"The power to do good is also the power to do harm."

--Milton Friedman

If you follow my column, you know I'm a fan of developing emotional intelligence. Put simply, emotional intelligence (EI) is a person's ability to recognize and understand emotions (both his or her own and that of others), and use that information to guide decision making.

But recently, many have been asking me the same question, namely:

If emotional intelligence is so great, why do we see many "successful" people who seem to lack this quality?

While the answer is complex, a big part of it might surprise you:

Emotional intelligence can easily be used for evil.

The Dark Side

For example, consider the following scenarios:

A political candidate who plays on a crowd's fears and emotions to gain favor, despite his or her hidden agenda

A husband or wife who hides an extramarital affair so that (s)he can string along both mate and lover

A manager or employee who distorts the truth, or purposefully spreads unconfirmed rumors and gossip to gain a strategic advantage

Each of these examples requires using a certain degree of EQ, albeit in a manipulative and deplorable way.

The truth is, emotional intelligence is a lot like "normal" intelligence, or any other ability for that matter: You can hone your skills and use them for either good or evil. Much like someone with a brilliant mind could become a lifesaving surgeon or a serial killer, one with superior EQ has a choice between two very different paths.

For example, Andrew Giambrone of The Atlantic shared research from one group of Austrian psychologists who reported "a correlation between EI and narcissism, raising the possibility that narcissists with high EI might use their 'charming, interesting, and even seductive' qualities for 'malicious purposes,' such as deceiving others. Similarly, a 2014 study linked 'narcissistic exploitativeness' with 'emotion recognition'--those who were prone to manipulating others were better at reading them."

Scary, right? It gets worse.

Organizational psychologist and best-selling author Adam Grant identified EI at its worst in his article, The Dark Side of Emotional Intelligence:

"Recognizing the power of emotions...one of the most influential leaders of the 20th century spent years studying the emotional effects of his body language. Practicing his hand gestures and analyzing images of his movements allowed him to become 'an absolutely spellbinding public speaker,' says the historian Roger Moorhouse--'it was something he worked very hard on.' His name was Adolf Hitler."

As Grant points out, the unbridled enthusiasm for emotional intelligence has obscured a dark side.

"New evidence shows that when people hone their emotional skills, they become better at manipulating others," says Grant. "When you're good at controlling your own emotions, you can disguise your true feelings. When you know what others are feeling, you can tug at their heartstrings and motivate them to act against their own best interests."

In the documentary Fatal Attraction of Hitler, observer Egon Hanfstaengl noted that Hitler was remarkably skilled in this area:

"He had that ability which is needed to make people stop thinking critically and just emote...The ability derived from his readiness to throw himself totally open--to appear bare and naked before his audience, to tear open his heart and display it."

This is in line with research Grant highlights by University of Cambridge professor Jochen Menges. Menges's studies document that an audience "was less likely to scrutinize" a leader's message when he or she gave "an inspiring speech filled with emotion". Ironically, although audience members claimed to recall more content from the speech than they would typically, they actually remembered less.

Why Emotional Intelligence Is More Important than Ever

So, with all of these potentially dreadful uses of emotional intelligence, does that mean you shouldn't try to develop it?

To the contrary, this is all the more reason to heighten your EQ. Used ethically, emotional intelligence can help gain advantage for both you and those you are dealing with. Even more importantly, though, if someone tries to use emotional intelligence for nefarious purposes, your EI can help you identify this--and take appropriate action to counter.

Of course, not everyone who is "successful" has a high EQ; there are countless other factors at play. And being careful doesn't mean you need to be overly suspicious...or constantly impute wrong motives to others. (Even the most emotionally intelligent person is far from a mind reader.)

But a high EQ will help you gain more control in a situation, so that you aren't easily duped or taken advantage of.

Putting It Into Practice

Remember: Emotions are powerful.

Being mindful of this allows you to use emotions for you, instead of against you. However, like any skill, people will use emotional intelligence for both honorable and devious purposes.

How will you use this extraordinary tool?