According to a new study, rats like to be tickled. They even make a noise that resembles laughter, except that it’s ultrasonic (so we can’t hear it).
Actually, after reading the description of the “tickling,” I think the researchers were just playing with the rats. One of the researchers says, “The animals became bonded to you and came back for more. Every possible measure of whether they like it shows yes, they love it.” That may have been news to him, but anyone who has pet rats already knows that they bond with humans and love attention. But the business about the ultrasonic chirps is interesting.