheme recognition areas, red = V4 color areas) (Source: Wikipedia)

Later, some studies clearly pointed to the influence of genes . In 2018, neuroscientists Simon Fisher and Amanda Tilot from the Max Planck Institute for Psycholinguistics in Germany used genetic data from synesthetes' families to study and discovered DNA variants in synesthetes. Using gene sequencing, the researchers identified 37 genes that indicate a tendency to synesthesia, and no single gene was seen between different groups, confirming that the inheritance of synapses is not related to just one gene or a group of genes .

The study of synesthesia has also begun to connect with cutting-edge research on consciousness. In 2017, philosopher of mind Myrto Mylopoulos of Carleton University in Canada and neuroscientist Tony Ro of the City University of New York said that because different forms of synesthesia involve all sensory and cognitive elements , synesthesia research can test a wide range of theories of consciousness.

Author: Yiyi, Master of Applied Psychology, University of Chinese Academy of Sciences

Reviewer : Tang Yicheng, editor of the National Psychological Service Grassroots Collaboration Network, deputy secretary-general of the Psychology Popularization Working Committee of the Chinese Psychological Society

Produced by: Science Popularization China

Produced by: China Science and Technology Press Co., Ltd., China Science and Technology Publishing House (Beijing) Digital Media Co., Ltd.