How often are you wrong?
How often do you disagree with an idea that you come across?

Or, put another way,

When was the last time you stuck your neck out and you turned out to be wrong?
When was the last time you disagreed with an idea that you came across?

While interviewing candidates for product roles, I often ask the second set of questions as they throw light on the willingness of a candidate to back up their own ideas and whether they tend to bring a curious and critical mind to discussions.

In addition, how they handle the consequent situations arising out of such actions throws light on their attitude and personality.

What's more important than asking candidates is to ask myself these questions on a regular basis.