Narcissists tend to use more offensive language
A 2014 study published in the journal Personality and Individual Differences suggests that's likely because narcissists see offensive language as attention-grabbing and because they're less sensitive to the offensiveness.
Narcissists tend to get impatient when someone else is speaking
One telltale behavior of narcissists in conversation is looking over the other person's shoulder when they're speaking, as if to seek out other interactions.
Narcissists tend to display exaggerated body language and facial expressions
The 1990 study on conversational narcissism also found that narcissists tend to be overly dramatic in their hand gestures and facial expressions.
They may also speak in a loud tone of voice.
Psychopaths and narcissists tend to tell the same fabricated stories over and over again
A blog post on Psychology Today suggests that narcissists and psychopaths both tend to repeat "confidential" information they've previously shared.
The editors who wrote the post say narcissists and psychopaths often use scripted lies: "Because people are interchangeable in the eyes of a psychopath or a narcissist—one-dimensional beings in whom they have no genuine interest—it can be hard for them to remember what they've said, and to whom."
Read next on Business Insider: 9 subtle signs that you're talking to a psychopath