  This is an integrative review that address the question, "What makes for a
good explanation?" with reference to AI systems. Pertinent literatures are
vast. Thus, this review is necessarily selective. That said, most of the key
concepts and issues are expressed in this Report. The Report encapsulates the
history of computer science efforts to create systems that explain and instruct
(intelligent tutoring systems and expert systems). The Report expresses the
explainability issues and challenges in modern AI, and presents capsule views
of the leading psychological theories of explanation. Certain articles stand
out by virtue of their particular relevance to XAI, and their methods, results,
and key points are highlighted. It is recommended that AI/XAI researchers be
encouraged to include in their research reports fuller details on their
empirical or experimental methods, in the fashion of experimental psychology
research reports: details on Participants, Instructions, Procedures, Tasks,
Dependent Variables (operational definitions of the measures and metrics),
Independent Variables (conditions), and Control Conditions.
