Well, duh! They had to conduct a whole scientific study to figure this one out?
Mine not only understand the concept of fairness, they've learned to not mind having to take turns on certain things! The two Bostons are crated during the day and both are anxious to get out as soon as I get home. I've learned that I couldn't take them both out on leashes at the same time - I just CAN'T unless I want both shoulders dislocated and to be dragged down the porch steps. So they take turns on who gets out first. One week Ragan gets Mon-Wed-Fri and Katy gets Tues-Thurs. The next week we reverse. And I actually worry that I'm accidentally slighting one of them! When I come in the door I tell them whose turn it is and the other one waits patiently for their turn. If Katy gets out first and Ragan cries to get out, Katy will run in and sit in her crate, waiting for me to close the door, so her sister can have her turn! When it comes to other things though, it has to be even. If one gets a bite of something, the other two have to get the same. If they don't, their feelings are obviously hurt. Bostons have such rubbery little faces, you don't ever have to wonder what they're thinking. They can get just about every expression on their face that a person does!
I've noticed the 'two week' thing too! I don't think they really forget, they just adjust and get on with it. My first Boston, Rudy, was eleven when I got Ragan as a tiny puppy. Rudy died at thirteen when Ragan was two. For just about two weeks Ragan looked for Rudy everywhere, then she finally just stopped looking. They have a pretty good long-term memory too! My oldest one, Rudy, grew up with my kids. My daughter moved out of state and when she came here to visit the first time she hadn't seen Rudy in almost five years. Rudy knew who she was immediately and was overjoyed to see her. She jumped right in her lap and covered her with kisses.