But since you probably don't have brain scans at your disposal, there are some other ways to tell if you might be dealing with a real-life psychopath.
A new study examining existing literature on psychopaths discovered that they may be detected through subtle differences in the way they hold conversations. Here are nine specific communication patterns psychopaths use:
1. They speak in the past tense.
Psychopaths use more past-tense verbs than other people. When talking about an event happening right now, most of us would say, "I think this is a good idea." A psychopath might be more likely to say, "I thought that was a good idea." Researchers suspect this is because they are detached from their behavior and their environment.
2. Their body language is convincing.
Psychopaths lie to make themselves look good. But their nonverbal behavior is often so convincing--and distracting--that people don't recognize they're being deceitful. In the police interview with murderer and rapist Paul Bernadino, FBI agents noticed he used powerful hand gestures to distract from his spoken lies.
3. Their language lacks emotional dimension.
For psychopaths, saying, "I love you," doesn't stir up any more emotion than saying, "Please pass the milk." They can parrot back what they've heard other people say but their facial expressions don't match their words. Their ability to verbalize feelings is most likely a learned behavior, as opposed to a genuine emotional experience.
4. They sound charming.
Researchers have found that psychopaths talk more and use more emotional words in an attempt to gain attention and admiration. Psychopaths are really good at saying just the right thing at the right time. They know how to play on other people's emotions and they're master manipulators.
5. They speak slowly and quietly.
Studies show psychopaths usually speak in a controlled manner. They don't emphasize emotional words like other people do. Their tone remains fairly neutral throughout the conversation. Researchers suspect they craft a calm demeanor intentionally because it helps them gain more control in their personal interactions.
6. They talk about life in terms of cause and effect.
Psychopaths--especially those who commit crimes--talk about their behavior in terms of cause and effect. For example, one might say, "I had to teach him a lesson." Rather than show remorse, a psychopath is likely to justify his actions.
7. They focus their attention on their basic needs.
Rather than talk about spiritual or emotional needs or the needs of others, psychopaths are more likely to talk about their own basic needs, like food and shelter. A psychopath who confesses to a murder, for example, is more likely to spend the bulk of his time talking about what he ate for lunch and what he hoped to gain financially, rather than how his behavior affected other people.
8. They say, "um" more often.
Psychopaths are more likely to use filler words and sounds, like "uh" and "um." While many people use such sounds to avoid an awkward silence, researchers suspect psychopaths use them in an effort to appear sane.
9. They're great storytellers.
Whether a psychopath claims she rescued kittens from a burning building or says she was the only one at her last job who was willing to stand up to management, psychopaths tell rich stories about themselves. While some stories are likely to paint them as victims, the bulk of their stories are likely to portray them as heroes. All of their stories stem from their desire to gain trust and manipulate their listeners.
How Likely Are You to Talk to a Psychopath?
Before you start declaring everyone around is a psychopath, know that only about one in 100 people is likely to be one--unless you're talking to people in prison. Some experts estimate up to 25 percent of prison inmates may be psychopaths.
If you encounter a psychopath, don't panic. Most of them aren't serial killers. In fact, some of them are successful CEOs and business leaders. But knowing whom you are dealing with can prevent you from being manipulated.