- A liar may avoid giving specific details of a situation and respond in short, uninformative answers.
- Contrary to popular belief, liars may also fidget less and look at you directly when lying.
- They may also repeat your question before answering it, so that they have more time to think.
It can be hard to tell if someone is lying to you — especially if you don’t know them well. And some of the tip-offs you may have heard of — like people fidgeting or looking away — aren’t actually good gauges of a lie.
But there are certain speech patterns, like repeating your question or giving shorter answers, which are more reliable signs that someone is lying.
Here are eight science-backed ways to tell if someone is lying.
1. Their answers to questions may be shorter
If you ask a liar a question, they’ll often give you a shorter, more bare-bones response, than someone who’s telling the truth.
In a small 2012 study, participants were trained to recognize lies using the assessment criteria indicative of deception (ACID) method, which suggests that truthful answers tend to be longer and more vivid than lies. Before training, people recognized lies 61% of the time, and after training, their accuracy jumped to 70%.
However, answer length isn’t always a hard and fast rule. “The length of an answer does not tell us much unless we know the person and how verbose they usually are,” says Samantha Mann, a researcher at the University of Portsmouth who studies how to detect deception.
This is because “people differ vastly in how much they talk, whether lying or truth telling,” Mann says.
But encouraging someone to talk more may help you determine if they’re lying. A liar is more likely to reveal themselves in a longer story, while an honest person may provide evidence that what they’re saying is true.
For example, if someone is telling you about their day, encouraging them to say more may lead to a slip-up — like saying they went to a store, even though it’s actually closed that day.
2. They avoid giving specific details
“Liars may be less inclined to include what we call ‘verifiable details’,” Mann says. Verifiable details are details that can definitively prove their story is true or false, including:
- Exact times of events
- Names of specific locations
- Names of the people they encountered
- Their exact route to a place
- The specific words they used in a conversation
It’s normal to forget some information, especially if you’re asking about something that happened further in the past. But if the person you’re talking to seems to be intentionally vague or deflects any questions about details, this might be a sign that they’re lying.
3. They may fidget less
“Most people expect a liar to be fidgety,” says Mann, but in some cases, they may actually move less than truth tellers.
According to Mann, this is likely for two key reasons:
- People are usually unaware of how much they move, but when you lie, you may be more aware of your body language. For this reason, liars may try harder to control themselves and avoid making fidgety movements.
- Lying may require you to think harder than truth telling, because you need to remember the lie, avoid telling the truth, and invent details as needed. This intense concentration may keep your body more still, “as all energy goes to the brain,” Mann says.
4. They don’t look away while thinking
People often expect that liars will avoid eye contact during a conversation, but this is not always the case, Mann says. “If anything, liars are more likely to attempt to hold gaze, even if they don’t keep it up,” Mann says.
People who are telling the truth will often look away while they’re thinking about the answer to a question, likely as a way to help them concentrate.
In contrast, liars may avoid looking away because they’re more aware of their own eye contact and whether or not they seem dishonest.
“People who are telling the truth are not working as hard to look good,” says Kevin Colwell, a professor of psychology at SCSU who studies polygraph and forensic techniques.
Liars may also keep their eyes on you to see how you’re responding to their story and whether or not you believe them.
5. They repeat the question before answering
If you ask a liar a question, they’re more likely to repeat that question back to you before they answer, while truth-tellers are less likely to do this.
This may be because they haven’t thought of their lie yet, or need to invent a new detail in their story.
Repeating the question before answering may give them time to consider what it is you’re asking and come up with a believable story.
6. They have specific nervous tics
Liars may be generally less likely to fidget, but there are a few specific behaviors that may be linked to lying. This can include:
- They do “grooming” behaviors like smoothing their hair
- They gesture toward themselves while talking
- They press their lips together when asked a sensitive question
However, there is some doubt about whether you can use nervous behaviors to tell if someone is lying. Some experts argue that nonverbal signs of lying aren’t reliable and paying attention to behavior may not help you detect a lie.
“A truth teller also might be nervous or emotional about whatever information they are imparting,” Mann says, which might also cause nervous behaviors to show up.
7. They start out talking slowly, then speed up
When a liar answers a question, they will often start out with a longer pause and tell their story slowly. Talking more slowly can give them time to come up with a narrative or invent details as they’re going.
They may also use this extra time to watch your reaction as they speak, so they can adjust what they’re saying based on how you respond.
Once the liar has a clear sense of their story, they will often suddenly speed up their pace of talking. This may be because they think speaking too slowly will seem suspicious, so they speak faster as soon as they’re able.
This transition from slow to fast can happen in as little as one sentence. People telling the truth are less likely to show these dramatic changes in talking speed.
8. They repeat the same exact story each time
If you ask someone to repeat their story, “honest people have a memory enhancement effect from the additional recall attempt,” Colwell says.
This means that when retelling a true story, people will often add new details that they didn’t include the first time.
“Liars do not want to contradict themselves, or do anything that calls their statement into question,” Colwell says, so they’re less likely to add on details to a story like where exactly they were standing or what they were thinking.
“Liars attempt to tell the same story, in the same order, each time,” Colwell says.
The ACID method from the previously mentioned study holds that deceptive answers tend to be more rigid, carefully phrased, and less likely to change with retelling.
It’s not easy to recognize when someone is lying, but looking out for certain signs, like avoiding specifics or repeating the same exact story, may help you detect if someone isn’t telling the truth.
But it’s important to remember that these signs — especially nonverbal cues — aren’t definitive proof that someone is lying to you.
“Just because a person makes consistent eye contact it certainly doesn’t mean they are being truthful, or if a person appears to be fidgety and nervous, or behave in an odd way, it certainly doesn’t mean they are lying,” Mann says.
The most important thing you can do is to “ask for more information — the more information you can get, the more likely you are to discover whether or not you are being told the truth,” Mann says.