For most of us, the label "psychopath" summons images of cold-blooded serial killers. But psychopathy is a complex condition that scientists still struggle to fully understand.

Professor Robert Hare has spent his life studying psychopaths. A criminal psychologist, he is the creator of the PCL-R, a psychological assessment used to measure psychopathic traits in an individual. It measures if and how individuals display behaviors such as pathological lying, a grandiose sense of self-worth, cunning manipulation, a lack of behavioral control and remorse, and an unwillingness to accept responsibility for actions (among others).

Interestingly, Hare believes psychopathy is dimensional.

"There are people who are part-way up the scale, high enough to warrant an assessment for psychopathy, but not high enough up to cause problems," said Hare in an interview with The Telegraph. "Often, they're our friends, they're fun to be around. They might take advantage of us now and then, but usually it's subtle and they're able to talk their way around it."

My forthcoming book, which serves as a practical guide to emotional intelligence, outlines how psychopaths (and those exhibiting certain psychopathic traits) use your emotions against you to get what they want.

Here are a few of their methods:

1. They use empathy to their advantage.

Traditionally, scientists have argued that psychopaths aren't capable of feeling empathy. But that's not entirely true.

"There are two kinds of empathy. Cognitive empathy is the ability to know what other people are feeling, and emotional empathy is the kind where you feel what they're feeling," explains James Fallon, a neuroscientist at the University of California and the author of The Psychopath Inside: A Neuroscientist's Personal Journey Into the Dark Side of the Brain.

Psychopaths are specialists in cognitive empathy. "This all gives certain psychopaths a great advantage, because they can understand what you're thinking, it's just that they don't care, so they can use you against yourself," Fallon says.

2. They can turn emotions on and off.

Dr. Christian Keysers, who heads a lab at the Netherlands Institute for Neuroscience, studied 21 convicted violent psychopathic offenders to learn more about how they experience emotion. Patients were shown movies of people hurting each other while brain activity was measured using a brain scanner.

"The results of the study indicate that the vicarious activation of...emotional brain regions was much lower in the patients with psychopathy than in the normal subjects," explains Keysers.

A fellow researcher then suggested the patients watch the movies again, but this time they should try and empathize with the victims in the movies.

"What we found was that this simple instruction sufficed to boost the empathic activation in their brain to a level that was hard to distinguish from that of the healthy controls. Suddenly, the psychopaths seemed as empathic as the next guy. Their empathy was switched on."

"So psychopathic individuals do not simply lack empathy.... If they want to, they can empathize, and that explains how they can be so charming, and maybe so manipulative."

3. They use fear against you.

Research indicates that psychopaths don't experience fear like the rest of us.

For example, how do you react if you're suddenly startled by a loud noise? Most individuals will jump or immediately develop sweaty palms. However, experiments show that psychopaths barely startle--and their hands stay dry.

Again, cognitive empathy comes into play. And this is part of what makes psychopaths dangerous: They can manipulate situations or exaggerate facts to scare you into action, without feeling fear themselves.

4. They deceive.

Since psychopaths are concerned primarily with reaching their own goals, deceit is viewed simply as a means to an end. They present a distorted view of reality by exploiting one side of a story or entwining truth and lie so well that it's difficult for many to distinguish fact from fiction.

5. They choose to remain ignorant.

James Blair, Derek Mitchell, and Karina Blair are neuroscientists who study mood and anxiety disorders. In their book The Psychopath: Emotion and the Brain, they state the following:

Whereas most people automatically anticipate the consequences of their actions, automatically feel shame for unkind deeds, automatically understand why they should persist in the face of frustration, automatically distrust propositions that seem too good to be true, and are automatically aware of their commitments to others, psychopaths may only become aware of such factors with effort.

In other words, it's probable that many psychopaths say and do things without any feeling of shame or thought of how those actions affect others--allowing them to take whatever action they desire in the pursuit of their own self-aggrandizing goals.

You never know when life will bring you into direct contact with a psychopath--or at the very least, one who exhibits traits that are commonly identified with psychopathy.

And that's exactly why you should sharpen your own emotional intelligence--to protect yourself when you need it the most.