DeepMind’s attempt to teach an AI to play soccer started with a virtual player writhing around on the floor—so it nailed at least one aspect of the game right from kickoff.
But pinning down the mechanics of the beautiful game—from basics like running and kicking to higher-order concepts like teamwork and tackling—proved a lot more challenging, as new research from the Alphabet-backed AI firm demonstrates. The work—published this week in the journal Science Robotics—might seem frivolous, but learning the fundamentals of soccer could one day help robots to move around our world in more natural, more human ways.
“In order to ‘solve’ soccer, you have to actually solve lots of open problems on the path to artificial general intelligence [AGI],” says Guy Lever, a research scientist at DeepMind. “There’s controlling the full humanoid body, coordination—which is really tough for AGI—and actually mastering both low-level motor control and things like long-term planning.”
An AI has to re-create everything human players do—even the things we don’t have to consciously think about, like precisely how to move each limb and muscle in order to connect with a moving ball—making hundreds of decisions a second. The timing and control required for even the most basic movements can actually be surprisingly tricky to nail down, as anyone who has ever played the browser game QWOP will remember. “We do that without thinking about it, but that’s a really hard problem for AI, and we’re not really sure exactly how humans do that,” Lever says.
DeepMind’s simulated humanoid agents were modeled on real humans, with 56 points of articulation and a constrained range of motion—meaning that they couldn’t, for instance, rotate their knee joint through impossible angles à la Zlatan Ibrahimovic. To start with, the researchers simply gave the agents a goal—run, for example, or kick a ball—and let them try and figure out how to get there through trial and error and reinforcement learning, as was done in the past when researchers taught simulated humanoids to navigate obstacle courses (with comical, quite unnatural results).