Skimming and scanning: two distinct skills

Two operations people always confuse

Skimming. Going through a text to extract the general idea and the structure. You are not looking for anything specific, you want to know what it is about.

Scanning. Going through a text to find one precise piece of information. You know exactly what you are looking for, and you ignore everything else.

They are two different actions, with different techniques. Neither of them is reading.

Skimming

What you read. The first and last sentence of each paragraph, because in well-written English prose the first sentence carries the idea and the last one concludes or hands over. All headings and subheadings. Words in bold or italic, boxes. The first and last paragraph of each section, in full. Numbers, proper nouns, dates, which the eye catches naturally.

English is the best language in the world to skim, and that is not a compliment to English. The topic-sentence convention is taught in every American composition class and enforced by every style guide, so the point of a paragraph sits in its first sentence far more reliably than it does in French or German prose. Add the signposting vocabulary — however, therefore, in contrast, crucially, the key point is — and a well-edited English article tells you where its argument turns before you read the turn.

What you ignore. Examples, anecdotes, illustrative quotations, digressions, repetitions.