Eli5: How do scientists determine the vision of a specific animal?
In: Biology
The biggest way is just to observe what they do and do not react to. You can do this in the wild and experimentally in the lab to narrow things down even further. For instance, we can observe that a lot of flowers have ultra violet markings that we cannot see. And we can observe that these markings do seem to have an effect on insects and which flowers they choose to visit. So we can then confirm this by making similar ultraviolet markings on things that are not flowers in the lab and see whether or not that also attracts the same insects. If the behavior continues it is reasonable to conclude that it is because the insects are seeing the ultraviolet light. If they do not react to it then it might have been something else like smell that was driving them. And after that either way we do more tests to get more data and make more accurate conclusions.
Often, the animals are trained to identify a color or object, rewarded for doing so, and then presented with a variety of colors and objects to see if they can distinguish between them. There was a short video floating around Reddit for a while of a chicken that had been taught to peck at a red circle to get a treat. Then, researchers mix up circles of a bunch of different colors and see if the chicken can find the red one. If the chicken consistently pecks at a different color – say, green – then it probably indicates that the chicken is unable to distinguish between those colors.
Similarly, you could train an animal to come to a target and then move a long distance away from the animal. If they can still identify the target and move towards it from that distance, it means their vision can still clearly see from that distance.
Dissecting the eyes and inspecting them also goes a long way today, since we have a plethora of tools to inspect organs and cells. Scientists can cut a section of a retina and then use a microscope to literally count the cones and rods to check their density. They can take individual cells and shine light with a specific wavelength on the cells to see if they react. Scientists can even look at the genes to find similar genes to what we know codes for certain proteins in our eyes or another, well-studied animal’s eyes, which we know are sensitive to a particular wavelength of light.
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