  Animals execute goal-directed behaviours despite the limited range and scope
of their sensors. To cope, they explore environments and store memories
maintaining estimates of important information that is not presently available.
Recently, progress has been made with artificial intelligence (AI) agents that
learn to perform tasks from sensory input, even at a human level, by merging
reinforcement learning (RL) algorithms with deep neural networks, and the
excitement surrounding these results has led to the pursuit of related ideas as
explanations of non-human animal learning. However, we demonstrate that
contemporary RL algorithms struggle to solve simple tasks when enough
information is concealed from the sensors of the agent, a property called
"partial observability". An obvious requirement for handling partially observed
tasks is access to extensive memory, but we show memory is not enough; it is
critical that the right information be stored in the right format. We develop a
model, the Memory, RL, and Inference Network (MERLIN), in which memory
formation is guided by a process of predictive modeling. MERLIN facilitates the
solution of tasks in 3D virtual reality environments for which partial
observability is severe and memories must be maintained over long durations.
Our model demonstrates a single learning agent architecture that can solve
canonical behavioural tasks in psychology and neurobiology without strong
simplifying assumptions about the dimensionality of sensory input or the
duration of experiences.
