Just to add on to this, a proper cage sized for 2 rats is probably going to take up at least a small kitchen table's worth of space. When have you ever seen a

Just to add on to this, a proper cage sized for 2 rats is probably going to take up at least a small kitchen table's worth of space. When have you ever seen a cage that size in a research lab? Besides, groups of 2 are the barest minimum you want for keeping rats. As to the whole "studying stressed out rodents might not give representative results" point, I'm reminded of the Rat Park experiment [0]. --- [0]: https://en.wikipedia.org/wiki/Rat_Park https://en.wikipedia.org/wiki/Rat_Park