What do you think of when you hear the term “lab rat”? Chances are, you might not picture an animal happily playing rough-and-tumble with a human handler and then coming back for more. Scientists have traditionally studied negative expressions in rats, as they are more reliable and easier to elicit (imagine a rat freezing still when exposed to sudden loud noise). However, a group of researchers from the Division of Animal Welfare at the University of Bern in Switzerland decided to see if they could get positive facial expressions out of lab rats instead. To do this they developed a novel “two-handed” tickling experiment and found that rats do indeed exhibit robust positive emotional indicators via pinker and more relaxed ears. Take a look at these images and see if you can identify the happier rat!