In 2021 PCG reported on a singular scientific experiment: rats named Carmack and Romero had been taught how to ‘play’ Doom. I use the inverted commas because, cute and cool as it was, the question of whether the rats were really playing Doom in any meaningful way, or just running on a ball for some delicious sugar water, was not conclusively answered.
The project leader Viktor Tóth said at the time he wasn’t happy with how they’d implemented the shooting response, and four years later the team is back with a new setup that significantly expands what the rats can do (first spotted by Tom’s Hardware). And this time, the rodents are rocking a trigger mechanism.
The limitations meant that it was a bit of a stretch to say the rats were playing Doom, but as Tóth said you could make a decent argument they were “kinda” playing Doom.
“The shooting input is a custom-built hand-operated lever,” writes Tóth. “Rats pull it with their paws to fire. The lever is held in place by small springs, encased in a 3D-printed housing. It includes a rotary encoder to detect motion and a stepper motor to actuate it.”
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Everything about the setup is external: sensors, motion tracking, visual feedback, and of course the good old rewards reinforcing correct behaviours. The initial experiment was a Tóth solo project, while this v2 was built in collaboration with electrical engineer Sándor Makra. Akos Blaschek also assisted in documenting the project for open-sourcing and, should you wish to build your own rat VR hardware, here is how to do it.
The results? “The rats successfully learned to navigate the virtual environment and trigger the shooting mechanism,” writes Tóth. “Habituation took approximately two weeks per rat. While advanced training wasn’t completed due to time constraints, initial data showed promising engagement with the system. Full behavioral validation requires longer training periods.”
So perhaps we can forget about the inverted commas, and simply say that rats can now play Doom. The rodent versions of Carmack and Romero have long since gone to the great sugar water dispenser in the sky, but the legacy is clear: they walked, so later rats could run ‘n gun.
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