  Action advising is a knowledge transfer technique for reinforcement learning
based on the teacher-student paradigm. An expert teacher provides advice to a
student during training in order to improve the student's sample efficiency and
policy performance. Such advice is commonly given in the form of state-action
pairs. However, it makes it difficult for the student to reason with and apply
to novel states. We introduce Explainable Action Advising, in which the teacher
provides action advice as well as associated explanations indicating why the
action was chosen. This allows the student to self-reflect on what it has
learned, enabling advice generalization and leading to improved sample
efficiency and learning performance - even in environments where the teacher is
sub-optimal. We empirically show that our framework is effective in both
single-agent and multi-agent scenarios, yielding improved policy returns and
convergence rates when compared to state-of-the-art methods
