How do we determine other another animal’s vision?

Question

…Like knowing that a snake can see infrared light, or a cow sees shades of red, or a fly sees in slow motion among others?

In: 10

Answer 1

You’re slightly conflating the experience of vision with the mechanics of light sensing here. There is a difference between things we can measure (i.e. that snake photoreceptors might be sensitive to infrared light, or that cow photoreceptors might only be sensitive to red light) and things that are subjective (what it feels like to be a cow looking at the world).

For the first, we can take different samples of cells from animals and examine them, and also examine their response to stimuli. For instance you could take cow eyes and expose them to different spectra of light and see whether there’s a reaction in the cell that indicates it’s been activated. This is a quantitative examination, in that you can translate the tests into data that anyone else can try to reproduce and agree on.

However, when you say a fly sees in “slow motion” or a cow sees in “shades of red”, there’s an ambiguity of whether you mean, for example, that to a cow the world looks like it would to us if we wore red tinted glasses all the time or that to a fly humans look like they’re moving at 1/10th normal speed. These are questions about “[qualia](https://en.wikipedia.org/wiki/Qualia)”, the subjective experience of a creature. A common example of a qualia question is “Does another person see the same color as I do when we both look at a _red_ object?”. You can both agree that it’s red, that it’s similar in color to other objects that are red, but there’s literally no way to know that what you see as red, the other person perceives as what you think of as green, and vice versa.

So, in summary, we can physically examine the means that a snake or a cow or a fly uses to perceive the world, and measure that snakes can respond to infrared light, cows to only shades of red light or that flies can respond to stimuli faster than humans, but we can’t say for certain what the internal experience of those creatures is like.