This is a fantastic principle to know. You need nothing. Just your brain and some easy acting skills. You can improvise anytime anywhere. It is hands off, practical and the method is very simple. And most importantly, it is fun for the participants, for yourself and for the audience. What else do you want?

You will be able to detect liars in a group of people and identify which one has selected a specific card or ESP symbol for instance. You can show your psychometry skills with borrowed objects. There are tons of applications.

You just ask the same question to some of them.

It does not use traditional fishing or anagrams, no stooges (instant or not), no preshow, no forces…