Why do red-green colorblind people see red and green things as more yellow?

[ED1995]

Hello

I don't understand why people with red-green colorblindness see red and green things in a more yellow way. These people have no M cones so the ganglion cells can't be stimulated by M cones and to see yellow there has to be a stimulation of M cones and L cones.

 

[Greg H.]

Actually from what I understand, if they are truly red color blind, they will see red as black, They see mixed red colors, such as orange, as more yellow because they aren't picking up the red portions of the pigment.

 

You can learn more about how it all works here: National Eye Institute

 

Edit to add:

 

Which is exactly what your color lines show - "red" is actually a very narrowly defined wavelength of light - in a red color blind person that would show up as black, and it would gradually lighten towards yellow as you move up to the shorter wavelengths (as indicated in your diagram).

Edited May 20, 2016 by Greg H.

[ED1995]

But if they can't pick up the red portion why do they see yellow, because to see yellow you need red cones and green cones?

[robinpike]

But if they can't pick up the red portion why do they see yellow, because to see yellow you need red cones and green cones?

 

The color cone sensitivities overlap across the visible spectrum of light.

 

A person with non functioning red cone receptors can still detect light towards the yellow end of the spectrum by the proportion of blue to green receptor activation.

 

[Strange]

The other point is that when they see "yellow" it means they are having the same experience as when they look at something yellow. But that does not mean they see the same thing that a normally sighted person would.

 

In other words the yellow they see is not necessarily the same yellow that someone else sees. It just has the same name because it has the same [set of] real-world referents.

 

(Cue endless discussion about qualia.)

Edited May 20, 2016 by Strange

[ED1995]

 

The color cone sensitivities overlap across the visible spectrum of light.

 

A person with non functioning red cone receptors can still detect light towards the yellow end of the spectrum by the proportion of blue to green receptor activation.

 

But to perceive yellow there has to be an activation of green and red cones, but if the red cones can't be activated, how can they perceive yellow? The activation of blue cones and green cones by red light can't explain the perceived yellow.

[Strange]

But to perceive yellow there has to be an activation of green and red cones, but if the red cones can't be activated, how can they perceive yellow? The activation of blue cones and green cones by red light can't explain the perceived yellow.

 

To perceive the range of frequencies that you call yellow, they only need to have active green cones (as you can see from the diagram). When you tell them that colour is called "yellow" then they will say that everything through to (what you call "red") are shades of something called "yellow". After all, that's is what they have been told to call it.

[ED1995]

 

To perceive the range of frequencies that you call yellow, they only need to have active green cones (as you can see from the diagram). When you tell them that colour is called "yellow" then they will say that everything through to (what you call "red") are shades of something called "yellow". After all, that's is what they have been told to call it.

But this figure says that when you want to perceive yellow their has to be an activation of green and red cones and that's also what you see in the diagram. Where the sensitivity curves of the green cones and the red cones overlap, there is yellow.