The postgrad is trying to do a study of rat behavior - training it to push a lever for food or something. As a postgrad if your research ends up being bullshit you're in a pretty bad situation so every time the rat pushes it he sighs in relief because he has something to work with. The rat thinks he's the one conducting the experiment.

I don't know whether it's a good thing I got such a concoluted joke but this made me giggle.

convoluted*

I ain't callin' you for dinner!

Samefags

Internet fight!