You're probably familiar with the networking terms "weak ties" and "strong ties," but chances are you haven't heard of "dormant ties."

According to Wharton business professor Adam Grant, this third category of contacts should not go overlooked. Dormant ties refer to people you used to know but have since lost touch with.

During a conversation with Inc. president and editor-in-chief Eric Schurenberg, Grant explained why dormant ties can be better for networking than weak or even strong ties.

"Research demonstrates that when you need advice on a project, you get better information when you reach out to someone you used to know than someone you currently know," he says.

The idea is that strong ties tend to give you redundant knowledge, as they are likely to know the same people and same things you do, but dormant ties have a much more diverse network.

"They've been meeting different people and learning different things in the last few years, so they can open up whole worlds you didn't know existed," Grant says.

While weak ties may also have a broader set of contacts, developing a strong relationship with weak ties can be difficult.

"Unlike your weak ties, it's actually comfortable to reach out to [dormant contacts] because you have that shared experience, the common history. It's a lot easier to reconnect than to start a connection from scratch."

For more tips from Grant's book, "Give and Take: A Revolutionary Approach to Success," watch the video below.