Synesthesia is a neurological phenomenon where one sensory experience is automatically accompanied by another. The most common is colour synesthesia and chromesthesia.
is where for example letters, numbers or weekdays gets a colour automatically “attached”. Tuesdays might be purple, the number 9 red or things like that. It is automatic, involuntarily. People with colour synesthesia can remember phone numbers by colour, solve equations with the help of these colours appearing in the mind. Only rarely does this go both ways. Even if 7 is green, the colour green does not have the number 7 attached to it. Writer and synesthete Patricia Lynne Duffy: ‘One day,’ I said to my father, ‘I realised that to make an ‘R’ all I had to do was first write a ‘P’ and then draw a line down from its loop. And I was so surprised that I could turn a yellow letter into an orange letter just by adding a line.’
People with this ability hear colours. Or maybe more accurate, sounds generates a colour in the mind. They might hear a D major as bright green, but again, as with the colour synesthesia, bright green does not automatically create the sound of a D major. Liszt would confuse his orchestras, enthusiastically correcting them; “No, Gentlemen! Bluer! Bluer!” The neuroscientist Julian Asher was taken to concerts as a child, and he always assumed that the lights dimmed so that people could better see the colours coming from the orchestra.
Synesthetes have no problem differentiating between colours occurring around them and the colour generated in their minds by the numbers or sounds. It is a merging of two senses, and many feels enriched by this phenomena; they know they have two sensory systems sharing the same space. In a way, one sensory input sparks two and create a sixth sense. There are other forms of synesthesia, where colour, names, sounds or letters have taste, where numbers or letters “appear” hovering around in 3D space, or where colour has smell. The key is the combination of two or more senses, based on one sensory input.
I sometimes hear colours, and sometimes sounds gets in the way of seeing. That sounds a little mad, but it seems I am in good company.