We’re not sure if this qualifies with the ongoing “Can ‘x’ play Doom?” meme, but technically it should. Per a post on Medium, Neuroengineer Viktor Tóth has not only named three rats after the brains at id Software, John Romero, John Carmack and Tom Hall, but has trained the rats to play the classic first-person shooter. Sort of.
While the rats aren’t speedrunning through E1M1 just yet, according to Tóth, he built a VR setup for the rats from scratch, and trained three of them “in an automated fashion, without manual intervention, to traverse a corridor rendered in the Doom II engine.” Tóth explains that he also tried to implement the mechanisms to further train rats to shoot in-game enemies, but “lacked the time to actually reinforce the behavior.”
In a glorified trackball setup, the rats are placed in a harness on top of a polystyrene ball, which as the rats walk on it, Doomguy moves forward. The setup uses positive reinforcement training, where the rats are given sugar water for doing the “correct” thing in the game. Namely, walking forward. The setup uses a custom Doom II map that’s essentially a long corridor with a few doors and an Imp at the end.
One of the neat parts of the article is Tóth explaining the rats’ limitations in visual acuity when compared to humans. Rats view the world with red-green colorblindness, and have poorer color vision than humans. Therefore, Tóth had to do a bit of tweaking with the game’s graphics and sound to maximize their potential in training.
One of Tóth’s goals in the experiment was to automate portions of the training, but also to teach the rats how and when to shoot via a rearing movement with the harness. Of course, the rats need to be taught how and when to use it.
“Simply put,” explains Tóth, “the training procedure would go as follows: the rat walks into a monster → the software detects that the monster is in the proximity of the player (and for now, let’s assume that the player is facing it) → initially the rat has no idea what to do in this situation, so the training software activates the push-pull solenoid lifting the animal slightly upwards → the head of the actuator then touches the button → monster gets shot down → reward in the form of sugary water is released to reinforce the behavior.”
Whether or not this has scientific merit is up for debate, but let’s be honest: the thought of rats playing Doom is just plain awesome.