Deep reinforcement learning in a spatial navigation task: Multiple contexts and their representation

Deep learning has recently been combined with Qlearning (Mnih et al., 2015) to enable learning difficult tasks such as playing video games based only on visual input. Stable learning in the in the deep Q network (DQN) is facilitated by the use of memory replay, which means that previous experiences are stored and sampled from during an offline learning period. We evaluate the DQN’s ability to learn and retain multiple variations of a spatial navigation task in a virtual environment. Task variations are presented in visually distinct contexts by varying light conditions and environmental textures. Replay memory capacity is varied to measure its effect on task retention. The representations of multiple contexts learned by the DQN agents are analyzed and compared. We show that DQN agents learn a preference for common actions early on, irrespective of replay memory capacity. A limited replay memory causes agents to confuse state-values. Furthermore, we find that contexts are quickly forgotten as soon as corresponding experiences are no longer available in the replay memory.