Sunday, November 17, 2013 2:08:00 PM
What's more speculative is how their brains process that incoming data. The data gathering abilities can be known for sure, but the processing much less so. That can only be partially uncovered by observation. For example, people have spents many hours watching dogs to see how they react to things of different colours, because knowing what colours a dog`s eyes can detect doesn`t necessarily tell you what colours a dog`s brain pays any attention to. Although, unsurprisingly, it turns out that on the whole animals seem to use all the data their senses gather. In the wild, anything that gives an animal any kind of edge is generally used. So, for example, birds do use ultraviolet when looking for food and snakes do use infrared when looking for food (although it`s not actually sight as such - snakes don`t detect infrared with their eyes).
Sunday, November 17, 2013 2:02:55 PM
How can scientists possibly know for sure?
For example, if an animal's eyes don`t have receptors that react to EM radiation in the wavelength range that we call ultraviolet, that animal will not be able to see ultraviolet. If an animal has only two types of cones in their eyes (like most mammals), then they will be unable to accurately perceive wavelengths in some parts of the spectrum in which they can see, i.e. they will be "colour blind".
So it is possible to tell for certain things such as what wavelengths an animal can see, how accurately they can see various colours, how vividly they can see colours, how finely they can focus, whether their eyes move independently, etc.
Sunday, November 17, 2013 10:33:19 AM
@drawman61: "How can scientists possibly know for sure?"
Scientists can mesure not only the number of different rods and cones in an eye but also the frequencies of light that create a stimulus in each type of rod and cone.
Yet, if you're talking about how can they know the qualia of vision, than the answer is they don`t. Two people can have different qualia of vision, one may see the sky and all other blue things as how you see orange but they may understand the name of the color as blue. Thats possibly an extreme example, yet we have found that different people perceive colors differently. The Himba tribe in Africa has a very hard time seeing different shades of the color blue, unlike Europeans who can see it much more vividly. Yet the Himba can see more shades of greens than Europeans. There are other differences like, they are better at seeing yellow contrasted with white than most Europeans.