In plain words: The system automatically rescales the score it predicts, so learning stays stable even when that score's size swings wildly as the agent's behavior changes. In Atari games it removed the usual trick of squeezing rewards into a fixed range, with no drop in performance.
Abstract
Most learning algorithms are not invariant to the scale of the function that is being approximated. We propose to adaptively normalize the targets used in learning. This is useful in value-based reinforcement learning, where the magnitude of appropriate value approximations can change over time when we update the policy of behavior. Our main motivation is prior work on learning to play Atari games, where the rewards were all clipped to a predetermined range. This clipping facilitates learning across many different games with a single learning algorithm, but a clipped reward function can result in qualitatively different behavior. Using the adaptive normalization we can remove this domain-specific heuristic without diminishing overall performance.
Hado van Hasselt, Arthur Guez, Matteo Hessel, Volodymyr Mnih, David Silver
arXiv:1602.07714 · cs.LG, cs.AI, cs.NE, stat.ML · submitted Feb 24, 2016 · updated Aug 16, 2016
abstract · pdf · html · Paper accepted for publication at NIPS 2016. This version includes the appendix