Robot Technology should contribute to the progress of other research fields. We’d like to propose one example of it. In psychology, basic medicine and biological science, several experiments on animal behavior have been performed to clarify brain functions or mechanisms of learning. These experiments have been playing very important role to understand human mind. Rats and mice have been well used in these experiments. Therefore, we have been developing quadruped robots that reproduce animal behavior as new experimental tools. We developed a quadruped robot that has 4 legs and reproduces some social behaviors. Each leg has 3 DOFs. The robot also has 2 DOF at the neck and 2 DOF at the waist.