Many high-level cognitive tasks involve understanding - the mechanisms by which an agent attempts to construct accurate mental representations of its world. In this paper, we discuss two such processes: explanation and question answering. We propose four theoretical assumptions about representation and processing that arise in these tasks: both involve inference, this inference requires making default assumptions, it occurs in an incremental manner, and it produces structures that can be expressed as directed graphs of conceptual ground literals. We analyze two models of explanation and question answering in terms of these commonalities and evaluate experimental claims about them using reading comprehension passages. In closing, we discuss our findings in light of related research.