Sunday, 25 March 2007

For your eyes only.

These are Belle's eyes. Pure Border Collie eyes.

Although we are unable to ask our dog to read an eye chart, it is possible to make some educated assumptions about their vision. The position of the eyes placed on the sides of the head determines the degree of peripheral vision and results in a visual field of 240 degrees compared with the human field of 200 degrees, for instance. Most humans have the ability to see all the different colours of the electromagnetic spectrum, and consequently perceive all its' colours. Animals, such as the dog, are often thought of as being at a disadvantage by not being able to see all the hues of the spectrum. Evolutionarily however, the dog and the human each developed the visual system that worked best for them. Humans have depended on their diurnal ability and a sense of colour throughout time to help them find food. Dogs on the other hand, were not originally diurnal animals, until humans domesticated them. Consequently, the ability to see at night was originally more important to the dog than colour. After all, their prey is often camouflaged with the surroundings, so they are unable to rely on colour vision cues as heavily as humans do to find food. Dogs have developed the ability to see in dimmer light and to detect motion that aids in their survival. Humans on the other hand, are visual creatures that heavily depend on both colour and acuity to go about their everyday lives. It is commonly believed that dogs only see in black and white. Recent evidence shows, however, that they have some degree of useful colour vision. Behavioural tests suggests that they can distinguish red and bleu but green and red appear similar to them. Dogs therefore rely on contrast and movement to identify objects.


Murph said...

I think Belle may be a cousin of mine, Eurodog. She does look rather enchanting I must say.
Thanks for the picture!

I, like the view said...

presumably dogs rely on smell, which must make up for some of the visual differences between us (between dogs and humans, I mean)

Anonymous said...

You are quite right - I can see in colour, and I prefer sleeping through most of the day. Bet you don't know what breed I am.

Jean said...

My dog's favourite toy is a red ball (Kong). So he can see his toy, but if he can't make a difference between red and green, how can he see it in the grass? I guess he can see the movement of his toy, and if it doesn't move, perhaps he can find it back using his smell?
So if I use a blue Kong, will he be able to see his toy in the grass? Would be worth giving it a try. However, I must admit that for me it's easier to find a red object in the grass than a blue one! But this confirms your theory.

What do you think?

mutterings and meanderings said...

Border collies, like labs, have such soulful eyes.