The predatory criminal does all he can to make that arms race look like détente. “He was so nice” is a comment I often hear from people describing the man who, moments or months after his niceness, attacked them. We must learn and then teach our children that niceness does not equal goodness. Niceness is a decision, a strategy of social interaction; it is not a character trait. People seeking to control others almost always present the image of a nice person in the beginning. Like rapport-building, charm and the deceptive smile, unsolicited niceness often has a discoverable motive.

People who want to deceive you, I explain to Kelly, will often use a simple technique which has a simple name: too many details. The man’s use of the story about the cat he left unfed in a friend’s apartment: too many details. His reference to leaving the door open, “like ladies do in old movies”: too many details. His volunteering that he is always late (“broken watch, not my fault”): too many details.

When people are telling the truth, they don’t feel doubted, so they don’t feel the need for additional support in the form of details. When people lie, however, even if what they say sounds credible to you, it doesn’t sound credible to them, so they keep talking.