IBM exec says this curveball interview question can reveal great job candidates

Harriet Green conducts an awful lot of job interviews.

As the general manager of IBM's Watson Internet of Things, customer engagement and education, Green is building a team that will eventually include more than 1,000 people and operate in the group's new headquarters in Munich, Germany.

A seasoned businesswoman and former CEO, Green has heard her share of glib answers when interviewing job candidates. To get past that she likes to throw a curve ball, asking every candidate this unique question, regardless of their background or expertise:

"The person who knows you best in the whole world, in their voice, what would they say is great about you and differentiates you? And what makes you a complete pain in the ass?"

Interviewees are almost always surprised by the question. But that's part of Green's strategy.

It makes candidates pause, especially those who, as Green puts it, talk in "this polished, slick, Silicon Valley, East Coast or London type of way."

Unexpected questions like this one can help managers get a better sense of a person, Green tells CNBC in a phone interview from Amplify, IBM's conference on customer engagement and cognitive technology.

"You stop people talking about what they want you to hear," she says. "You tend to get truth, you get reality."

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