Even when you rationalize that the robotic rat created by researchers in Tokyo exists in the name of science, it's still a pretty cruel machine. As reported by Wired UK, scientists developed the mechanical rat to attack and intimidate living, breathing rats. It does this to stir depression in the rodents, which in turn allows experts to test antidepressants and other drugs potentially destined for human consumption. Researchers at Tokyo's Waseda University have found that assaulting the rats physically leads them to enter depression quicker than other methods; those include forced swimming and electrocution. But those tactics pale in comparison to the fear and anxiety that the robot rat can cause.

The bot operates in three separate modes: "chase" commands the robot to closely stalk real-life rats but not attack them directly, Despite the lack of physical contact, this approach still proves successful at inducing fear since the rats are constantly dreading an ambush. When the robot does strike, a "continuous attack" sees it constantly running into its target, whereas an "interactive attack" mode cuts those torment sessions into five-second intervals. Researchers find that the method proved most successful introducing depression in young rats, with "interactive" strikes proving useful as the rodents grew older. But as we mentioned at the outset, the team is hoping to use its findings for the greater good. "The experimental result suggests that the interactive attack and the continuous attack have different effects on rats. Using this methodology, it is possible to make a theory of how external stimulus induces stress in individuals. It can be a new research paradigm in psychic medicine."