It shouldn’t be surprising how much your writing tells about your personality. Yet, it is pretty exciting to discover what an artificial intelligence software can tell about yourself. Simply submit a blog post, a page or two from your book or other writing to a computer program and wait for an answer. IBM Watson provides a free online service where you can run a personality test for yourself or for your favorite author.

The IBM Watson Personality Insights must have 100 words at minimum in order to analyze someone’s personality. The computer algorithm makes a better job if it has more text to work with.

In order to try out how Watson works, we submitted book extracts to the service that included about thousand words each. Then, we asked Watson to review blog posts about 250 words in length from the same author. The results were slightly different between book extracts and blog posts.

It could be that the writing in a book has gone through several phases and several edits (and perhaps editors), whereas a blog post typically is drafted pretty quickly and published without help from other people.

Nonetheless, Watson gave clues which characteristics are strong in a text and which are missing.

You don’t have to enter text from Harry Potter into the IBM Watson to analyze J.K. Rowling’s personality, because Quartz already did it. In addition to Rowling, Watson assessed other popular authors, like Hemingway, E.L. James, Thomas Piketty, Harper Lee and Arthur Conan Doyle.

IBM describes its computer algorithm as follows: “The IBM Watson Personality Insights service uses linguistic analytics to extract a spectrum of cognitive and social characteristics from the text data that a person generates through blogs, tweets, forum posts, and more.”

The Personality Analysis service doesn’t request any personal information, Twitter-name or blog address. The algorithm only examines the text you submit to the online form.