"People skills" are almost always assumed to be a good thing.

Search employment ads and you will find them listed as a qualification for a startling array of jobs, including Applebee's host, weight-loss specialist, CEO, shoe salesperson, and (no joke) animal-care coordinator. The notion that people smarts might help you succeed got a boost a quarter-century ago, when the phrase emotional intelligence, or EI, entered the mainstream.

Coined in a 1990 study [1], the term was popularized by Daniel Goleman's 1995 book [2]. Since then, scores of researchers have shown how being in touch with feelings — both your own and other people's — gives you an edge: Compared with people who have average EI, those with high EI do better at work [3], have fewer health problems [4], and report greater life satisfaction [5].

There's a catch, though: other researchers have recently examined what they call "the dark side" of EI, and their findings suggest an unnerving link between understanding people and using them.

Last year, a group of Austrian psychologists 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 [6]. Similarly, a 2014 study linked "narcissistic exploitativeness" with "emotion recognition" — those who were prone to manipulating others were better at reading them [7].

Another study found that "Machiavellians" (those who rated high on a scale of "Machiavellianism" — essentially, manipulativeness) with high EI were more likely to have publicly embarrassed someone else for self-promotional reasons [8].

Happily for the rest of us, there don't seem to be many emotionally intelligent Machiavellians on the loose — Scottish researchers found Machiavellianism to be inversely correlated with EI [9].

Less happily, at least for those of us with jobs, the workplace seems to provide ample opportunities for people with high EI — be they narcissists, Machiavellians, or everyday strivers — to behave deviously. A 2010 journal article reviewed "self-serving" uses of EI in office settings, such as "focusing on strategically important targets" (subordinates, rivals, supervisors) and working to "distort, block or amplify rumors, gossip, and other types of emotion-laden information" [10].

Finally, a note of caution to those hoping high EI might help them get ahead: It is not always an asset.

In a 2013 study, college students were shown news footage of people pleading for a missing family member's return — half of whom were in fact responsible for the person's disappearance. When the students rated the sincerity of these pleas, those with higher EI were more likely to be duped, perhaps due to overconfidence in their ability to read others [11].

So don't underestimate people skills — but don't overestimate them, either. Reading emotions doesn't mean you can read minds.

The Studies:

[1] Salovey and Mayer, "Emotional Intelligence" (Imagination, Cognition, and Personality, 1990)

[2] Goleman, Emotional Intelligence (Bantam, 1995)

[3] Wong and Law, "The Effects of Leader and Follower Emotional Intelligence on Performance and Attitude" (The Leadership Quarterly, June 2002)

[4] Mikolajczak et al., "Explaining the Protective Effect of Trait Emotional Intelligence Regarding Occupational Stress" (Journal of Research in Personality, Oct. 2007)

[5] Saklofske et al., "Factor Structure and Validity of a Trait Emotional Intelligence Measure" (Personality and Individual Differences, March 2003)

[6] Nagler et al., "Is There a 'Dark Intelligence'?" (Personality and Individual Differences, July 2014)

[7] Konrath et al., "The Relationship Between Narcissistic Exploitativeness, Dispositional Empathy, and Emotion Recognition Abilities" (Journal of Nonverbal Behavior, March 2014)

[8] Côté et al., "The Jekyll and Hyde of Emotional Intelligence" (Psychological Science, Aug. 2011)

[9] Austin et al., "Emotional Intelligence, Machiavellianism and Emotional Manipulation" (Personality and Individual Differences, July 2007)

[10] Kilduff et al., "Strategic Use of Emotional Intelligence in Organizational Settings" (Research in Organizational Behavior, 2010)