Designing safe AI systems will require us to design algorithms that don’t attempt to do this, and will teach us to specify and shape goals in such a way they can’t be misinterpreted by our AI agents.

One of the games we’ve been training on is CoastRunners⁠(opens in a new window). The goal of the game—as understood by most humans—is to finish the boat race quickly and (preferably) ahead of other players. CoastRunners does not directly reward the player’s progression around the course, instead the player earns higher scores by hitting targets laid out along the route.

We assumed the score the player earned would reflect the informal goal of finishing the race, so we included the game in an internal benchmark designed to measure the performance of reinforcement learning systems on racing games. However, it turned out that the targets were laid out in such a way that the reinforcement learning agent could gain a high score without having to finish the course. This led to some unexpected behavior when we trained an RL agent to play the game.

The RL agent finds an isolated lagoon where it can turn in a large circle and repeatedly knock over three targets, timing its movement so as to always knock over the targets just as they repopulate. Despite repeatedly catching on fire, crashing into other boats, and going the wrong way on the track, our agent manages to achieve a higher score using this strategy than is possible by completing the course in the normal way. Our agent achieves a score on average 20 percent higher than that achieved by human players.