The prototypical Silicon Valley star is perceived as a genius from Stanford, MIT or Harvard who's technically brilliant, inspires with vision, and carries the day. It even used to seem impossible to get a job at Google if you weren't a Stanford or MIT grad. As recently as 2012, even if you'd been out of college for 10 years, they would still ask you for your college GPA and what you made on the SAT in high school.

Yet that's not at all what Google has discovered are the most important qualities. Google is a company that's obsessive about looking at data to determine what makes employees successful leaders, and the numbers showed something surprising.

The prototype is completely wrong.

The most important character trait of a leader isn't where she went to school or her IQ. It's one that you're more likely to associate with a boring person than a Silicon Valley star: predictability. The more predictable you are, day in and day out, the better.

Google People Operations' data-driven decision-making

Google is famous for being one of the most data-driven companies in the world--even in the area of HR, where decisions in other companies are still made largely based on gut. The search giant has an entire team dedicated to "people analytics," whose job it is "to apply the same rigor to the people side as to the engineering side." Google takes this extremely seriously: "All people decisions at Google are based on data and analytics," according to Kathryn Dekas, a manager in this team.

By taking an evidence-based approach rather than a gut-driven one, Google has been able to debunk conventional wisdom on how to build an A team. For example, twice a year, all employees review their bosses in an "upward feedback survey," evaluating 12 to 18 factors. Tens of thousands of job candidates have gone through Google's hiring process, which can be scrutinized to see whether interview performance correlates with on-the-job success.

Crunching the numbers on the question of what makes a successful leader, Google found out that leaders must be predictable and consistent. When managers are predictable, they eliminate an obstacle from employees' progress--themselves. Managers have their own tendency to interfere, dictate, second-guess, and be a backseat driver. Without this obstacle, employees don't have to worry about whether their manager will try to jump in or suddenly veer in a different direction. Instead, they have the mental space to do great work.

On the flip side, as Laszlo Bock, senior vice president of people operations at Google, puts it, "If your manager is all over the place, you're never going to know what you can do, and you're going to experience it as very restrictive." But "[i]f a leader is consistent, people on their teams experience tremendous freedom."

The kicker is that Google's use of data is so powerful that it was able to refute the bias of the company's founders Larry Page and Sergey Brin. Both are top university grads with high GPAs, and when the company was founded, Page and Brin looked only for candidates whose elite educational background mirrored theirs. "For years, candidates were screened according to SAT scores and college grade-point averages, metrics favored by its founders," says Prasad Setty, vice president for people analytics.

However, even the founders couldn't argue with the data, and this new discovery actually changed organizational behavior. Now candidates are evaluated on interview questions that examine their complex problem-solving abilities.

Autonomy is the key to employee happiness and outsized performance.

The freedom that a consistent leader provides is a powerful force because having autonomy over your work is one of the best motivators of personal productivity.

In 2004, psychologists Edward Deci and Richard Ryan conducted a study of hundreds of associates at an investment bank on their job satisfaction. They found that the highest job satisfaction ratings came from employees whose bosses facilitated their work as the employee--rather than the manager--saw fit. These bosses provided "autonomy support": acknowledgment, encouragement, and structure around getting work done.

The result wasn't just happier employees. Deci and Ryan also discovered that the employees with autonomy were also the ones with the highest job performance. Google made a similar finding. Its most successful employees "are those who have a strong sense of mission about their work and who also feel that they have much personal autonomy."

All of this dovetails with author Daniel Pink's work. In his #1 New York Times bestselling book, Drive, he concluded that the source of human motivation and our best work comes from our inherent drive toward autonomy, mastery, and purpose. This can clash with high-prestige and credentialed individuals who are driven by external recognition and rewards, not curiosity and craft.