Polarization vision through a colour vision analogy I'm writing to understand how polarization vision would work through the analogy of colour vision. 
I'm reading the research paper "Functional Similarities between Polarization Vision and Colour vision" (Bernard & Wehner, 1976) and can't grasp the analogy. 
The point at which I become confused is when it discusses the sensitivity being independent of degree. From then onwards I am just confused. Can anybody please help me break this down?



 A: 
The point at which I become confused is when it discusses the sensitivity being independent of degree ...

A short and simple answer is two-fold, but please note that paper is old and there are newer findings.

*

*Polarization based vision is adapted for processing by a smaller brain. In humans the brain plays a significant role in vision processing, in invertebrates the smaller brain needs actionable information to be presented to the brain and this is believed to be done using interval decoding.
Photoreceptor sensitivities are evenly spread through the invertebrate's visible spectrum but instead of being able to distinguish between similar colors they are able to distinguish between similar polarization angles. Unpolarized light in invertebrates is somewhat analogous to white light in humans.


*Humans don't know if we are looking at even amounts of red green and blue or a more complicated spectrum which appears white, nor the polarization. With polarization based vision the ability to discriminate similar colors is poor but the ability to discriminate between similar polarization angles is excellent.
Human color vision sensitivity is not based on polarization, only frequency and amplitude. Polarization based vision is less affected by amplitude (analogous to moderatley high dynamic range and low light sensitivity), not very good at distinguishing between similar colors, and excellent at determining polarization through scanning movements; usually there is a wider spectral range of visible light.
Perhaps an easier explanation is offered in the thesis: "Colour Vision in Mantis Shrimps: Understanding One of the Most Complex
Visual Systems in the World" (.PDF) (2014), by Hanne Halkinrud Thoen. A very short quote (it's 156 pages) of some additional interesting information:
Page 21:

"We have three colour receptors (short (S), medium (M) and long (L)) in the retina and opponent cells in the LGN, which send chromatic information to the V1 and the inferior temporal cortex areas of the brain for further processing. We also know that our three receptors are sufficient to encode many colours between 400-700 nm very well and that we are able to discriminate between colours from 1-5 nm apart, at least in some areas of the spectrum (De Valois and Jacobs, 1968, Pokorny and Smith, 1970).
...
Previous studies (Marshall et al., 1996, 2007) have suggested that, instead of using an opponent processing system like that of humans, stomatopods have opted for a much simpler design, relying on parallel processing and binning of colour signals. This implies that, instead of taking the spectral output from each channel and comparing them, the information is rather being processed in parallel streams, essentially “binned” into separate compartments where colour information is sent directly and linearly from the retina to the brain. An analogue to this system could be the cochlea in the
inner ear where sound is encoded on the basis of frequency. Another possibility, which is not necessarily mutually exclusive is that the colour is encoded on the basis of serial dichromacy (Marshall et al., 1996, Cronin and Marshall, 2001). In this organisation, each midband row would function as a dichromatic colour channel, comparing the input from the distal and proximal main retinular cells. Such a system would require much less processing power than a fully opponent
organisation, and would leave each channel (row) with a narrow spectral window to analyse. Previous work on stomatopod neural wiring beneath the retina (Fig. 1.3 a) (Kleinlogel et al., 2003,
Kleinlogel and Marshall, 2005), and visual modelling (Chiao et al., 2000) gives support to the hypothesis of a simpler colour processing system.".

Page 129:

"The work presented in this thesis provides new insights into how the complex colour and polarization vision of stomatopods work. Both behaviourally and neuroanatomically stomatopods appear to use a different type of colour vision than other animals (Marshall and Arikawa, 2014), which is based on simplified sampling of colours to enable quick and reliable colour judgements. For an aggressive animals like the stomatopod (Dingle and Caldwell, 1969, Adams and Caldwell, 1990), with many types of chromatic signalling displays used in complex behavioural situations (Steger and Caldwell, 1983, Caldwell, 1992, Cheroske et al., 1999, Mazel et al., 2003), having such colour vision may be beneficial and warrant the loss of fine colour discrimination. Behavioural studies carried out by How et al. (2014a, 2014b) on the stomatopods ability to discriminate different
angles of polarised light indicate that their polarization vision may also function on similar simplified principles.".

