Rats Love Hide-and-Seek

Science can be fun!:

Why did the rats play along? It’s possible that they were going after tickles and other social rewards. After all, for two decades researchers have known that rats enjoy being tickled and react by producing ultrasonic chirps that can be compared to laughter. But Reinhold found that once discovered, the rats would often run away and re-hide, delaying their reward and prolonging the game itself. “It seemed really playful,” she says.

She and her colleagues believe that rather than pursuing rewards, the rats were playing for the sake of it. They played because they had fun. For a start, and this is an unusual but welcome line to see in a scientific paper, “the animals looked like they are having fun,” the team writes. When they reunited with Reinhold, they frantically jumped on the spot—a behavior delightfully known as freudensprung, or “joy jumps.” They also teased Reinhold by repeatedly getting close and running away.