“There’s no such thing as a human lie detector,” according to Philip Houston, Michael Floyd and Susan Carnicero in their must-read book Spy the Lie: Former CIA Officers Teach You How to Detect Deception. But there are still ways you can learn to spot lies.

In fact, even a polygraph can’t distinguish fiction from fact. What a polygraph can do is detect physiological changes that occur after a person is asked a question. Focusing on what a person does after they’re asked a particular question is essentially how Houston, Floyd and Carnicero suggest readers detect deceit.

According to the model which Houston developed, after you ask the person a specific question, pay attention to their behavior within the first five seconds. This involves both looking at their behavior and listening to what they say.

Why five seconds?

The authors explain that if the first deceptive behavior occurs within five seconds, then you can assume that it’s associated with your question. (The more time elapses, the likelier it is that the brain is thinking about something else).

But one deceptive behavior doesn’t a liar make. After you spot the first deceptive behavior, watch out for additional deceptive behaviors. The authors refer to this as a cluster: “any combination of two or more deceptive indicators,” which can be verbal or nonverbal.

The chief principle of this model stipulates that if you want to detect deceit, you need to ignore the truth. Here’s why: a person who’s lying to you may try to trick you with the truth. They’ll use truthful statements to steer you away from their deception.

For instance, Floyd was hired to administer a polygraph to a student who was accused of cheating on midterm exams. The student brought an album of photos he’d taken in his native country (some photos featured him with dignitaries) to the polygraph appointment. This was the truth.

But it was clear these photos were an attempt on the student’s part to convince Floyd he was a good person, and simply not the cheating kind. (Floyd also thoroughly assessed his behavior before the polygraph, and it was clear that the student was guilty).

Ignoring the truth, according to the authors, helps us keep our biases in check and reduce the amount of extraneous information we need to process.

What Lies Look & Sound Like

The authors devote several chapters to explaining what deception sounds and looks like. For instance, people who are lying might evade your question, or say statements such as, “I didn’t do anything,” or “I’d never do that.”

They also might repeat the question, worried that their silence will signal guilt. They might appeal to religion and say phrases like, “God knows I’m telling the truth.” They might inundate you with details. For example, when Houston was in charge of internal affairs at the CIA, he required that during interviews, investigators ask employees about their job descriptions.

Interestingly, truthful employees tended to respond in a few words such as “I’m a case officer,” whereas people who were lying gave more thorough descriptions. Everything in their descriptions was true. But their goal was to create a positive impression and bury their deceit in different facts.

Deceptive people also might be overly nice and polite. As the authors point out, they might say “Yes, ma’am” when lying to your specific question. They might use qualifying words such as, “basically,” “probably” or “to be perfectly honest.”

According to the authors, most communication is actually nonverbal. So paying attention to the person’s behavior right after you ask your question is key. For instance, a person who’s lying to you might close their eyes (blinking excluded) when responding to your question, or they might put their hand in front of their mouth.

Throat-clearing or swallowing before a person answers your question is also problematic. According to the authors, they “might be doing the nonverbal equivalent of the verbal, “I swear to God…’” or they might’ve experienced a surge of anxiety leading to dryness in their mouth.

Anxiety can also trigger what the authors call “grooming gestures.” They note that a deceitful man might adjust his tie or glasses. A deceitful woman might put her hair behind her ears or adjust her skirt.

Lying individuals might start straightening up their environment right after your question, such as moving a glass of water. (By the way, count grooming gestures in response to one question as one deceptive behavior).

Questions to Ask to Spot Lying

This model is only as good as the questions you ask. According to the authors, open-ended questions are helpful when you’re trying to collect information for your discussion. For instance, you might ask, “Tell me what you did yesterday after you arrived at the office.”

If you’re looking for specific facts, ask closed-ended questions (“Did you log on to Shelley’s computer yesterday?”). Presumptive questions presume something (“What computers on the network have you logged on to besides your own?”) Usually if a person is lying, they’ll take extra time to process your question to figure out how to spin their story.

The authors also suggest keeping your questions short, simple and straightforward.

Check out the authors’ company website here.