Top executives don't always have the time to interview every job candidate. But when they do, they want to make sure they ask the right questions.

What's a good interview question?

There's no textbook play here, but according to these CEOs and executives, it doesn't always have to be smart and formal.

Here's a list of some of the most unusual interview questions they like to ask:

Lars Dalgaard, Venture capitalist at Andreessen Horowitz and former CEO of SuccessFactors

Question: "What did you learn from your mom?"

Why: Dalgaard says it's an "incredibly powerful" question that could give a much better clue about the person's emotions. "Basically I'm testing them to see, 'How human are you ready to be with me?'" he told The New York Times.

Stewart Butterfield, CEO of work-messaging app Slack

Question: "What century was the French Revolution in?"

Why: Although Butterfield doesn't ask this question any longer, he says the goal was to see if the candidate is curious about the world. Now he always asks what they want to be when they grow up instead.

César Melgoza, founder and CEO of business-intelligence firm Geoscape

Question: "What magazines and books have you read recently? What do you do in your spare time?" 

Why: Melgoza says these questions help give him a sense of what motivates his interviewees. "The question it answers for me is, 'Are you investing in yourself?'" he said.

Yasmin Green, head of research and development at Jigsaw --Alphabet's tech incubator formerly known as Google Ideas

Question: "How would you make money from an ice-cream stand in Central Park?"

Why: "I'm curious to see how people deal with ambiguity and whether they can have fun while thinking on their feet," she said.

Don Charlton, founder and CEO of the software recruiting firm Jazz

Question: "If you failed at this job in your first 90 days, what things wouldn't you be doing well?"

Why: Charlton says it's a good way to find out if the candidate is self-aware. "You want the candidate to recognize the aspects of themselves where they can be confident and the parts they're going to need for them to be successful in a new company," he said.

Lori Senecal, CEO of the MDC Partner Network and global CEO of advertising agency CP+B

Question: "What have you invented?"

Why: "That doesn't mean you have to have created a robot that can get a beer from a fridge. It could be anything. It's to see whether they have the mind-set of creating something. That shows a desire to find fresh solutions," Senecal said.

Andy Bryant, Intel Chairman

Question: "Which classes were your best classes?"

Why: "It comes down to intellect, a track record of success, and a desire to be at Intel. If I can find people who have those criteria, I can generally make it work," he said.

Gary Smith, CEO of broadband and telecommunications company Ciena

Question: "How can I tell if you're having a bad day, and how does that manifest itself?"

Why: "If they say they become quiet, then I'll ask, 'Tell me what comes next? How do you deal with it? Do you walk away from the issue?' And I'll drill down on that, because it leads to a lot of good discussions around what motivates them, and what they enjoy about their work and what they don't like about it," he said.

Mary A. Laschinger, CEO of Veritiv Corporation

Question: "How do you get things done?"

Why: Laschinger says she asks this question to get three things out of the job candidate: their values, willingness to learn, and their technical capabilities. "Did they engage across the organization? What did they have to do to get it done? Tell me about some successes with people specifically, good outcomes and bad outcomes," she said.

Stormy Simon, president of online retailer Overstock

Question: "If you were an animal, which animal would you be?"

Why: "The animal kingdom is broad, and everyone can identify with a specific animal they think embodies their own personalities and characteristics," she said.

David Politis, CEO of cloud-based software maker BetterCloud

Question: "What would be your dream job if you could do anything in the world?"

Why: "My next question is, 'Why aren't you doing that?' Those two questions will tell you a lot about people's passions and their fears," he said.

Lorna Borenstein, founder and CEO of online cooking, yoga, and fitness-video maker Grokker

Question: "Share your life story."

Why: Borenstein starts every interview by sharing her own life stories. She wants the interviewee to know where she's from and then wants to hear the same from them. "I want to understand what makes you tick and what your competencies are, and then to hear about examples of when you either got it right, or when you got it wrong, and what you learned from it," she said.

Joshua Reeves, CEO of payroll app Gusto

Question: "I kind of channel my inner 4-year-old, and I ask a lot of 'why' questions."

Why: Reeves doesn't focus on a candidate's skills or work experiences. Instead, he tries to ask why the person made certain decisions at important points in their life. "If you keep asking why, you'll get to the meat of it, which is when someone leaves behind trying to think about the right answer, and you get to questions about purpose, and what motivates you," Reeves explained.

Tobi Lütke, CEO of Shopify

Question: "Our hiring is almost completely built around just going through someone's life story, and we look for moments when they had to make important decisions, and we go deep on those."

Why: "I find that the strongest predictor of people who will do well at Shopify is whether they see opportunity as something to compete for, or do they see opportunity as essentially everywhere and unlimited? It's a rough proxy for pessimism and optimism," he said.

Lori Dickerson Fouché, CEO of Group Insurance at Prudential Financial

Question: "What kind of cultures do you like to work in? Where do you excel? How do you excel? If you find yourself in situations where they're not going the way you want them to, what do you do?"

Why: Fouché says the goal is to find resilience and perseverance in the candidate's responses. "How people conduct themselves when they face challenges is really important," she explained.

Melanie Whelan, CEO of SoulCycle

Question: "Tell me about your background."

Why: "It's a great way to warm up any conversation, and it really helps me understand how you communicate. Are you linear, concise, and direct? Or are you a storyteller? Are you entertaining? Do you go off on tangents?" she said.

Cindi Leive, editor-in-chief of Glamour magazine

Question: "I always ask people why they want the job."

Why: "There's not one right answer, but I want to see that there is a reason," she said.

This story first appeared on  Business Insider