Wednesday, March 19, 2008

Seeing Sounds, and Colours from Another World

Synesthesia must have made a splash in the news recently, because all of the sudden it's on everyone's lips. Synesthesia means "together perception" and refers to a sort of crossing of senses. Oddly enough, people who have this condition may taste what they hear or see what they smell.

One common type of synesthesia is grapheme -> colour synesthesia, in which individual letters and numbers appear coloured. Autistic rights and awareness person Amanda Baggs recently posted a beautiful set of images illustrating how she sees the English and Arabic alphabets.

Another common type of synesthesia is sound -> color synesthesia. In this great art video, animator and director Norman McLaren illustrates sound as he saw it.

Perhaps the most surprising phenomena associated with synesthesia is the ability of colour blind people with the condition to experience "martian colours". These are people who lack the necessary photoreceptors to make red-green or blue-yellow discriminations -- however, this deficiency is located in the retina of the eye -- on the opposite side of the brain from the primary visual cortex. Colour blind synesthetes may report colourings of letters or sounds that they don't see with their eyes, colourings that they are missing the appropriate photoreceptors for, "martian colours" as one synesthete notably put it.

See the following article and lecture for the neuroscience to synesthesia as well as some interesting perspective on the origin of metaphor and abstract thought. It's all about the angular gyrus!

Hearing colours, tasting shapes. Scientific American, 2003
Purple Numbers and Sharp Cheese. Reith Lectures, 2003


Ashley said...

So what happens if she is looking at coloured text..?

Rachael said...

Synesthetes are able to see both the "real colour" and the synthetic colour simultaneously.

So she would perceive this text as having a real colour that is black, plus individual synesthetic colours for each letter.

HOWEVER! If we presented the letter "A" with a slight blue tint to Amanda, she might not detect the blue tint and assume that the real colour is white - so there is some interference.

Ramachandran showed this effect in some of his studies on graphene synesthesia.

Chris said...

It really brings out the uniqueness (to us!) of the senses if you think of trying to explain sight to a blind person or hearing to a deaf person. What would you say?

I'd start with the range of sight... "Imagine you could shoot out millions of little hands from your eyeballs in straight lines (no turning corners), and whatever they touch, that's what you can see! Of course, some things that feel different look the same, and some like-feeling things look different. And if there's no light anywhere, it's like the little hands are numb..."

Would a blind person's idea of a straight line be the same as mine??

Daniel said...

That's one of the sight-to-the-blind descriptions I've ever read.