Researcher lets rats play Doom

Software designer Victor Toth has spent the past year training rats to play Doom. He finally managed to get rats to maneuver the game character through a simple level.

Toth has built a ‘VR setup’ to automatically train the rats. The setup consists of a polystyrene ball that is tracked with motion sensors. Using a harness attached to a mechanical arm, the rat is then placed on that ball. The screen with the game is in front of the rat, and it is the rat’s task to guide the game character to the exit while walking on the ball. In front of the rodent is a small tube with sugary water from which it can drink if it does the ‘right’ thing.

At the start of the experiment, the ball automatically moved along two axes, forward-backward and left-right, using self-programmed motors, to encourage the rat to walk in the right direction. Because the motors exert relatively little force, the ball stops moving when the rat lies on the ball with its full weight. This didn’t force it to walk, but just encouraged it, which Toth said helped with the process. Finally he managed to get the rats to run on the ball on their own.

The minilevel was built by Toth in the Doom II engine, and was specifically intended for this experiment. It consists of only one long, straight corridor. Around a third of the way up there is an enemy who has to shoot the rat. Toth says he has also built a mechanism for this. The training software sees the player standing in front of the enemy and activates the push-pull solenoid by lifting the animal slightly. The head of the actuator then touches the button, causing the player to shoot.” By stimulating this behavior with the sugar water, Toth hopes that the rat will eventually go up to touch that button. “But I didn’t have the time to actually reinforce the behavior,” he adds.

Toth calls the 11-day experiment semi-successful. Despite trying to automate things as much as possible, he still had to be constantly there himself; for example, to put the rat on the ball and take it off. It was also not possible to let the rats shoot on their own, without the automated system helping out. In addition, the level only consists of a long, straight corridor, and despite the fact that a left-right mechanism has been built for the ball, there has been no experimentation with turns. Toth says he did not have time to spend longer with the experiment due to ‘personal reasons’.