Color-blind synesthesia, Evidence for/against the existence of qualia? Options

[brian0918]

Quick summary: There is a person whose eyes don't allow him to see certain colors (color-blindness), but who can perceive those colors due to a condition (grapheme-color synesthesia) that makes him see colors when he sees numbers. Evidence for/against existence of qualia?


I recently read an article on SciAm about an individual discovered by V.S. Ramachandran with the following ability:

"We also observed one case in which we believe cross activation enables a colorblind synesthete to see numbers tinged with hues he otherwise cannot perceive; charmingly, he refers to these as "Martian colors." Although his retinal color receptors cannot process certain wavelengths, we suggest that his brain color area is working just fine and being cross-activated when he sees numbers."


He also discusses it further here:

"The effect is most obvious and pronounced in the colorblind synesthetes, but occurs in "regular" synesthetes as well. The colors evoked by cross activation in the fusiform gyrus "bypass" earlier stages of color processing in the brain, which may confer an unusual tint to the colors evoked. This is important for understanding the phenomenon of synesthesia, because it suggests that the qualia label--that is, the subjective experience of the color sensation--depends not merely on the final stages of processing but on the total pattern of neural activity, including earlier stages."


What do you think of this individual's ability to "see" colors that he can't - and presumably never could - physically see. Is this evidence for/against qualia? Is it simply evidence for the fact that our brains utilize some sort of "spectrum of interpretation" for colors, so that even though these individuals have never seen the colors elsewhere, their brains will interpolate from other data?

Any other thoughts?

[lucid_dream]

this has nothing to do with the existence of qualia and everything to do with whether conscious experience of completely novel sensations can be evoked without receptors for said sensations. I do not believe it possible. It's like asking someone congenitally blind to imagine what it's like to see.

[brian0918]

this has nothing to do with the existence of qualia and everything to do with whether conscious experience of completely novel sensations can be evoked without receptors for said sensations. I do not believe it possible. It's like asking someone congenitally blind to imagine what it's like to see.

Why shouldn't it be possible? These two things are known to be true:

1. The sensory receptors are just the beginning of the process of evoking a color in the brain.

Ramachandran has shown that cross-activations (numbers evoking colors) can occur at multiple points in this process.

2. In grapheme-color synesthetes, colors are being evoked at those points in the brain, without their eyeballs receiving any external light from those wavelengths of light.

I'm not saying that the color-blind synesthete is necessarily experiencing what he would definitely experience if his eyeballs could receive the colors they currently can't; maybe his brain is doing some sort of interpolation based on colors he's already familiar with... who knows... anyways, it doesn't seem unreasonable that regions of the brain that can trigger colors without having any external stimulus from those wavelengths can also trigger colors that we believe the person shouldn't be able to perceive, for whatever contrived reason...

[lucid_dream]

maybe his brain is doing some sort of interpolation based on colors he's already familiar with

interpolating between subtle shades or hues of similar colors is one thing that many of us have experienced or can experience, but extrapolating to completely different types of colors that have never been perceived before is something completely different. There is a wealth of evidence that our perception is dependent on our sensation, and our sensation is dependent on our senses. If you lack the sensory apparatus for sensing certain fundamental qualities, then it is not possible to perceive or imagine these things. Everything we can imagine is anchored in our direct sensations (the idea of which dates back to at least Hume). You cannot imagine anything completely separated from your sensations. So the idea that anyone can do this, I do not believe, or at any rate am extremely skeptical until compelling objective evidence is presented, and that doesn't just rely on subjective reports which are prone to error.

[brian0918]

maybe his brain is doing some sort of interpolation based on colors he's already familiar with

interpolating between subtle shades or hues of similar colors is one thing that many of us have experienced or can experience, but extrapolating to completely different types of colors that have never been perceived before is something completely different.

What's so hard to believe about this? It's not as if the light that hits your eyes is directly involved in your brain's functions; your brain has all the necessary components for creating perception. Assuming that one's only defect is in their eyes, what makes you think their brains would be equally defective at perceiving certain colors, real or imagined.

If you lack the sensory apparatus for sensing certain fundamental qualities, then it is not possible to perceive or imagine these things.

What is this based on? Synesthetes perceive colors without any specific wavelengths hitting their eyes. Astronauts perceive flashes of light without any light hitting their eyes. People on drugs can perceive colors that aren't there. What is this strong evidence you have to be able to say definitely "it is not possible to perceive or imagine these things"?

Everything we can imagine is anchored in our direct sensations (the idea of which dates back to at least Hume). You cannot imagine anything completely separated from your sensations.

Just because the external component of sensation (the eyes, nose, tongue) might not work doesn't mean those same areas of the brain don't work, and as has been clearly shown, those areas can be cross-activated by other areas, leading to the perception of colors associated with numbers. Nothing about your brain requires that your eyes/nose/ears/whatever be connected to it for its individual components to function or potentially function in the future.

and that doesn't just rely on subjective reports which are prone to error.

These reports are anything but subjective. Ramachandran and others have thought up clever ways to determine for certain what these people are perceiving, and in a way that they could not, on average, fake (well, unless there is a world-wide conspiracy among synesthetes). You may want to read some of the literature on this........