Saturday, May 8, 2010

Do You and I Experience the Same World?

I know I don't. I'm red-green colour blind, so I don't see what a "normal" person sees. This was a shock that came to me at age 15 when I was in a driver's ed course. They passed around Ishihara colour test pictures. I got a real chuckle out of the guy next to me who was blue-yellow blind. I thought he was faking the results because the test was so obvious but he kept guessing wrong. Then they passed it to me and suddenly I was the butt of the jokes because I was red-green colour blind. I flailed around with wrong answers because the test is set up to purposefully mislead the blind. A cruel trick to separate us from the pack!

But the fact that we can scientifically test and prove that individuals experience the world differently raises the peculiar question: do you and I experience the same world? On the surface "no", but deep down, we share so much experience with enough overlap that for all practical purposes "yes the world is 'objective' and we share it".

Here is a bit from a blog entry on the ScienceBlogs web site written by a molecular and developmental neurobiologist:
Subjective experience poses a major problem for neuroscientists and philosphers alike, and the relationship between them and brain function is particularly puzzling. How can I know that my perception of the colour red is the same as yours, when my experience of the colour occupies a private mental world to which nobody else has access? How is the sensory information from an object transformed into an experience that enters conscious awareness? The neural mechanisms involved are like a black box, whose inner workings are a complete mystery.

In synaesthesia, the information entering one sensory system gives rise to sensations in another sensory modality. Letters can evoke colours, for example, and movements can evoke sounds. These extraordinary additional sensations therefore offer a unique opportunity to investigate how the subjective experiences of healthy people are related to brain function. Dutch psychologists now report that different types of synaesthetic experiences are associated with different brain mechanisms, providing a rare glimpse into the workings of the black box.

One of the best characterized forms of synaesthesia is grapheme-colour synaesthesia, in which seeing or hearing a particular letter or number evokes the experience of a particular colour. One well-known grapheme-colour synaesthete is the Nobel Prize-winning physicist Richard Feynman, who said, "When I see equations, I see the letters in colours." Feynman was a "projector" synaesthete - he automatically perceived the evoked colours in the external space, or "outside world". The quality of the synaesthetic experience can, however, differ markedly between individuals: in "associator" synaesthetes, the evoked colour is perceived internally, or "in the mind's eye".


Romke Rouwe and H. Steven Scholte of the University of Amsterdam now report that these different synaesthetic experiences are associated with distinct underlying brain mechanisms, and that there also are structural differences between the brains of projector and associator synaesthetes.
Go read the whole article. If you are not aware of synesthesia, then this article will open your mind to a whole world that you -- and I -- are missing because we aren't wired in the necessary way. These synesthetes have different wiring in the brain (while colour blindness comes from defective molecules in the cone cell receptors of the retina). I watched my mother struggle with problems after brain surgery because she had left neglect syndrome and cognitive problems with recognizing people (something like prosopagnosia, but I'm safer to simply call it a type of agnosia).

One of my favourite books about this synesthesia is The Man Who Tasted Shapes by Dr. Richard Cytowic. Another interesting book is Born on a Blue Day by the synesthete and mnemonist and autistic savant Daniel Tammet.

My favourite book about prosopagnosia is Oliver Sacks' book The Man Who Mistook his Wife for a Hat.

The world is stranger than we would believe. The wonderful thing about science is that it opens us up to the richness of the real world. I get so tired of religious fanatics who pound on a two thousand year old book and claim that "all truth" is bound in the pages of that book. What a sad, blighted, narrow-minded view of the wonders of the world.


thomas said...

It is very interesting and sort of coincidental that you post this because I have talked about this with my wife to some extent. She introduced me to the idea and I was profoundly intrigued by the whole concept. I will be looking into the links now.. But, I had to at least let you know that I appreciated the post.

RYviewpoint said...

Thanks Thomas, I'm glad you found it topical.

If you combine this with my next post (biological determinism) and you get the scary/interesting idea of how our genes shape us. But I wouldn't get too excited. All the simple and easy one-gene stuff has been isolated. What is left is the multi-gene basis for disease & behaviour & body. And it gets especially complicated when you realize that genes alone don't usually define you (otherwise identical twins would literally be identical down to the day they catch a disease or show a inclination). And I love the wheels-inside-wheels effects of epigenetics. From Wikipedia:

Marcus Pembrey and colleagues also observed in the Överkalix study that the paternal (but not maternal) grandsons of Swedish boys who were exposed during preadolescence to famine in the 19th century were less likely to die of cardiovascular disease; if food was plentiful then diabetes mortality in the grandchildren increased, suggesting that this was a transgenerational epigenetic inheritance. The opposite effect was observed for females -- the paternal (but not maternal) granddaughters of women who experienced famine while in the womb (and their eggs were being formed) lived shorter lives on average.

Notice that this effect does not show up in the sons & daughters. It shows up in the grandsons and granddaughters! And there are sex-linked differences!