Synaesthesia: The interconnection of the senses

Synesthesia in psychology
  • Come on son, we must continue with the calligraphy duties. Grab a pencil
  • Ok…

Marco, with an expression of doubt, looks at the pencil-case, where there were pencils, pens and coloured pencils, all mixed together. He picks up a pencil slowly, looks at the mother and asks

  • A pencil you said?

The mother, strangely, looks at him and says

  • Yes darling, we have to be able to erase if we make a mistake.

Marco, who understands what his mother is saying, nods with greater conviction and grips the pencil more tightly. Open the notebook and start copying the sentences from the exercise. After a few minutes, Marco asks:

  • Mom, I don’t understand… Why should I write with the pencil? Look, for example, the word “cow” is not right like that, it is brown… and with the pencil it is gray.

At first, Marco’s mother is not quite sure what she has just heard, but in a few seconds she reacts and asks Marco:

  • What do you mean it’s brown? What do you mean, Marco?
  • Well, that’s brown, because the “O” is brown, so “cow” is also brown.
  • I understand…

If you don’t understand anything when you read this dialogue, it’s probably because you’re not a person like Marco. Don’t worry, nothing bad happens to Marco, he is just a child with grapheme-colour synaesthesia. Marco’s brain associates letters with colours so strongly that he even feels like he can see them. Indeed, he doesn’t see them, Marco knows that they are only in his head, but he still believes that others perceive them the same way he does.

For everyone to understand, and saving a lot of differences, it is like when we have looked at the sun and then we see certain coloured nebulae in our field of vision. We all know that it is an effect of light, that it is a matter of our eyes, but we see it anyway. The same happens with the coloured letters that Marco perceives. An important difference is that Marco has these associations well structured. He always perceives the letters of the same colour. For example, if we look at vowels, for Marco the A is white, the E is green or blue, the I is orange, the O is brown and the U is black, always the same.

Synesthetic experiences are idiosyncratic, meaning that each synesthetic person can have unique and different perceptions. For example, one person may see the number 7 as yellow, while another may see it as blue. These perceptions are not mere associations, but real, vivid sensory experiences.

What is synaesthesia?

Synaesthesia is defined as the ability to perceive sensations from different senses together or cross. It is not simply an association of ideas, but a real and tangible perception. For example, a synesthete person may see a specific colour when listening to a musical note or feel a particular texture when tasting a food

What is synaesthesia?

Types of synaesthesia

There are several types of synaesthesia, each with its own unique characteristics. Some of them are:

  1. Grapheme-Colour Synaesthesia: This is the most common. Letters and numbers are perceived in specific colours.
  2. Music-Colour Synaesthesia: Musical sounds evoke the perception of colours.
  3. Lexical-Gustatory Synaesthesia: Words evoke specific flavours.
  4. Tactile-Visual Synaesthesia: Tactile textures cause the perception of colours or visual shapes.
  5. Auditory-tactile synaesthesia: Some sounds evoke tactile sensations
  6. Tactile-gustatory synaesthesia: Some textures evoke flavours.

Causes, explanations and development

Although the exact cause of synaesthesia is not fully understood, it is thought that it may be related to a cross-activation of adjacent areas of the brain that process different sensory information. There is also a genetic component, as synaesthesia tends to be more common in certain families.

There is also some evidence that in the early years of age, this synaesthesia is widespread in all babies. The interconnections between different brain areas are much more frequent at the beginning of our lives and as the brain grows, the different areas of the brain become specialized and this interconnectivity becomes less pronounced. That is why some adults claim to have been synesthetes as children, and not as adults. Even so, it does not usually disappear with age. Most commonly, synesthetic experiences vary in intensity over time. 

Synaesthesia can also occur in an acquired form. In rare cases, it can develop in adulthood due to brain injury, drug use, or intense sensory stimulation. This form of acquired synaesthesia can be temporary or permanent, depending on the underlying cause.

Causes of synesthesia

Related conditions

The association with other Neurological conditions is unclear. Even though it can be an indicator of a neurodiverse mind and require a deeper evaluation, the presence of synaesthesia is not necessarily linked to any condition, difficulty or disorder.

Synesthetes may have a greater ability to visualize abstract concepts and to relate different forms of sensory information. For this reason, we have also tried to see if there was a relationship with high intellectual capacities. However, people with synaesthesia can have any level of intelligence. The condition itself does not appear to be a clear indicator of greater or lesser general intelligence. 

What it does seem to be related to is creativity and artistic skills. It is thought that it may be because synaesthesia can provide an additional source of inspiration and a unique way of perceiving the world. Artists such as Kandinsky and musicians such as Liszt have used their synesthetic experiences in their creative work.

If you think you can be a person with synaesthesia and want to know if it could be related to another condition, you can be assessed by a general health psychologist.

Synaesthesia offers a fascinating window into understanding how the human brain can process information in unique and complex ways. It is one more proof of neurodiversity that characterizes the human mind.

Guillem Nicolau Coll
General Health Psychologist
Nº col.: B-02773