In the mid-1990s, id Software unleashed Doom and a year later its sequel Doom 2 into the wild, creating something of a shockwave throughout the gaming world, with the first-person shooters going on to influence a whole genre. With the original FPS pioneering early online multiplayer gaming, the nearly 30-year-old title is still being played to this day, with John Romero himself still making content for the classics. While, traditionally, human beings are more prone to playing, a scientist has managed to train a number of rats to have a go at a custom-built level.
According to a report, as well as a YouTube clip, a neuroengineer named Viktor Tóth has spent the better part of a year teaching three rats to play Doom in a sort of rudimentary way. Tóth explains that they created a VR setup in which the rats could "traverse a corridor" which was built in the Doom 2 engine. Each rat was placed with a harness onto a ball attached to motion trackers. Tubes were placed between the rats and the monitor showing the level, and they were rewarded with sugary water from the tubes when they learned to do the "right" thing.
It was then a case of training them to kill one of Doom's most notorious monsters, the imp, which appeared down the long corridor. Initially, the rats were not sure what to do, but Tóth explains, hit detection in the software was initiated at first that would operate a "push-pull solenoid lifting the animal slightly upwards," touching the button that shoots the imp. With positive reinforcement, the rat gets rewarded with the sugary water once it learns what to do.
On top of this clever and interesting experiment, the rats are named after the co-founders of id Software John Romero, John Carmack, and Tom Hall, with each rat having their own personality. It's perhaps important to state that this is only a rudimentary implementation. The short video shows that the rats are indeed activating the on-screen action in a basic way, but, as the report says, it raises the question of whether they are playing in any "meaningful" way.
Overall, it's a fascinating experiment and it opens up the possibility for other ways that rodents, and maybe other animals, could be trained to "play" all sorts of video games, not just Doom. While fans are often keen to port Doom over to unusual devices, Tóth has shown that the game has had such an impact on the industry, that it can be used in the pursuit of science.