"Accidental" information leakage.The trick is designed for a person with "incontinence" of information. The more you burden him with the words "I'm sure you won't tell anyone," "You're the only one I can trust with this secret," the more he wants to share it.
At the same time, it should be understood that if you want the information to reach a specific recipient, it is necessary to tell the opponent something like, "Can I count on you that Igor will not find out anything?"
This technique is only used against extroverts, people who are "talkers. It is unlikely that it can be used against introverts, because they may want to share information, but their habit of silence will most likely prevent them from completing what they have begun.
