Friday, March 06, 2009

Colorful Senses

Mary is a scientist who has specialized in Vision and Colors. She knows everything there is to know about colors and vision; how we see objects, how light gets reflected, what neurons in the brain decipher the perceptual signals, what are colors, their wavelengths, their nature, their combination, etc. Anything you need to know on colors and vision, Mary has the answers. Yet, Mary herself is an achromat - she has no color vision. She views the world in just two colors; black and white. The cones in her eyes are not defective themselves; the part of her brain responsible for processing the color signals are defective. Of course, with advances in neuroscience and surgery, this can be fixed. Mary is all set for her surgery, curious to know how the world would look, bathed in all the colors she has meticulously studied. Hmmm... why would a scientist who has expansive knowledge of all colors, wonder how the colors would look like to her? Seems like despite knowing everything there is to know about colors, she still doesn't know quite a few aspects about these colors... (Source: "What Mary didn't know", by Frank Jackson)


This is quite a classic hypothetical scenario used by dualists (those who believe in two entities- mind and body, interacting with each other) to spark a debate with the physicalists (those who believe in only the existence of a body and try to explain/reduce mental states through physical states). I am a dualist (else I wouldn't be using the word Mind all over my blog;)). I do believe in an entity that is separate from a physical body, and assert that not all mental states can be reduced to physical states. Therefore I'm sure to bring in my biases as I put forth my views, but argue with me to help me question my biases :)


It's one thing to know about the physical attributes of perceptual stimuli but it's another aspect to feel them for yourself. Mary might know everything about the color green, yet when she sees a palette of colors, she needs her sensory stimuli to know which color is green. Beyond the work of her sensory stimuli (which is reducible to physical states), is a mental state - a feeling that is associated with the color green. This feeling is impossible to be measured and is highly subjective. This subjective qualitative experience of perceptual stimuli is called qualia.


A related aspect is the inverted spectrum problem. My visual experience of looking at green, might be your visual experience of looking at the color red. This can extend to many other experiences. Pain, happiness, taste, smell etc. I can read everything about a vegetable I have never tasted - I might have heard that it tastes sweet, crumbly and hard to chew... yet I wouldn't know the exact taste of the vegetable, and neither would I know what sweet and crumbly are, unless I've experienced them. I can ask millions to gather more adjectives, yet the essence of the taste cannot be verbalized, neither can it be expressed in physical terms. It is a combination of sensory experiences, that are quite subjective. With advances in Neuroscience, one can probably understand the neurons that fire when people eat an apple and can compare that against thousands of samples to statistically prove similarities in patterns. Yet, there is noway for us to prove that the quality of feelings associated with the neurons are the same.


Consider another example - we measure the activity of neurons when a standard bob pin is poked (using a uniform pressure) into 100 individual's arms (let's make this experiment clean by considering a homogeneous sample of same age, same, gender, same weight). The pain measured via the neurons being stimulated might look similar, yet if we are to ask the participants' rating of their pain, it is going to be highly subjective! There is no way to verify person X's feeling of the pain, with person Y's feeling of the pain! Don't they say it's all in the mind?! There are some brave souls out there going through surgery without anesthesia (in the name of hypnosis, but that is a tangential topic).


There is active research on transferring tactile sensations from expert to novice through haptic devices that try to replicate and simulate force-feedback sensations as experienced by the experts. Yet only a diluted extent of parameters are feasible to be measured (and precision is another issue). But let me not get too emphatic. With progress in neuroscience and haptics , maybe qualia can one day be expressed in physical terms. But the impossibility of verifying qualia against different people (unless we transpose from one body to another), still leaves the stone unturned.

6 comments:

oorjas said...

physically knowing all the attributes of something can no way guarentee a person'e personal experience with anything.

we have always been told that sharp objects can cut or fire is hot. but we don't know what it means till we actually experience it.

it is like experiencing an art. one can either pay attention to all the physical things. or feel the essence of it. in case of music if one keeps track of the raag, Taal, Lyrics, instruments being played they might actually miss the feel the song is trying to produce.

as in this case she might know the physical attributes of colours but when she actually sees them what she will experience is purely unique, which cannot be measured. what emotions those coulours bring about in her can never be calculated.

reactons to a sensory stimuli are not based on the facts known. if a new born is given something sour to eat, the facial expressions produced are not learnt but innate. so is with adults.

SUMI said...

With sensory concepts, understanding seems incomplete without the experience. Understanding colours and colour perception merely as a concept somehow feels like no understanding at all; if we have seen a certain two colours, we could however extrapolate and imagine a colour that would be formed by their combination, though we might have not seen that exact colour. Yet, this understanding seems more like a 'real' understanding, despite the absense of the actual colour in question, than knowing colours as concepts and not having seen any colour at all.

I believe in the existence of a body and a mind too, and do not believe in a purely reductionist theory physiological theories, so we can't argue much there.

About the idea that different people may be perceiving a certain colour differently, this occured to me once in high school and since then I have had a hard time explaining the idea to some people. Didn't know it was a concept that had already been thought of...

SecondSight said...

A rather complicated issue.. what really is going on inside another person's head?:) Two random things come to mind.. one is synesthesia, a sort of cross-connection in the brain when people end up associating two unrelated things to each other- for example, the number 9 and the color red. A synesthete could be reading this and see that 9 in a red font! If Mary being an achromat is a problem in her research, what happens if someone can see colors, but their interpretation of them is so skewed that it doesnt correlate to popular perception anymore? does that perception still count?
On that note.. there's this short story by Maugham (I think)- about a man who goes about re-naming all the objects around him (calling a chair a table, and so on..)-until he gets to a point where no one can understand him anymore.. so, does his understanding of these objects still count? :)

Neeraja said...

Oorjas- Very true, I completely agree with you. And the example with the infant is a good one - some aspects are implicitly wired within us... spontaneous responses to physical events.

Sumi - I can't agree more :). Conceptualizing new colors (creativity) is a good example of the need of unique experiences to reach beyond factual understanding. And yes, I too have thought of this color-illusion when I was young (due to Matrix's influence :)), and was pleasantly surprised that it was a documented problem!

SecondSight - Oh yes, I forgot synesthetes! Well, their condition is more of an aberration or an exception. But unarguably their visual experience of colors and numbers cannot be compared to non-synesthetes. Although if I trained my mind to associate colors with numbers, my visual experiences might change accordingly.

Very interesting story! We usually tend to call such people partially color blind, and they believe themselves to be so, for it's impossible for them to argue that they are seeing the colors we are seeing but interpreting them differently! But I wonder what sort of perceptions/interpretations colors can incite? If no one had taught me what are the names of colors, what sort of interpretations would I have of them? Grass will be color X and so will be the color of leaves. But if I called the color of leaves not to be the same as that of grass (since some leaves are of darker shades)I can get into a debate. I could call the darker shade of green as red and people would refute me, although my perception is true! So it's tricky... if a person develops different perceptions of colors he would be an interesting and valued research participant!! :)

Perception said...

This is such an interesting thought. What comes to my mind is how ones happiness can be perceived as some one elses sorrow. But SecondSight's story bring out another thought, is it the way we are taught to perceive things around us, right from childhood that makes us feel about those things?

Neeraja said...

Perception - That's quite true... human emotions are quite subjective. Two people can be exposed to identical circumstances yet due to their unique needs and views, they will surely have different emotional responses. Definitely the environment and nurture feeds into our likes/perceptions/views etc...