To find out more about the rat in the can effect, you can read this book: The Tangled Wing: Biological Constraints on the Human Spirit by Mel Konner, where I think it is described. Here, I will summarize it, in simplified form. If you seriously need to know about this in more detail, do more research and don’t rely entirely on what I say here.
Once upon a time there was a psychology research lab looking into stress. They did this experiment:
Get two distinct samples of rats, as identical as they can be, in every way but one. For one group, do nothing special. For the other group, have an undergraduate volunteer arrive daily and spend a fixed amount of time cuddling with the rat, saying nice things to it, petting it, etc.
At intervals before, during, and after this period, give the rats a standard test like you do. This test involves placing the rat by itself on a floor bound by four steep walls. the floor is divided into many tiles, each just a few inches across. At regular intervals, record which square the rat is in. Over time, one can draw as sort of map showing where the rat spent most of its time.
Non-cuddled rats were found to do what rats usually do in this test. They spend more of their time around the edges of the floor, near the walls. This is what rats do, spending their time moving along walls and in shadows out of fear.
The cuddled rats, on the other hand, spent their time more or less randomly across the floor, and were also observed to spend more time looking up and around on their hind limbs.
Interpretation: If you give rats loving care they become well adjusted human toddlers. Therefore, if you give human toddlers loving care, they also become well adjusted human toddlers.
Some time later, a different research group, or maybe the same research group after a few beers, became suspicious of those findings, and decided to have another look at rats.
They performed the same exact experiment, but with one change. Instead of an undergraduate volunteer showing up daily to cuddle half the rats, the volunteer simply picked the rat out of the cage, placed it in an empty coffee can, put the lid on the can, and shook the can around a bit. Not enough to harm the rat, but enough to freak it out.
After the same time had passed with this treatment, the rats were tested in the same way.
The rat-in-the-can rats, the ones shaken around like Folgers, had the same change as the cuddled rats, showing little stress or fear, not hugging the walls as rats normally do, and being curious and looking around more than normal.
Interpretation: Being picked up by an undergraduate, held in the hands, touched with the other hand, made noise at, maybe occasionally brought near the mouth for a kiss, is a rat’s worst nightmare. The giant predator has come out of nowhere, captured you, and is certainly going to eat, crush, or otherwise abuse you. Every day For days. Or, being picked up and shaken in a can every day, day after day, is in the end very very stressful.
Either way, the rat becomes over-acclimatized to stress, and beings to exhibit the utterly abnormal behavior of not avoiding further attacks by predators.
Meta-conclusion: Although endocrine systems in humans and rats are very similar and behave in similar ways, rats and humans are not very similar and at the level of the whole organism, do not behave in similar ways.