No two brains are wired exactly the same way, and, therefore, everyone’s reality is also different. This doesn’t mean that the physical world is different or that it doesn’t exist. But the way the world is perceived by everyone is different. This concept can be jarring, and for many years it led to differences in perceptions being regarded as fictitious.
Take for example “synesthesia” which is a state in which two or more senses are connected in ways that some people experience perceptions that are different from the majority of people. As recounted in Dr Richard E Cytowic’s illuminating book Synesthesia (published by The MIT Press) until a few decades ago, people who claimed to have one of the 150 or so different kinds of synesthesia were ridiculed by the scientific establishment.
More modern acceptance of the phenomenon is in great part due to Cytowic’s own research. “A synesthete, as we call these otherwise-normal individuals, might not only hear my voice but also see it, taste it, or feel it as a physical touch… Because they are often ridiculed or disbelieved, they tend to keep their extraordinary perceptions to themselves,” writes Cytowic.
And now, it is estimated that around 4% of the population has the basis for some form of synesthesia. Then, social experiences in early life allow combined associations to be further developed. In fact, synesthetes are often surprised to learn in early childhood that they perceive the world differently from others.
In Wednesday Is Indigo Blue, Cytowic and neuroscientist David Eagleman bring to light other cases of synesthesia. Seeing days of the week in colours seems to be one of the most frequent forms of synesthesia. Along with colourful representations of numbers and letters, these are known as graphemes.
Someone else might experience a voice as a sound or a physical touch. In The Man Who Tasted Words, Dr Guy Leschiziner describes a man who experiences different tastes at different London Underground stations. Passing through Tottenham Court Road, he tasted eggs, sausage, and toast.
While this form of synesthesia is relatively uncommon, it is not unheard of. The Russian mnemonist Solomon Shereshevsky could not read newspapers while eating breakfast because the taste of words interfered with that of food. Shereshevsky also had an incredible memory, and this inability to forget interfered with his daily life.
Can you or I get synesthesia if we don’t have it already? It is unlikely. Most synesthetes are born with this capacity (though a few acquire it after brain injury or stroke). A crucial component of synesthesia is that once associations are formed, they do not change over time. They are lifelong. Someone who sees the number nine as pink will always see it as pink.
Synesthesia is not a disease. Rather, those of us who lack this superpower should be thankful for synesthetes for showing the wide range of human experiences that are possible.
Very early in life, many parts of an infant’s brain are connected. Some of these connections will be maintained throughout life. Others will be pruned. A brain has to be assembled, but in the process, it also disassembles itself. How a brain develops depends not only on the genes that are inherited, but also on experiences. The brain remains hyperconnected, but differences in brains can lead to differences in perceptions.
Much remains to be learned about synesthesia, including what purpose these traits serve and why they have been kept in the human gene pool. Cytowic believes that synesthesia in all its manifestations is a genetic embodiment of the human capacity for metaphors. “We all share the same world but a different texture of reality,” he writes.
Curiously, one study found that synesthesia is seven times more common among artists than in others. A number of artists are synesthetes including Vladimir Nabokov, Franz Liszt, Stevie Wonder, and Lady Gaga.
Acceptance of synesthesia shows how far neuroscience has come. It was thought only a few decades ago, that the brain consisted of distinct modules. Now, we know that there is an enormous amount of cross-connection in the brain. Senses are not all separately formed and disconnected from one another. They are connected in all of us, and in synesthetes, they’re connected in exceptional ways.
Anirban Mahapatra is a scientist by training and the author of a book on COVID-19
The views expressed are personal