The cross-wired brain
When Jane looks at numbers she experiences colors. As each number has its own fixed colored overlay, this quality makes the recollection of phone numbers so much easier. John on the other hand has “colored hearing”, his hearing and visual cues gets crossed when it comes to musical notes. He sees white when he hears the note C, bright-yellow when he hears E and orange when he hears A, making each song a colorful adventure. There are also people who experience flavors without their taste buds coming into contact with any substance. For them some words have distinct flavors, which has a big impact on various parts of their lives. Imagine reading a book and experiencing an array of flavors at every sentence. Different textures elicit different emotions for some people. Velvet might elicit feeling of sadness, porcelain jealousy and steel shock. Last but not least, faces elicit color for some people and sometimes these colors form a halo around the face. No, they are not psychics seeing people’s auras, they are synesthetes.
What all these people have in common is not a neurological disorder, but some kind of mixing of sensation, perception and emotion, a condition called synesthesia. People with two or more senses coupled in this way are called synesthetes. Synesthesia receives it’s name from the greek word σύν (syn) wich means “together” and αἴσθησις (aisthēsis), wich means “sensation”. There are many kinds of synesthesia, in fact almost any cross-blending of the senses is possible.
Most synesthetes claim to have had this condition as long as they can remember. Their experiences are involuntary, automatic and constant, i.e. they have no control over it and their associations are fixed. If a number has a color attached to it, the color will be the same throughout life. The majority of synesthetes wouldn’t dream of parting with their synesthesia, even though it can at times be unpleasant, such as when nausea arouses because of a nasty vile-tasting word.
The synesthetic brain
In healthy newborns, there are pathways between brain areas that get eliminated through a process called pruning as the brain matures. According to both Richard E. Cytowic and Vilayanur S. Ramachandran, leading pioneers in synesthesia research, this pruning is incomplete in synesthetes, so there are connections, cross-activation, between areas in the brains of synesthetes, that are not present, or present to a lesser degree in non-synesthetes. Everyone is therefore born synesthetic, only to lose the capacity when the brain matures.
Here is a video from YouTube: A man who sees colors in letters and sound:
Here is a wonderful video on some kind of artificial synesthesia, a totally colorblind man perceives color through hearing: http://vimeo.com/51920182
Cytowic, R. E. (2002). Touching tastes, seeing smells—and shaking up brain science. Cerebrum, 4, 7–26.
Hochel, M & Milán, E. G. (2008). Synaesthesia: The existing state of affairs. Cognitive Neuropsychology, 25: 93–117
Ramachandran, V.S. (2011). The Tell-Tale Brain: A Neuroscientist’s Quest for What Makes Us Human. New York: W.W. Norton & Co.