How to quickly detect a false opinion

The Devil’s Advocate Questioning Technique


A quick, reliable technique for detecting deception in someone’s expressed opinion.


Applications: recruiting, business meetings, negotiations, partnership evaluations, heated dinner party discussions.


Evaluating the truthfulness of someone’s opinion can be quite challenging; especially when they play it safe by going along with the discussion and simply throw in a few key words that give the appearance of an opinion.
I bet you’ve done it before.  You’re involved in a group discussion and, because your opinion differs from the consensus, you nod, smile and give the appearance of agreeing with the group’s opinion.


How about a situation in the workplace where you have always suspected that one of your colleagues is a yes man?  Every idea and proposal his manager presents is always a “great idea”, “brilliant design” and “destined to succeed” in Mr Yes Man’s opinion.

Or, maybe you’re attempting to ascertain an executive job candidate’s true moral stance on, say indiscretions by people with power and influence.
By applying the Devil’s Advocate questioning technique in situations like these you will be able to manage the conversation to your deception-detecting advantage.

It works like this:

1. Ask the person an opinion-eliciting question that requires them to argue in favour of their expressed personal view.  


“Mark, I’m really interested to know why you think this new strategy is destined to succeed.  Tell me more.”

“Julie, tell me more about why you think Mayor Ford should resign.”

“Michelle, what are your reasons for supporting this new direction I’m proposing?

“Kim, I see you nodding in agreement. Why do you think Armstrong should be allowed to keep his medals?”


2. Ask the person a “Devil’s Advocate” question that requires them to argue against their personal view.


“Mark, Playing Devil’s Advocate, take me through your thoughts on why this strategy might fail?”

“Playing Devil’s Advocate here for a second, Julie, what could you say in argument for Mayor Ford keeping his job?

“Play Devil’s Advocate for me, Michelle.  What are the cons for taking this new direction?”

“Playing Devil’s Advocate, is there anything you can say against the argument that Armstrong should be allowed to keep his medals.”

3. Evaluate the length of each response.

This is where the other person’s true opinion is revealed.  The longest, more detailed response is most likely where their true opinion resides.

Why it works
In a 2001 study (Nature and Operation of Attitudes), Ajzen showed that people normally think more deeply about reasons that support — rather than oppose — their beliefs.  They are, therefore, better able to generate those reasons when asked.

In 2010, Leal et. al. conducted an experiment (Detecting True and False Opinions) where participants were required to tell the truth and lie about their opinions on various topics, including the war in Afghanistan.  The truth tellers’ opinion-eliciting answers were longer than their false answers. This allowed 75% of the truth tellers and 78% of the liars to be accurately classified.  Those are great deception detection percentages!

Over to you!

The percentages don’t lie.  Give the Devil’s Advocate questioning technique a try.
And, of course, expect to see and hear other indicators of deceptive intent, too, when the other person is giving you their false opinion.

Stay sharp!



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