To Catch a Liar, Ask These Two Questions: The Psychology Behind Contradictions
Have you ever had the feeling that someone isn’t telling you the whole truth?
Maybe their story changes slightly each time they tell it. Perhaps the details don’t quite fit together, or you notice that their explanation seems different from what they said earlier.
There is a popular psychological technique that claims you can expose a lie by asking two simple questions:
“Can you tell me exactly what happened?”
and later:
“Can you tell me the same story, but starting from the end and working backward?”
The idea sounds clever—but there’s an important catch.
No two questions can reliably determine whether someone is lying.
Why asking for the story twice can reveal inconsistencies
When people describe a real experience, they often remember it through connected details: where they were, what happened next, who was present, and how they felt.
Asking someone to explain an event in a different order can require more mental effort.
Someone who is deliberately inventing a story may have difficulty keeping every invented detail consistent.
But that doesn’t mean an inconsistency automatically proves deception.
Human memory isn’t a video recording.
A truthful person can forget a detail, remember events in the wrong order, become nervous, or describe something differently when asked the same question twice.
A better question to ask
Instead of trying to “catch” someone, investigators and interviewers often focus on open-ended questions.
For example:
“Tell me everything you remember about what happened.”
Then, after they finish:
“What happened immediately before that?”
These questions encourage the person to provide information rather than simply answering yes-or-no questions.
Don’t mistake nervousness for lying
This is one of the biggest mistakes people make.
Someone avoiding eye contact, fidgeting, sweating, speaking quickly, or appearing nervous isn’t necessarily lying.
They could simply be uncomfortable.
Research has repeatedly shown that people are generally not very accurate at detecting deception based solely on behavioral cues. There is no single body-language signal that reliably identifies a liar.
Look for evidence, not just behavior
If someone’s story seems contradictory, don’t immediately conclude that they’re lying.
Instead, ask:
- What exactly changed in the story?
- Could the difference be explained by memory?
- Is there independent evidence?
- Does the timeline make sense?
- Can the important facts be verified?
The strongest indication of deception usually comes from inconsistencies combined with evidence, not from a person’s posture or facial expression.
The two-question trick isn’t a lie detector
The idea of asking someone to tell a story forward and backward can be useful as an interviewing technique because it encourages detailed recall and may reveal inconsistencies.
But it shouldn’t be treated as a scientific “two-question lie detector.”
A truthful person can contradict themselves.
A practiced liar can remain consistent.
And sometimes the truth is much more complicated than either person initially remembers.
So the next time you suspect someone isn’t telling you everything, resist the temptation to play detective.
Ask open questions.
Listen carefully.
Check the facts.
And remember:
A contradiction is a reason to investigate—not proof that someone is lying.