How to become a human lie detector – understanding the science of deception
The business world has no shortage of shonky dealers using deceptive tactics in order to fleece a business out of hard-earned cash, products or services – or worse, to worm their way into your business. But how do you spot a liar before you decide to deal with them? It’s all in understanding the science of deception, says our Partner, Alex Martin.
Over the years he’s spent in the courtroom and the boardroom, Alex has a pretty good idea if someone is lying to him. He’s interviewed hundreds of witnesses and thousands of clients.
In his experience, Alex says you can get close to the truth by forensically analysing someone’s story against the available evidence; that’s what lawyers do.
However, when running a small business, you rarely have the time or the information to test someone’s story. Instead, you have to rely on a gut feeling about whether someone is telling the truth – the sense that something wasn’t right with their story or behaviour.
While a gut feeling has its place in business, it is possible to pick a liar much more accurately and reliably. The answer is in the science.
How to spot a liar from a thousand paces
Human beings are actually very bad liars. Believe it or not, most people don’t want to lie and send very strong signals when they do – signals you can learn to identify and read.
The first step to separating the truth from the lie is to identify a baseline of behaviour and language. How does the person behave when they are comfortable and truthful? Are they fidgety and vague, or calm and precise?
Once you have a baseline, you need to formulate the right questions and listen very carefully to the answers.
The questions need to directly and specifically address the relevant allegation. Don’t imply a question or make the question too long to follow.
Asking short, direct questions such as, “Did you read this email on Monday?” is much better than, “You would have understood the emails sent to you, wouldn’t you?”. The second question gives too much latitude to deceive without directly lying.
Avoiding a lie
The next step is the most important: Listen carefully to all the person’s answers, including what happened before and after the part you are interested in.
People will work very hard to avoid telling a lie, if they can. They will just skip over that part if the interviewer allows it; or they will address a different question about the same issue to avoid lying, like Lee Harvey Oswald’s public statement:
Question: “Did you kill the president?”
Answer: “I have not been charged with that.”
If they are clever, they might give an answer that addresses the question that is technically true, but is intended to deceive. The most famous example is President Clinton’s statement:
“I did not have sexual relations with that woman, Ms Lewinsky.”
This statement is hardly a statement of full and frank honesty.
To avoid telling a direct lie, witnesses will often:
- Not answer the question;
- Leave out the critical fact;
- Pretend to forget;
- Pretend they don’t know.
All of the above are indicative of deception when compared to the person’s baseline, or the rest of their evidence.
The numbers also show that people use different language when they are telling a lie.
Specific statements made in the ‘first person active past tense’ (“I walked the dog on Saturday”) are indicative of truth; while more vague statements in the passive tense (“The dog would have been walked by me on Saturday”) are indicative of deception.
You might think that nobody would be that vague, but Alex has seen it happen. In fact, he’s seen witnesses use very clear, specific, active, first-person language for part of their evidence, then suddenly switch to more passive and vague language for the part that is not true, then switch back again when they return to the truth. Alex says it is amazing to watch!
You never lie twice
Another shocking truth is that people will avoid lying about their previous lie – they can lie on multiple occasions in one statement, no problem, but they struggle to lie on two different levels about the same issue.
You can catch them out by asking them about the relevant factual conduct, listening to the answer, then asking about the truthfulness of their statement. The first question is about a statement of fact, and the second is about their truthfulness on the statement of fact.
Generally, deceptive witnesses will struggle to give a clear lie twice. For example:
Question: “Did you take the money?”
Follow up question: “Should I believe you?”
Generally, a truthful witness will answer the second question with, “Yes, of course”, or something similar. A deceptive witness will give a vague answer like, “I guess so”, or even an accurate answer like, “That is up to you”.
Something about the different levels of logic makes it very difficult for deceivers to directly lie twice about the same issue. Truthful witnesses don’t have that problem.
Even the smallest detail, like the time they spend on an answer, is telling. The statistics show that around 85 per cent of deceptive witnesses spend more time on the truthful parts of their stories, than the lies.
People don’t like to lie. The lie is likely to be the quick, vague, passive part of the statement in comparison to the baseline for that witness.
If that is not enough, people also give unconscious cues in their language. They give you information they don’t want you to have; they can’t help it. For example, if a witness says:
“I had lunch with someone”
“I had lunch with a friend”
“I had lunch with a girlfriend”
“I had lunch with my girlfriend”
Each of these statements indicate very different levels of closeness and trust between the people at the lunch. This becomes more interesting when they answer questions that were not asked, but they feel guilty about.
For example, when asked what he did on the evening of the shooting of his girlfriend, Oscar Pistorius, answered, “Reeva would have gone out with her friends (a lie) … but we were content to have a quiet dinner together at home” (another lie). He starts vague about what she ‘would have done’, then goes on to answer a question that was not asked – “Were you both happy about staying home that night?”
The clear indication is that they were not happy about being at home that night. The couple were probably fighting about her going out with her friends; a clue to jealousy being the motive for the shooting.
People tell you exactly what they don’t want you to know. They almost want to tell you because of the unconscious guilt of lying. That guilt even applies to people who appear to have very poor ethics.
The final category of clues to deception are non-verbal.
Some are physiological, like blood pressure and saliva; and some are behavioural, like eye movement, body language and micro-expressions. Again, having a baseline for the person when they are relaxed and truthful is critical.
Eye movement, cheek redness, mouth dryness, body language, etc, which is consistent with the witness’ usual level is indicative of truth, while changes in the pattern is indicative of deception.
Usually, extroverted people with good people skills look you in the eye when they lie, while introverts look away. So, whether they look you in the eye on its own tells you nothing, but compared to the person’s usual baseline behaviour, it tells you a lot.
They key is to watch the witness and listen carefully to what they say. Record it all if you can, and watch it back. Or better yet, have their words transcribed and read them carefully. The answers you seek might be right under your nose.
If you wish to discuss a particular issue, please do not hesitate to reach out to our team for a confidential chat on (03) 9481 2000 or by emailing us at email@example.com.