Hi, I'm Michael Corayer and this is Psych Exam Review. In this video I want to go over colorblindness in more detail. In the last video,
I mentioned that this term colorblindness is a bit misleading. That's because people who are colorblind, it's not the case that they are blind to
color, it's that they can't see some colors or they have difficulty differentiating certain colors but they still see, in most cases, a very broad
spectrum of colors. So there's different types of colorblindness depending on which cone type is affected. If you look up types of colorblindness
you might initially be a bit overwhelmed by all these different names but there's actually a fairly simple system that these names follow
that can help you to understand these types of colorblindness. Chances are, for an introductory course, you wouldn't be expected
to memorize all these types of colorblindness but if you're interested I thought I'd explain this naming system.
Essentially the naming comes from
the three different cone types. So the first
in this case is red so this is going to use the Greek for first "pro" so we have red
then we have the green, the medium cone, this uses the Greek for second, deuter, and then for the third we have
"tri" in Greek and this is for the blue cone type, or the short wavelengths. So there's two things that can happen to one of your cone types.
One thing that can happen is it can be missing completely.
This is more rare but it can happen, so if you're missing a cone type, we use the suffix "-anopia" which means without vision.
So then we simply this "without vision" to whichever of these cone type is affected. So you could have protanopia, missing the first
cone type, the red. The second type would be deuteranopia, missing the second or medium cone type.
Or tritanopia would be missing the third type.
Then another thing that can happen is that the cone's sensitivity can get shifted and this it the more common
type of colorblindness.
One of the cone types if shifted, usually the red or green.
So if it's your red cone type, the long wavelengths that's shifted it's called protanomaly. If it's the green
it's called deuteranomaly, this is the most common type of colorblindness; deuteranomaly.
Then if it's the third cone type, the blue short wavelengths that are shifted
then that's called tritanomaly.
OK so what do I mean by shifted? What's actually happening here? Let's take a look at
that spectrum that we saw before with the sensitivity for each cone type.
OK so you can see if the green, let's say the green type, were completely messing
you see that wouldn't just affect this green area here, it would influence anything that uses the green cone. So the idea here is, let's imagine
that we only were looking at the red cone here, the longer wavelengths.
How do we tell the difference between this level of stimulation of red
and this little wavelength over here equally stimulates it. So how do we distinguish these two colors?
The answer is we have the other cone overlapping. So if I have this level of
absorption on the red cone but a low level of green then I see it as red. But if I have that
same level of stimulation on that red cone type but I have a higher level on the
green cone type, the mediu wavelength, well that tells me that it's green. Now we can see if one of these is missing, if I'm missing that
green line here now I can no longer distinguish between these two shades and that's why people who have this type of colorblindness
have difficulty distinguishing between green colors and red colors because those are equal stimulation on that
long wavelength red cone. So in the case of anomaly what happens is that
these lines get shifted. So if you have protanomaly
that's an anomaly of the red cone, the first type, the long wavelength, that gets shifted to the left in our diagram. That means the overlaps are
going to be in different places and there's going to be some areas where it's harder to tell the difference between
red and green colors. In the case of deuteranomaly,
which, as I said, is the most common type of colorblindness, it's that the medium cone,
the medium wavelength cone, the green, is shifted to the right.
In some cases it can be shifted where it's essentially on top of the red cone and then you have a really hard time distinguishing colors
because a lot of these red and green shades have basically the same level of stimulation
and so to you they're the same thing.
So that's essentially what happens in this anomaly. Now these red and green
types of anomalies often called red-green color blindness, that refers to multiple types, that can refer to protanomaly, deuteranomaly, etc.
This was first described scientifically by a guy named John Dalton
and he was a chemist and I have a picture of Dalton here. This is why this red-green color blindness is also sometimes called Daltonism.
There's sort of famous stories about Dalton, who was a Quaker,
his colorblindness being apparent because he would do things that didn't quite fit with the
stern, severe Quaker lifestyle that he's expressing quite well in this picture here,
such as showing up in a bright red robe because he thought it was grey, or supposedly
buying his elderly mother stockings which were red when he thought they were actually blue.
OK so on
This red-green color blindness, Dalton noticed his brother was also colorblind, and this suggested that there some sort of
inheritance associated with colorblindness and indeed for red-green colorblindness there is. This is not the case for
tritanopia or tritanomaly but in the case of
protanomaly, deuteranomaly, or protanopia, and deuteranomaly, these are called
this type of colorblindness is called a sex-linked trait.
So what does that mean?
It means it's linked to whether you're male or female.
So if you remember from an earlier video, males, on their 23rd chromosome pair, have an X
chromosome and a Y chromosome whereas females have two X chromosomes.
Here's the male, here's the female.
So what does this mean? Well, the genes for the long and medium wavelength cones are located on the X chromosome.
So what this means is if you have a defective version of the X chromosome, if you're a male let's imagine that's the defect,
then if you have a defective X chromosome then you will be colorblind. But if you're a female and you have that same defective X
chromosome, it's OK because you have another X chromosome that has the correct information. So for a male to be colorblind all
he needs to have is one defect on the X chromosome. For a female she needs to have the defect on both of those X chromosomes
the same defect on both X chromosomes in order for her to be colorblind.
This is why colorblindness is many times more common in males compared to females. Because males, one bad X chromosome and
you're colorblind. Females need to have both X chromosomes have this defect. This also is why sometimes, colorblindness, a common
pattern is for the grandfather on the mother's side to be colorblind and then the
the son to be colorblind as well. So what happened, is the grandfather he has one faulty X chromosome, he gave it to the mother,
who's a carrier, then she has essentially a 50% of giving that to her son,
if he gets that X chromosome, he'll be colorblind.
So that's why we say that colorblindness is a sex-linked trait, remember that's not all types of
colorblindness. So tritanopia and tritanomaly have nothing to do with the X chromosome
and there's also types of colorblindness that occur because of environmental exposure or you could have a random mutation. So it's not
only the case that this is how you are colorblind, but it's the more common situation.
OK so now that the real question that you're probably thinking is "what is colorblind is like?What is it does it feel like to be colorblind, what
does it look like?" So we can look at some examples that will try to demonstrate this to us. You've probably seen something like this
before. This is an Ishihara colorblindness test. The idea here is that if you have normal vision you look at this you see the number 74, but if
you have some version of green color blindness, depending on how severe it is, you might see the number 21.
That's because that this is a written in a way that you can see there's different shades in here and an important idea for this you might
wonder "why don't they just write it normal, why isn't it just solid color?". Well, we want to try to
limit the effects of the brightness. So different colors aren't just different wavelengths they can have different luminances, they have different
levels of brightness and we want to confuse that. We don't want to just be, if it was too solid colors and one is
slightly brighter than the other then you'd be able to see it even if you couldn't see the color. So that's why we have these different
brightnesses, different saturations, so we have different luminance, different saturation, all these mxed up colors here
and that's to ensure that the only difference, the only thing that lets you see the numbers, is the color and not the
brightness of these different colors or the level of saturation or something like that.
We want to ensure it's just the wavelength that's allowing you see the numbers
vs. someone who can't see them. If you have a type of colorblindness you wouldn't just look at one of these slides to determine this. So if you
can't see the 74 here, ok, we know it has to do with the red-green type,
but we don't know exactly what type of colorblindness you have, we'd have to do multiple tests to determine
which, is it the red that's shifted, is the green that's shifted, or is one missing? How much is it shifted? So we'd have to do multiple tests to
determine that and it's also possible but very rare to have
multiple types of colorblindness at once, if we went back for our list here
it could be the case you could been missing more than one, you could have only one cone type. Very very rare but then you'd be very
limited in the colors you see. You could actually have no cones at all, that's also possible, you only have rods. In that case
you only see in black-and-white and it's very blurry, because remember cones allow you to see fine detail.
Also rods don't work very well in the daylight. They're for low-light conditions
so if you have that your vision is going to be sort of overwhelming
blurry because the rods aren't really working at that time.
But in low light you'd be able to see, but it would still be kind of grainy and fuzzy.
OK
I want to mention, you may have seen some YouTube videos of these EnChroma glasses, these are glasses that claim to restore
color vision for people who are colorblind. So how are these working?
Well, first, you have to understand, these don't work if you have an -anopia. If you're missing a cone type they aren't going to be able to do very
much for you. So they're only working for anomaly and usually for the red-green anomaly; protanomaly or deuteranomaly.
OK so up what are they actually doing? Well, they're not restoring color vision. They're not adding any information what they're doing is
they're taking information away, they're filtering out some wavelengths. So we can imagine if these red-green lines were too close together,
let's say we had them overlapping, where we had two points on this line that appeared to be the same stimulation; one that's actually green
and one that's actually red, what these glasses would do is they selectively filter out certain wavelengths.
So if we filtered out one of these wavelengths now the stimulations are going to change.
Now we're going to be able distinguish between this one is going to be sort of cut out so it's going to be reduced and this one over here
where the overlap occurred isn't, so what's going to result is we're going to be able to distinguish these two colors now.
It doesn't mean we're going to see them as red and green when we put the glasses on, it means that
now we can distinguish two colors that we previously couldn't. So it used to look the same to us and now they look slightly different.
That's what these EnChroma glasses are essentially doing.
OK final thing is some demonstrations of
what colorblindness feels like. This is a site I'll post in the video description. So you can look at a picture here and then you can simulate
different types of of anomalies or anopias. So you can go in and see ok, the red-weak, the protanomaly,
is going to look something like this, the green weak, deuteranomaly, is going to look something like this.
Blue weak, you can go through and try this and you can also upload your own file
and then see what would this look to someone with these different types of colorblindness. Remember in the case of the anomalies
especially, it's a shifting so it's not going to be shifted exactly the same way for everyone. So this isn't a perfect demonstration if you have a
friend who's colorblind it doesn't mean you're seeing exactly what they see but it gives you a better idea of what they experience.
OK so that's colorblindness. I hope you found this helpful, if so please like the video and subscribe to the channel for more.
Thanks for watching!