Some people perceive numbers or tones as colors – behind this is a hardly researched phenomenon
On the website of the German Synaesthesia Society this scene from the movie Ratatouille is mentioned as an example for synaesthesia. Pixar / Disney
When Alexandra Kirschner thinks of numbers, letters or certain words, colors appear in her mind’s eye. And Alexandra Kirschner’s life is more colorful in other areas as well. Every day of the week has its own color for them, which always appears in the same way. Monday red, Saturday black and Sunday light blue.
Alexandra Kirschner is a synaesthete. It perceives sensations partly coupled. When she hears a noise, sounds or music, colors appear in her mind’s eye. They often come from the same direction as the sound or noise, she explains. If the sound comes from the back left, she sees the corresponding color in her left visual field.
Synaesthetes often do not notice for a long time that not everyone perceives stimuli in a coupled way
Synesthesia is not a disease. It concerns rather a perception phenomenon. Scientists currently assume that about four percent of people are synesthetes. However, it is difficult to say how often synesthesia really occurs. Because these coupled sensory perceptions are the reality for synaesthetes. They perceive it as completely normal and don’t know it any other way.
Alexandra Kirschner, for example, realized that she is a synaesthete only in her early 40s. Her key experience: an article about synesthesia. The headline said it: When the seven is blue. „Then a protest arose in me and I thought: ‘Wait a minute, the seven is yellow’.", says Alexandra Kirschner.
Colors are particularly often perceived when listening
„Often synesthesia occurs in the visual or auditory area", explains Gregor Volberg, who is working on the topic of synaesthesia at the University of Regensburg. According to him, synesthesia is particularly common, in which those who hear colors or feel colors to tones. In the so-called grapheme-color synesthesia, which many synesthetes have, numbers or letters are associated with certain colors. However, the classification varies from person to person. For one person the seven is yellow, for the other green.
But this is not the only form of synesthesia. When hearing in color, synesthetes perceive colors and shapes, for example, with noises, sounds or music. Other synaesthetes, on the other hand, classify time units spatially or perceive other stimuli in addition to people, smells or tastes. „It’s fairly typical for people who have one form of synesthesia to have other forms as well", says Volberg.
Subtitles in real life
Ruth Regehly is also a synaesthete. Especially with music and sounds she perceives colors and also structures. Different musical epochs have different color palettes for her. Instruments feel different, the stimuli associated with them behave differently in space. When Ruth Regehly sees paintings, sculptures or textiles in which she considers the artistic quality to be high, she perceives it as taste- „tart and fruity, like a very good white wine", she says.
Additionally she has a grapheme-color synesthesia. She remembers combinations of numbers, such as passwords, as a sequence of colors. This is easier for her. In addition, the so-called ticker-tape synesthesia occurs with her. She practically sees subtitles to the spoken words and can read along. „It makes it easier for me to deal with older people. When they mumble, I can read what they probably mean", she says. Practical, because Regehly works as an everyday companion with elderly people.
Words have a pattern for her. If the spelling is not correct, the pattern looks wrong to her. She is happy when she finds out what is wrong with the pattern, for example when proofreading. Colors and textures also appear to her with physical sensations. She first noticed this with pain, she remembers. „I can gauge the nature of the pain by the color and its intensity.“
Sometimes the stimuli are too much
Alexandra Kirschner says she has 16 forms of synesthesia. According to the expert, this is a lot. She not only sees colors to numbers, some letters and punctuation marks, but also days of the week and months are colored. Temperatures have colors or structures with her, pain colors, shapes and partly a taste. Even with some words or sounds, a taste that has nothing to do with food fills her mouth, as it does with a few sounds. When Alexandra Kirschner hears a computer mouse click, it tastes slightly metallic in her mouth, she says. In addition, some smells appear colored to her.
This often has advantages, says Kirschner. She uses the additional perceptions, for example, in her work as a voice coach. She sees, she says, the quality of the voice in front of her. For her, high-pitched voices tend to be orange-yellow, while low-pitched voices are blue or brown. She can also see which sound does not fit into the picture. This can be used for individuals as well as for vocal groups. „The wrong sound then becomes kind of gray or foggy or dark", she describes. „Or it hangs out in the scale and is not on the same line up as the other tones.“
Due to the fact that synaesthetes feel many stimuli, they may also experience stimulus overloads. Moreover, synaesthetes sometimes have problems with their attention or even orientation. „It only bothers me when numbers or letters are displayed in wrong colors. I find that quite terrible", says Alexandra Kirschner. Because numbers have a certain color for her, she already had orientation problems in the suburban train. The reason: The numbers of the respective S-Bahn lines were assigned different colors than in her case. „There I really got confused", she remembers. Also, when there was a disco next to her apartment, it wasn’t always easy, she says. In the evening she not only heard the bass and loud music when she wanted to sleep, but in addition to that she felt colors.
Ruth Regehly is also sometimes confused by her synesthesia, for example when working in a nursing home. „Sometimes I get confused because the colors are assigned to the floors, but they don’t correspond to the colors I have", she says. In everyday life she sees colors through her synesthesia when she hears something. This also happens with noises she doesn’t like: "My refrigerator hums quite loudly in an ugly brown.“ Whether a sound has a color that she finds beautiful or ugly does not depend on whether she likes the sound or not.
Synesthesia is visible in the brain
The causes of synesthesia are currently still unclear. „It may be that the different synesthesias have different causes", says Volberg. He says the various synesthesias are often not treated as a global issue. Instead, scientists do research on their particular perceptual area. Some are more concerned with visual perception, i.e. what we see, others with what we hear.
„Overall, synesthetes seem to have higher connectivity. So different areas of the brain work together more in them", he explains. But this does not necessarily have to be due to more neuronal connections. Thus, synesthetes show more small, local and less global connectivity. So a lot of little modules in the brain like to work together. Higher activity between different brain areas can be seen on MRI, for example.
Synesthesia could be a memory phenomenon
„Alternatively, it could be a memory phenomenon", says Volberg. Non-synaesthetes, for example, recognize different objects as such, even if they don’t always look identical. So cups can have different colors, sizes and also forms and you recognize it from different angles nevertheless as cup again. According to the expert it could be that this is more pronounced in synesthetes. There is an approach that synesthetes have unconsciously learned the colors of letter and number refrigerator magnets and now assign them to the corresponding numbers and letters. „The concrete color assignment to letters is definitely learned, because literacy is a cultural achievement and not innate", says Volberg.
Another approach is that the coupling between stimuli is present in fetuses and is not regressed in synesthetes. What is striking is that synesthesia is probably more common in women than in men. In addition, scientists assume that synesthesia is probably hereditary due to accumulations in families. „A tendency to synesthesia is probably passed down through the female lineage.", says Volberg. A field in which research is still at the beginning. There are still few studies on genetics and synaesthesia, often the case numbers are small.
Ruth Regehly realized early on that people have different perceptions. However, Ruth Regehly only realized that this does not mean that everyone also assigns or additionally perceives colors when she was already an adult. In the beginning, she still doubted and wondered if she was just learning her synesthesia, she recalls. „But against it speaks that my feeling resists against other colors", she says. When she was a child, she once drew all the numbers from zero up to and including nine. Each number in a different color. The three had become pink. A color that Ruth Regehly did not like. But when she wanted to paint it in a different color, it just felt wrong. After all, the three is pale pink.
She can tell about her synesthesia, but she cannot make it visible to anyone. Sometimes it’s confusing for her, but in general Ruth Regehly sees synesthesia positively and as another way to orient herself. „Synesthesia and high sensitivity sometimes give me a sensory overload, but I wouldn’t give either of them away.“