A growing body of research suggests general cognitive ability may be the best predictor of job performance.

Social skills, drive, and personality traits such as conscientiousness matter, too.

Companies currently place a much greater emphasis on personality traits than on IQ.

It could be wise for companies to start measuring job candidates' intelligence and personality traits, to get a more holistic picture of their potential.

"The key for us, number one, has always been hiring very smart people," Bill Gates once said in an interview. "There is no way of getting around that in terms of IQ, you've got to be very elitist in picking the people who deserve to write software."

Gates was talking specifically about Microsoft, the tech behemoth he cofounded and ran for years. But that "elitist" strategy — prioritizing raw intelligence in the hiring process — turns out to be one with surprisingly broad applications. Years of research points to the same squirmy conclusion: Smart people make better workers.

IQ versus other factors

According to Psychology Today, IQ is a construct that encompasses problem-solving abilities, spatial manipulation, and language acquisition. On an IQ test, a score of 100 is average; someone who scores 125 or above is in the top 5%. The two most common IQ tests are the Stanford-Binet and the Wechsler scales. Versions of these are now used by the military, some schools, the National Football League — and certain employers.

A recent article in the Harvard Business Review highlights three ways to identify high-potential employees: ability, social skills, and drive. "Ability" consists of cognitive ability, or IQ. The authors write: "[I]n forecasting potential to excel in a bigger, more complex job at some point in the future, the question shifts to how likely an individual is to be able to learn and master the requisite knowledge and skill. The single-best predictor of this is IQ or cognitive ability."

These conclusions are largely based on a review the authors — Tomas Chamorro-Premuzic, Seymour Adler, and Robert B. Kaiser — published in 2013, in the journal Industrial and Organizational Psychology. The review highlighted a gap between what companies look for in job candidates and what scientists say really matters to job performance. Specifically, "employers are more interested in employees' social skills than their cognitive ability."

The authors explain that their research suggests social skills matter, and so does drive. They call this three-factor model "inherently compensatory," meaning if your cognitive ability is only average, but your social skills or drive are off the charts, you still have a chance to excel at work.

As Michigan State University psychologist D. Zachary Hambrick put it, if you aren't incredibly intelligent, "acquire as much knowledge and skill as possible." Hambrick has spent a lot of time trying to debunk the myth that intelligence is overrated, and still he told me, "Cognitive ability is far from a perfect predictor of any outcome," whether that's job performance or academic performance. Even if you don't have, say, a 170 IQ, "it's not like you're doomed."

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Research on the role of IQ

The problem is that most human-resources personnel already acknowledge the importance of the ability to play nice with others and the willingness to work hard, while discounting the role of intelligence.

And at a time when more organizations are starting to embed personality testing into their hiring processes, and the term "emotionally intelligent" has become trendy in the workplace, it's worth taking a step back to get a more holistic picture of what matters to job performance.

One of the most widely cited pieces of research on the topic is a 2004 paper, published in the Journal of Personality and Social Psychology, by Frank L. Schmidt and John Hunter. The researchers reviewed dozens of studies and found that smarter people generally perform better at work, probably because smart people learn new skills more quickly.

The really surprising bit is that, while being smart is more important the more complicated your job is — think a lawyer or an accountant — it's even meaningful for relatively uncomplicated jobs.

More recently, in 2014, Wharton psychologist Adam Grant published a post on LinkedIn arguing that emotional intelligence — a term popularized by Daniel Goleman that describes the ability to identify and manage your own and others' emotions — is less important than cognitive ability when it comes to job performance. Based on the results of studies he ran on hundreds of salespeople and hundreds of applicants for sales positions, Grant concluded:

"Cognitive ability was more than five times more powerful than emotional intelligence. The average employee with high cognitive ability generated annual revenue of over $195,000, compared with $159,000 for those with moderate cognitive ability and $109,000 for those with low cognitive ability. Emotional intelligence added nothing after measuring cognitive ability."

Interestingly, Grant wrote that the CEO of the company where the study was conducted was hard pressed to believe the results were accurate.

I asked Schmidt, a professor emeritus at the University of Iowa, why he thought many people have a hard time accepting that intelligence matters at work. Here's one reason he cited:

"The concept that there is one personal trait, intelligence, which has a pretty strong genetic basis and which is very difficult to change, [that] is probably the most important determinant of where people wind up in the educational system and in the occupational structure and so forth — it seems unfair and it seems undemocratic."

Measuring IQ at work

Schmidt said that even companies that don't explicitly measure cognitive ability — say, by asking job candidates to sit for a written IQ test — may be assessing it indirectly.

He mentioned Microsoft and Google specifically, which sometimes have candidates solve problems orally during job interviews. Their performance on those problems, Schmidt said, reflects their cognitive ability. Even your standard job interview, Schmidt said, has been shown to correlate modestly with cognitive ability.

Some organizations do measure general cognitive ability directly. The NFL, for example, has rookies take the Wonderlic test, answering 50 questions in 12 minutes. The Wonderlic is also the most widely used measure of cognitive ability in the workplace; according to the company, in the past 12 months, roughly 6,000 customers purchased one of its assessment tools.

Alternatives to measuring IQ

Not all researchers subscribe to the belief that IQ is the most powerful predictor of job performance. Scott Barry Kaufman, a psychologist and the author of the 2013 book "Ungifted: Intelligence Redefined," says the emphasis on measuring IQ, and using it to determine someone's potential, can be limiting.

In a 2013 interview with Sarah Green Carmichael at the Harvard Business Review, he advised managers on how to treat employees: "Appreciating and making that person feel as though the unique, like I say, brand of intelligence they bring to the workforce, the workplace, is appreciated and valued, and that when you are very sensitive when you're creating these teams, you're very sensitive to the bigger picture in looking at all these different puzzles, all these different kinds of minds that you have as workers and helping to see who fits their value best into that bigger picture."

One solution, albeit an imperfect one, is to put job candidates through a more comprehensive screening process. That way, employers get a sense of cognitive abilities as well as personality traits.

In a 2014 New York Times op-ed, psychologist John Mayer suggested supplementing standardized tests such as the SAT with other tests that measure different cognitive abilities — for example, spatial reasoning or "'personal intelligence' — the ability to reason about a person's motives, emotions and patterns of activities." Mayer was writing about the education world, but the same logic might apply in the workplace.

Beyond the IQ test

I asked Hambrick if he thought it was important for people to know their own IQ score. Researching this topic had certainly made me want to know mine, if not to use it to meticulously plot out the rest of my career, to at least get a sense of what I could, realistically, achieve.

"Only if you want to know it," Hambrick said. "I don't think you should have to receive it if you don't want it." Hambrick doesn't know what his IQ score is — he said, "I'm not particularly interested in knowing it."