When an animal is presented with water and a bottle containing a sucrose solution, more often than not it prefers the sweet solution.

When the animal is under a lot of chronic stress, it prefers to drink pure water rather than the sucrose solution.

It is important to note that it still drinks roughly the same volume of liquid in both instances.

If an animal is trained to do this test and prefers the sucrose solution, the sucrose preference test can be an adequate way to assess if the animal is under stress.

• Because it should prefer the water if it is under stress.

In order to perform this test, one would need two bottles, water, sucrose ready for dilution, and the experimental animal.

Personally, I think this is a reasonable model to measure stress because it is not like someone could just ask the mouse how it is feeling.

I don't understand how it works, because I'm sure an animal would want water if it is under stress, but I also feel like they would want the energy from the sucrose also.

In the end, this seems like a long-accepted test, so I am sure there is at least minor validity to it.