It is quite clear that for most people, receiving light on the retina means having a visual sensation, just as having something come into contact with our skin generates a tactile sensation or receiving sound waves over our ears causes us to hear something. However, this pattern of events is not always so simple.

There are some people who experience a phenomenon called synesthesia , which consists of perceiving sensations originating in various sensory channels .

Where synaesthesia occurs, one type of stimulation evokes the sensation of another. Thus, some synaesthetes can see sounds, while others can taste tactile sensations, etc. For example, one of the best known cases is that of the physicist Richard Feynman, who claimed to see equations in colours , but the range of combinations of sensations which can be produced as a form of synaesthesia is really very wide: sounds which generate flavours, numbers and letters which are perceived as colours, etc.

Why does synaesthesia occur?

A large part of the neuroscientific community studying synaesthesia believes that it is produced by a kind of “cable crossing”. Thus, they propose the explanation that at the moment this phenomenon occurs, v aryan channels of neurons associated with different senses interfere with each other , so that the information from the surrounding environment that arrives through a sensory organ reaches the brain and is transformed into another type of sensation.

Hence, people who experience this see their senses mixed up involuntarily and without being able to consciously regulate this transfer of information from one sensory type to another, and hence also cases may occur in which blind synaesthetes may continue to experience colours when touching, hearing, etc.

Synaesthetes may have a somewhat unique brain

In short, the brain of people who experience synaesthesia seems to have a somewhat different architecture than the rest of the population , although this does not mean that their nervous system is damaged or that they are less capable of living a normal life and autonomously. In fact, because of the automatic and partially unconscious nature of synaesthesia, it is not unusual for a person to have been mixing sensations all his life and not to have realized how peculiar what is happening to him is, or to believe that it happens to everyone.

How widespread is synaesthesia?

Synaesthesia, under its different forms and types, is not something that occurs rarely in those people who experience it, and therefore it is possible that it is well assimilated and considered the normal way of perceiving reality, since it is part of the day to day of many people.

The fact that many people are synaesthetes without being aware of it makes it difficult to calculate the percentage of the population who are synaesthetes, but recently there have been indications that synaesthesia is surprisingly widespread . It could be part of the daily life of 4 or 5 out of every 100 people, much more than was believed at the end of the 20th century, the most frequent type being that of associating days with colours . Moreover, curiously, it is more widespread among people with autism, which in the future may provide clues to understanding the origin and causes of this type of disorder.

Are we all synaesthetes?

Something to keep in mind is that there are phenomena very similar to synaesthesia that are very generalized, which may mean that almost all of us are synaesthetes to a lesser or greater extent .

For example, it is quite normal that we associate sharp, angular shapes with sounds like the letter “k”, while rounded contours are easier to relate to the sound of “b”, even though this does not respond to any kind of logical reasoning. This type of thinking has also been called by psychologists as cognitive biases . You can learn more about this by reading this article:

  • “Cognitive biases: discovering an interesting psychological effect”

The same goes for many other elements of our daily life: we talk about acidic humour , sharp tongues , etc. In case the hypothesis that these phenomena are mild cases of synaesthesia, our understanding of the normal functioning of the sensory pathways would reveal itself as something more complex than we thought .

Bibliographic references:

  • Baron-Cohen, S., Johnson, D., Asher, J., Wheelwright, S., Fisher, S. E., Gregersen, P. K., Allison, C. (2013). Is synaesthesia more common in autism? Molecular Autism, 4(1), p. 40.
  • Simner, J., Mulvenna, C., Sagiv, N., Tsakanikos, E., Witherby, S. A., Fraser, C. Scott, K. Ward, J. (2006). Synaesthesia: The prevalence of atypical cross-modal experiences. Perception, 35(8), pp. 1024 – 1033.
  • Steven, M. S. and Blakemore, C. (2004). Visual synaesthesia in the blind.Perception, 33(7), pp. 855 – 868.