Rudolf Flesch's Human Interest Formula

In The Art of Readable Writing (1949), Rudolf Flesch published his Human Interest formula along with his Reading Ease formula.

You can calculate Human Interest with this formula:

Human Interest = 3.635 pw + .314 ps

Where: pw = percentages of personal words, which include:

1. Pronouns that are not neuter such as its, they, their;
2. All words that denote gender, such as actress, Jim, father;
3. The two words people and folks.

ps= percentage of personal sentences, which include:

1. Sentences with quoted dialog.
2. Questions, commands, and requests that address the reader.
3. Exclamations;
4. Incomplete sentences, the full meaning of which is inferred.

If a sentence qualifies for more than one of these, count it only once.

Flesch scored the human interest of publications this way:

0 to 10 --dull--Scientific
10 to 20 --mildly interesting--Trade
20 to 40 --Interesting--Digests
40 to 60 -- Highly Interesting --New Yorker
60 to 100--Dramatic--Fiction