Complicatedly Colourful: Vision Science

The picture I’ve put up is one of a mouse retina. The green dots are cells that have been stained with a fluorescent dye. I’m showing you this partly to show you how many cells there are in a retina (only some of the cells are stained, and humans have even more than mice). It’s also partly to complain about how I’ve been given the honourable job of having to COUNT every single one.

Anyway this is a continuation from the previous post. I finished off by talking about how we transfer what we see from the eye to the brain. Now I want to talk a little bit about what the brain sees.

The honest answer is a lot.

When you get to the brain you find cells that don’t just see a small point in space, you find cells that see different colours in that space, cells that see things pointing in specific directions and some cells that see things moving in specific directions. That is probably a very basic breakdown of the different types of things you see when separated into broad categories.

I’m going to make a small mention about the direction type cells in one of my next posts as you can do some weird things with them. But for now I’m going to concentrate on the colour ones as it might be a bit more relateable!

S = Blue, M = Green, L = Red

These are the three scientific primary colours, Blue, Green and Red. You might know them from TV input cables called ‘RGB’. For some reason artists consider the three primary colours to be blue, yellow and red. I don’t know why, can someone please tell me why?

So why are scientists right? It’s simply because we have only three types of cells that detect colour. One detects red, one detects green and one detects blue. These cells are represented by the white lines in the picture above. Together they are known as cone cells. Mix those three colours together and you get all of the colours you could ever imagine. See here for more thoughts on this.

It is more or less the same throughout the visual system. You have a group of cells that are specific for certain things (e.g. certain directions) and what you actually see is a mix of these working together. For example if you had a cell that only saw stuff moving left, and one that saw stuff moving upwards. If both of them were active you would assume you would assume you were seeing something moving diagonally. But if you looked at a specific cell you would realise they are really limited.

In fact some people are much more limited than others. In fact we are pretty limited in general. These are generally all of the colours that most humans can see:

However many humans can’t see all of those and are in fact partly colour blind. So below is what a dog can see (famous for being colour blind). It’s one for dogs as the picture was easier to find, no insult intended!:

The reasons why dogs can’t see as many colours is because they only have two cells that see different colours. It can be the same case in humans, but more commonly it is because they have two cells that see colours very close to each other. Imagine M and L lines in the picture above to be much closer to each other. There would barely be a difference!

There are also some people who have ‘monochromatic colour blindness’. This means that they can only ever see one colour. Imagine a world that is perpetually coloured in shades of red. It would probably look a bit like the film Sin City. But that is what they are stuck with.

On the other end of the spectrum there are animals such as the one below that can see in over 12 different primary colours. Imagine how vibrant that must be!

It's about *stretch arms* this vibrant!

The concluding point of this post is that we have huge amounts of cells in our retina. By the time these cells reach the brain, they aren’t just seeing spots of light, they are analysing the colour of things, the direction they are moving in and even their orientation. It’s a huge amount of information to take in. So one of the next posts is going to be dedicated to how the brain copes with this amount of information, giving us things like optical illusions.

Leave a comment


  1. The Traditional model of red blue yellow was proposed when the only means of manipulating color was paint, and these three color where the purest colors the could isolate and when mixing formed the rest much like a printer, this is caled substractive primary colors,

    in exchange with RGB primary colors, the rest of colors come from the addition of them because of the overlapping properties of light.

    by the way, awesome blog you have here, thank you so much for sharing this

    • Thanks!

      Awesome reply, makes a lot of sense as well. Probably should have thought of it myself.

      Essentially, art was before science. Which it was by a long way.

  2. sunsetwonder

     /  14/05/2012

    It is truly awesome how the eyes and the brain work together to enable us to see. In order to see, all the parts of the eyes have to function properly at the same time, so I find it very difficult to believe the eyes (and the brain) evolved into perfection by coincidences by themselves. I find it makes much more sense to believe an all intelligent God and He created everything.

    • I’ve heard that argument a lot. I even remember being taught in school that it was more likely that a gust if wind would make a jumbo jet from a junkyard (before we were taught evolution, educational bias? I think so) then the eye constructed ‘randomly’ (it’s not all that random, it’s ‘natural selection’).

      the problem I see is that peoples ideas of how they evolved is wrong. It wasn’t sudden, it took a very long time (billions of years, I refer you to my previous post: The process involved steadily putting the systems together bit by bit, and contrary to popular belief they are far from perfect. There are entire books on the subject of how we could have evolved better.

      Just think, if you had a billion piece puzzle, and you put the pieces together at random, trial an error if you were given several billion years you would at some point (statistically) put the puzzle together correctly. It would probably be a lot sooner as well. If there were room for error (which there is), it would be even faster.

      Turning that around you could ask why, if God created us, did he do so imperfectly, and if we of his image, is he imperfect? Of course this relies on the assumption that we are imperfect.

      If you want concurrent and extensive arguments for evolution I recommend:

      In general though evolution is not really questioned in science any more due to the huge amount of evidence behind it. I assure you, for any example someone uses against evolution, there will be a scientific explanation somewhere else.

      Simple Google for evolution of the eye:

      with all the references at the bottom.

      Hope this helps!

      • sunsetwonder

         /  14/05/2012

        I can’t conceive time is the answer. Could a computer or a rocket come into being from nothing, evolved from trials and errors by themselves over billions of years ? Where did life come from ? We can make and program robots but we can’t give them life.
        I had studied evolution in school too, I became a Christian because I realized a Creator God is the logical explanation for all creations, evolution is just a theory and with problems, eg. fossils of part dinosaurs part birds still not found.
        God created us with an eternal soul, this soul will go to either heaven or hell after this life. People who died unsaved without Christ will be in hell for eternity for their own sin. It is out of love and concern that I share my faith, the intention is not to argue.

  3. OK, and I respect your opinion. One of the main philosophies I’m following on this blog is that everyone has a right to disagree and/or agree. Science should never reject any theory or option, it should only test and gain evidence for each side.

    That said the intention of this blog is to firstly educate what Science has found so far (and it has not found any evidence for a creator, but plenty for evolution). The second is to incite debate on a subject. So if you want to discuss creationism vs. evolution, then your comment is welcome. If you want to make the topic controversial, but then refuse to move past an initial point on the basis of saving our souls, it is not. It’s a nice thing that you think you are doing, so your thoughts are appreciated. But if I was a firm believer in a different religion, or even a different sect of christianity (I won’t discuss my faith as it is irrelevant to the blog) your attempt would be worthless and I would consider it more to the point to try and convert you.

    Religious conversion is paradoxical when everyone thinks they are right (and I’m not saying anyone is wrong). But there is no hard evidence for any debate, whereas Science at least gives evidence. If anyone doubts a scientific theory for religious reasons, rather than using religious reasons to counteract Science, you would be taken more seriously if you studied the Science thoroughly and came up with evidence against the theory (N.B. evidence against is not the same as evidence that has not yet been found), Science may change its mind. But the overwhelming amount of study in the field has never shown the theory to be absolutely wrong, nor has it ever given any evidence for a creator (i.e. occurences that go against evolutionary theory).

    I’ve mentioned this to others before, a theory in Science does not mean a simple train of thought with no evidence. It is an idea that is thoroughly tested and refined until it is a near concrete law.

    All that said if you want to further the debate on evolution I’d suggest you take your comments to the post’s I’ve done on evolution (I gave you some links). In response to what you gave against: A computer/rocket is not a self-replicating living organism. So no it will not be created on it’s own. However life is self-replicating, and with a genetic basis has the potential to evolve (and inevitably will evolve). Where life came from has nothing to do with evolution. Evolutionary biology is the study of what happened to life once it arrived. (Although big steps in the field of Biology are being made towards understanding the origin of life). And the debate on what life is from a neuroscientific basis suggests that robots and circuit based computers could be given the same level of awareness as us (by mimicking the brains network). However the level of detail and finesse required for this to happen, as well as the complete understanding necessary, is not available to us at this time.

    As for your example. That’s not true, their have been several examples of fossils found representing an animal that shows characteristics of both a dinosaur and a bird (the growth of feathers and wing like structures). In fact a lot of palaeontologists believe most, if not all, dinosaurs had some form of feathers (again a simple google:

    Evolution is a theory with few problems, more or less every prediction made from the theory has been shown to be true. the only issues are a few controversial topics about what certain aspects of evolution do, however this doesn’t disprove the theory. I seriously suggest that you take a look at evolution from an evolutionists point of view. Get to know the evidence and then make a decision. So far all of the examples you have given as to why it is wrong are untrue and have instead been thoroughly explored and are staple arguments for evolution

  1. Complicatedly Colourful: Vision Science | Psychology and Brain News |
  2. Believing is Not Seeing: Visual Science and Reality part 1 | Science Defined

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