Fourth dimension of colour

[chickenfan]

It seems someone at Exeter University is researching what different species see, and it turns out chickens have exceptional eyesight, better than bees and way better than ours, and that whereas we see in a three colour spectrum (red,green, blue), chickens have a fourth spectrum and see in a huge range of colours.

 

[chrismahon]

Very interesting Chickenfan. I know their eyesight is exceptional but can't understand why they react to certain colours more than others. So a blue bucket replaced by a purple one causes panic, but a purple one replaced by a pink one does not? Perhaps there are more colours in the buckets than we can see -this 4th spectrum perhaps?

 

[rick]

It's Ultra Violet Chris and blue is at that end of the spectrum. But also something that you can't see is the effect of, for example, a UV reflective, maybe waterproof, coating on an item. So two green (I.e.) jumpers might look completely different to them, especially if one is wool and one polyester.
I find it fascinating because it's like the question 'how do I know that the colour we both describe as blue looks the same to you?' We sometimes 'see' UV light as a fluorescence on some materials - the energy is absorbed and re-radiated at a lower frequency. But that's not seeing UV light. Chickens (and many birds) can see it directly. The colour they perceive doesn't have a name in human language!
Referring to it as an extra dimension is also very thought provoking:
Red, Green, Blue, Bok
Red + Green = Orange
Red + Bok = ?????

 

[chickenfan]

Humans see in red, yellow and blue. Dogs, sheep and cattle see in blue and yellow, but in a much more muted colour range than us even within the blue and yellow. Interestingly cattle don't see red at all, so no worries about passing a bull wearing red. Vision is key to bees so they see in ultraviolet and in a colour contrast that we are blind to. So a bee will see a dandelion as a whole series of pinks and purples. Chickens, on the other hand, are Tetrapromats (spelling?) which means that they have the best of human vision and the ultra-violet bee vision combined. This was all on Countryfile last night with a Sensory Ecologist who is an expert in animal vision from Exeter University.

I'm always amazed that my birds seem to follow exactly what I'm doing in the house too, so perhaps the ultra-violet and increased contrast range gives them an ability to look into a dark building too.

 

[rick]

I'm always amazed that my birds seem to follow exactly what I'm doing in the house too, so perhaps the ultra-violet and increased contrast range gives them an ability to look into a dark building too.

I know Chickenfan. I creep down in the morning to make tea and avoid the breakfast squarks but they usually spot me halfway through the house.
One paper I read talked about the shape of the eye (flattened in comparison to ours) which results in, bizarrely, short sightedness to within 2 feet which they make up for in high resolution (I know it sounds like a contradiction) and a fast frame rate so that they can see the smallest movement in the field.
I guess the smallest movement in the house in the morning means cabbage is coming!
... The more I think about it the more it makes sense - 2 square meters, roughly the space required for a subordinate chicken to be anonymous.