What makes a great leader? Some say there’s a perfect formula: combine the right skills with the right ambition and opportunity, and anyone can achieve success. But now research says it’s what you can’t see on a resume that may matter most.

Up to 85% of our financial success is based on “invisible skills”—traits like personality, how well we can communicate, and our ability to empathize, negotiate, and lead. These non-technical skills may not be as obvious on paper like a degree or job experience, but they’re the foundation for something just as important: our emotional intelligence. Also known as “EQ,” this unseen mental quality is found in many of the world’s top leaders, and may just be the the deciding factor between a good business leader and a great one.

What is your emotional intelligence?

According to Psychology Today, emotional intelligence is “the ability to identify and manage your own emotions and the emotions of others.” In business (especially sales), this is often referred to as being good with people or having good people skills. But emotional intelligence isn’t just about how well we interact with each other. It’s also about how well we manage and interpret our own emotions.