Shallow outline

Claim: what matters most sits at the top of a document's hierarchy, and the outline stays shallow: at most three levels of headings.

What it asks

  • The main claims are top-level: headings or the first sentence of each part. Detail sits below them.
  • Three heading levels at most. A fourth level is a sign that the part is a document of its own.
  • Headings that name their content, so the outline alone gives the gist (signal the structure).

Why

  • Idea units high in a text's content structure are recalled better than low ones, the levels effect (Meyer & McConkie 1973; Meyer 1975, secondary). Read first-hand: superordinate propositions were recalled better than subordinate ones, 86% against 74% (Kintsch 1973).
  • Readers slow down more at a changed word high in the hierarchy than low in it (Wu et al. 2016).
  • Readers who follow the top-level structure comprehend better (Meyer et al. 1980), and adults who attend to headings write the best summaries (Hyönä et al. 2002).
  • The tree of a text can be made explicit: Rhetorical Structure Theory describes it as nucleus and satellite spans (Mann & Thompson 1988).

Limits

The levels effect depends on the reader's skill (Meyer et al. 1980). The three-level limit is not measured; it follows from the effect and from browsable folders.