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All of those things about visual processing are true. > You can't reduce it to three axes. This is my claim: It is possible to represent all possible visual s

by tbabb 9y ago

All of those things about visual processing are true. > You can't reduce it to three axes. This is my claim: It is possible to represent all possible visual stimulus with: f(direction, time) -> (a, b, c). That is what I mean by "vision is three dimensional". It is not possible to add another channel "d" to the (a,b,c) tuple which is not redundant; so anything you add would not be an extra axis or increase the dimensionality of the perception space. The brain/retina may generate lots of extra "channels" from processing this (moving) three-valued image, but those extra channels can't be stimulated independently of each other; they depend entirely on those original three degrees of freedom as a function of space and time. In that sense they aren't really "axes", because they aren't degrees of freedom. That's what I mean by "there isn't an extra channel." If you agree with that, then we don't disagree and we are just arguing semantics. :)

edejong 9y ago
It’s funny that you introduce time in your equation, because it shows how your view is incomplete. In our visual system, you cannot reduce to three dimensions without creating a recursive relation. It should be more like: Ret(a,b,c)_t = f(Ret(a,b,c)_{t-1}, current_stimulus) Since it is a recurrence, we cannot reduce to three dimensions.
shawnz 9y ago
Couldn't you use this same line of thinking to argue that only one dimension is required? Our eyes may generate 3 channels, but don't they depend entirely on the frequency of light received which is one dimensional?
- krallja 9y ago
  Light is not perceived at a single frequency. It is a spectrum. That’s why you can see non-spectral colors like pink.
  - shawnz 9y ago
    OK, well, are there any colours which are not representable with two frequencies? That is still less than three dimensions.
    - krallja 9y ago
      White.
      - shawnz 9y ago
        Isn't that representable with a mixture of blue and yellow light?
        tbabb 9y ago
        You can pick a blue and a yellow and a proportion at which to mix them which will produce white, but for any two primaries you pick, there are a multitude of colors you can't represent. For example, if your basis is blue-yellow as you suggest, then you can't represent red or green (and an infinity of other colors off-axis). Fundamentally the chromaticity diagram[1] is 2D (with a third axis for intensity). You need to mix at least three points to span the space of the plane. [1] https://dotcolordotcom.files.wordpress.com/2012/08/anatomy-of-a-cie-diagram2x.png https://dotcolordotcom.files.wordpress.com/2012/08/anatomy-o...
Balgair 9y ago
To be fair, the receptors are VERY time dependent too. Take a stare at the top bar for ~20 seconds and then move your eyes down just a bit. You'll see an echo image of the opposite color (colorblindness depending). This shows that even a 'little' time spent saturating the retina will effect the later images. As other people mention, the retina does a LOT of pre-processing before any 'signal' gets sent. The very first synapse from the receptor is heavily modified by horizontal and bipolar cells in a time-dependent reactive manner. The 'images' we 'see' are nothing like what the retina 'sees'. People with cataracts will commonly have very advanced occlusions before thinking there may be a problem, due to the incredible amount of processing the retina itself does. They really cannot 'see' that they cannot 'see'. So, trying to reduce vision to a color mapping is just so ... computational. Biology is not like that all the time. It's not a 'map' like with sound and hearing (where tonotopy is semi-conserved throughout brain processing). With vision, things are used as 'information' almost instantly, but for certain by the end of the LGN into V1. You can't really backtrack the data through the system once it hit V1, it self-modifies the memristance of the synapses too quickly to chase the action potentials again. So thinking of things as 'red' isn't what the brain wants to do, it's not matrix algebra. It's 'grandmother' and 'tiger' and 'that-look-in-her-eye'.

by tbabb 9y ago

edejong 9y ago

It’s funny that you introduce time in your equation, because it shows how your view is incomplete. In our visual system, you cannot reduce to three dimensions without creating a recursive relation. It should be more like: Ret(a,b,c)_t = f(Ret(a,b,c)_{t-1}, current_stimulus) Since it is a recurrence, we cannot reduce to three dimensions.

shawnz 9y ago

Couldn't you use this same line of thinking to argue that only one dimension is required? Our eyes may generate 3 channels, but don't they depend entirely on the frequency of light received which is one dimensional?

krallja 9y ago
Light is not perceived at a single frequency. It is a spectrum. That’s why you can see non-spectral colors like pink.
- shawnz 9y ago
  OK, well, are there any colours which are not representable with two frequencies? That is still less than three dimensions.
  - krallja 9y ago
    White.
    - shawnz 9y ago
      Isn't that representable with a mixture of blue and yellow light?
      - tbabb 9y ago
        You can pick a blue and a yellow and a proportion at which to mix them which will produce white, but for any two primaries you pick, there are a multitude of colors you can't represent. For example, if your basis is blue-yellow as you suggest, then you can't represent red or green (and an infinity of other colors off-axis). Fundamentally the chromaticity diagram[1] is 2D (with a third axis for intensity). You need to mix at least three points to span the space of the plane. [1] https://dotcolordotcom.files.wordpress.com/2012/08/anatomy-of-a-cie-diagram2x.png https://dotcolordotcom.files.wordpress.com/2012/08/anatomy-o...

Balgair 9y ago

To be fair, the receptors are VERY time dependent too. Take a stare at the top bar for ~20 seconds and then move your eyes down just a bit. You'll see an echo image of the opposite color (colorblindness depending). This shows that even a 'little' time spent saturating the retina will effect the later images. As other people mention, the retina does a LOT of pre-processing before any 'signal' gets sent. The very first synapse from the receptor is heavily modified by horizontal and bipolar cells in a time-dependent reactive manner. The 'images' we 'see' are nothing like what the retina 'sees'. People with cataracts will commonly have very advanced occlusions before thinking there may be a problem, due to the incredible amount of processing the retina itself does. They really cannot 'see' that they cannot 'see'. So, trying to reduce vision to a color mapping is just so ... computational. Biology is not like that all the time. It's not a 'map' like with sound and hearing (where tonotopy is semi-conserved throughout brain processing). With vision, things are used as 'information' almost instantly, but for certain by the end of the LGN into V1. You can't really backtrack the data through the system once it hit V1, it self-modifies the memristance of the synapses too quickly to chase the action potentials again. So thinking of things as 'red' isn't what the brain wants to do, it's not matrix algebra. It's 'grandmother' and 'tiger' and 'that-look-in-her-eye'.