PDF Summary:Spy the Lie, by Philip Houston, Michael Floyd, and Susan Carnicero

Have you ever had the feeling someone was lying to you...even when every word from their mouth seemed true?

In a world where truth and lies seem always to be intertwined, Spy the Lie gives you the tools to cut through distracting and misleading details—with effective questions and a sharp eye for suspicious “tells,” you’ll know when someone is trying to deceive you or hide the truth. Written by CIA veterans Philip Houston, Michael Floyd, and Susan Carnicero—and former NSA analyst Don Tennant—this book teaches techniques they refined over years of interviews with informants and suspects.

Our guide to Spy the Lie covers the authors’ guidance for applying their techniques in your life. We'll explain how to ask effective questions (and avoid the wrong questions), what responses signal deception, and how to verify that a suspicious response is truly deceitful—not just a fluke. Our commentary extends the authors’ ideas with supporting research, offers alternative explanations for suspicious behavior, and explains how quirks of human behavior affect responses.

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(Shortform note: This isn’t to say you can’t ask these types of questions at all—you'll need to ask nonrelevant questions in any conversation, like when talking to coworkers or family. This piece of advice only refers to the part of the conversation where you’re looking for specific information and will be watching and listening for signs of deception after your questions. Outside of this part of the conversation, feel free to ask irrelevant questions—but don’t waste your mental bandwidth closely observing the replies.)

Trait #2: They’re as Short as Possible

By asking brief questions, you encourage the interviewee to respond quickly and instinctively—often leading to slips or inconsistencies in their story that might indicate a lie. On the other hand, if you ask long questions that give the interviewee time to think while you’re speaking, she can more easily create false details to fit her existing narrative.

(Shortform note: Research suggests that forcing a quick answer may not be as useful to pinpointing deception as the authors say. Not only are people biased to believe a quicker response is more truthful than a slower response, giving you another bias you need to overcome, but an interviewee under pressure may be more likely to give an answer that makes them look virtuous—rather than giving you the truth.)

Trait #3: They’re Loaded, Not Leading

Leading questions imply one possible, simple answer—usually “yes” or “no.” On the other hand, loaded questions imply that you know some information about the interviewee and what his response should be. This causes your interviewee to spend a lot of mental effort on trying to figure out how much, and what kind of, information you know and carefully deciding on an answer that won’t conflict with that information.

For example, “You did X while I was gone, didn’t you?” is a leading question that suggests a simple “yes” or “no” response. On the other hand, “What did you do while I was gone?” is a loaded question that implies you know that something happened and requires a longer answer.

(Shortform note: Even though leading questions generally won’t clog up your interviewee’s mental bandwidth like loaded questions will, they can be useful in some cases. For example, if you simply need a clear “yes” or “no,” a loaded question might introduce too much ambiguity to lead to the specific answer you need. A leading question will deliver the response you need, and you can still watch for signs of deception in your interviewee’s short reply.)

Avoid the Wrong Questions

Just as asking the right questions can make the System more effective, asking the wrong questions can hinder your ability to spot deception—usually because they give the interviewee more time to think of what they’ll say, or they funnel extra mental energy away from focusing on your interviewee’s response.

The authors give many examples of mistakes to avoid when asking questions, which primarily fall into four categories: repeating questions that prompt repetitive answers, negative questions, multipart questions, and ambiguous questions. Let’s examine each category.

Mistake #1: Repeating Questions That Prompt Repetitive Answers

The authors urge you to avoid repeating the same question in different ways or asking follow-up questions that glean no additional information. For example, if you ask, “Did you steal the watch?” and the interviewee answers, “No,” a follow-up question like, “Are you sure?” would lead to useless repetition.

Recall that the more someone repeats a lie, the less mental effort they must spend to repeat it and stick to the story—by asking the same questions and getting the same responses, you’re helping your interviewee solidify their story.

(Shortform note: Interrogation experts suggest another risk of repeating your questions: You can confuse an honest interviewee. Repeating a question that the interviewee already answered may send the unintended signal that his previous answer was wrong in some way. If he initially gave what he believed to be an honest answer, your signaled doubt can lead him to feel unsure of his own memory. He may then try to “correct” his response to align with the facts he thinks you’re revealing to him.)

Mistake #2: Asking Negative Questions

Negative questions require a “no” as confirmation. Negative questions usually give the interviewee more time and mental bandwidth to strategize, as they take you more time to ask than positive questions, and they only require simple answers. For example, the negative question, “You didn’t steal the watch, did you?” takes more time to ask than “Who stole the watch?”

Mistake #3: Asking Multipart Questions

Multipart questions ask multiple questions at once, attempting to get multiple pieces of information in a single response—for example, “Were you at the store yesterday, and did you see anyone suspicious?” The authors say asking a multipart question is ineffective: Since there are so many questions packed together, seeing a sign of deception in your interviewee’s response won’t reveal helpful information—since you won’t know which part of your question was the trigger.

Mistake #4: Asking Ambiguous Questions

Ambiguous questions can be interpreted multiple ways and are easily misunderstood. For example, a question like, “Did you see what happened on Friday?” can be misleading if multiple notable events happened that day. The interviewee’s answer may refer to a different event than the one you’re referring to—thereby conflicting with your understanding of the truth.

The authors say if you can’t be sure your interviewee understood your question, you can’t be sure whether issues in their response are due to confusion or to deception. You’ll have to take additional time to clarify the interviewee’s intent, wasting time and mental energy.

(Shortform note: Multipart, ambiguous, and negative questions share a factor beyond those the authors focus on: They all hurt your ability to communicate clearly with the interviewee. If you want to learn specific information about your interviewee, he must fully understand each question to be sure the response is relevant to your goal. However, this clarity isn’t always vital: If you simply want to learn something like whether a job applicant is trustworthy enough that she won’t lie during an interview, but you see signs of deception, then her reasons for lying don’t matter.)

Step 2: Listen and Watch For Signs of Deception

Following each question, you’ll apply the second part of the System: simultaneously watching and listening for verbal and behavioral signs of deception in your interviewee’s response. Recall that the first sign must happen within five seconds of your question, and that you’re looking for a cluster: two or more signs.

We’ll now cover the specific verbal and behavioral signs that the authors say to watch for, as well as how each sign can signal deception.

Verbal Signs of Deception

Verbal signs of deception are certain things the authors have found guilty people often say in response to questions—usually in a bid to buy time or manipulate you into liking them.

The authors provide four broad categories of verbal signs to look out for: “inappropriate” responses, failure or reluctance to answer, qualifier-heavy answers, and generally suspicious responses. There are numerous specific signs within each category that you’ll look for and count when identifying clusters. Let’s explore each category and its signs now.

Verbal Category 1: “Inappropriate” Responses

Inappropriate responses don’t make sense given the tone or subject of your conversation. The authors outline four types of inappropriate responses.

Inappropriate questions are ones the interviewee would be unlikely to ask if they were innocent—for example, “What evidence do you have against me?” An innocent interviewee would assume there’s no evidence against him, so he’d be unlikely to ask this question.

Inappropriate levels of politeness: If the interviewee becomes overly formal with you or offers you a compliment for seemingly no reason, he may be trying to be more likable. According to the authors, this is often intended to make you less confrontational and more likely to believe him.

Inappropriately high concern for minor events: For example, the interviewee shows outrage over a coworker’s dessert being stolen from the community fridge. This is often an attempt to portray himself as a righteous, innocent person.

Inappropriately low concern for major events: For example, the interviewee shows indifference or dismissiveness toward a coworker's murder. By doing this, the interviewee may be trying to convince you that a legitimate problem isn’t actually concerning. The authors describe this as an irrational, defensive effort to escape reality.

Keep In Mind That Appropriateness Is Subjective

While the System is intended to help you avoid human bias when looking for deception, judgments regarding appropriateness tend to be highly subjective—either because you and your interviewee are simply different people or because of cultural differences.

On an individual level, people are often bad at judging what kind of response a situation merits. For example, one study found that many people interpret an angry response to an accusation as a sign of guilt—even though anger is a much more common response if you’re innocent than if you’re guilty.

In addition, different cultures have unique ideas of what makes an appropriate response. For example, to the Pashtun people, an accusation of minor wrongdoing merits outrage that can justifiably escalate to bloodshed. On the other hand, in many Western countries, office workers are often expected to endure disrespectful teasing without taking offense. If you’re unfamiliar with your interviewee’s culture, consider that your judgments of appropriate behavior may not align with theirs.

Verbal Category 2: Failure or Reluctance to Answer

The authors explain that the interviewee may also try to avoid directly answering you. Let’s examine five strategies the interviewee may use to dodge your questioning.

Complaints about procedure: Comments such as, “This is taking forever!” or “Why are you even talking to me about this?” can seek to convince you that you’re wasting your time talking to the interviewee and should look elsewhere.

Selective memory or understanding: An interviewee’s claim not to understand a question or remember a past event may signal that they’re feigning ignorance. This may be an attempt to frustrate you or convince you to move on in the conversation.

(Shortform note: If the interviewee seems not to understand or remember the event, there may be an explanation other than deception, like a mental health condition affecting the interviewee’s memory. Studies suggest that Post-Traumatic Stress Disorder and depression can make people more vulnerable to false memories, and false memories can be so convincing that they lead people to confess to crimes they didn’t commit. If someone claims not to remember an event, don’t try to convince them that they actually do remember.)

Too-specific answers only give information related to part of your question—deliberately missing its objective. For example, if you ask a potential hire, “What’s your experience overcoming project management challenges?” and the interviewee says, “I’ve managed successful projects before,” you’re dealing with a too-specific answer. The interviewee may be focusing on the specific detail of his projects’ success to hide his poor track record in handling management challenges.

(Shortform note: Deciding how to proceed after a too-specific answer can be tricky—recall that the authors advise against repeating questions, as it gives the interviewee time to think. However, it’s possible that repetition is advantageous in some cases: For example, lawyers often repeat questions during cross-examination, not moving on until the interviewee gives a satisfactory answer. Your next move depends on your goal: If you’re simply trying to find out whether your interviewee is trying to deceive you, you can note their too-specific answer as a sign and move on. If you need information the interviewee is withholding, it may be more to your advantage to keep pushing for a complete answer.)

Repeating information: The authors explain that repetition with the intent to deceive can take two different forms:

1. The interviewee claims they've already answered your question, so they don't need to answer again. This may be an attempt to avoid the discomfort of directly lying again.
2. The interviewee repeats your question back to you. For example, they might respond to your question “Where were you last night?” with “Where was I last night? Let’s see…” The authors say this may be a strategy to buy time.

Nonanswers: When the interviewee starts his response with phrases unrelated to your question—such as, “Funny you should mention that,” or “Great question”—he may be buying time to think about his response.

Other Reasons for Failure or Reluctance to Answer

The authors focus on detecting deception rather than what to do after you think you’ve detected it. When failure or reluctance to answer leads you to suspect deception, your next steps and how you weigh the reluctance or failure may vary depending on your conversation goals—and the interviewee’s goals.

Nonanswers, complaints about procedure, and repetition of information may not signal deception if you’re not accusing the interviewee of guilt. The first can signal a desire to change the subject, which could have any number of causes. While the latter two indicate an attempt to buy time, it’s common to want more time to think in situations like a job interview without necessarily intending to deceive.

Verbal Category 3: Qualifier-Heavy Answers

Qualifier-heavy answers use language that makes a statement of facts sound more certain or less certain—depending on whether the interviewee’s objective is to emphasize their trustworthiness or keep their assertions vague.

Emphasizing trustworthiness: When the interviewee uses language like “to be honest” and “to tell the truth,” they try to make a statement appear more certain. This highlights their credibility and buys time for the interviewee to think.

(Shortform note: It’s worth noting that dishonestly isn’t the only reason people bolster their credibility with language like “to be honest.” Research suggests that people often use this language when they’re afraid their answer—regardless of its honesty—won’t satisfy the listener’s expectations. Therefore, even an innocent interviewee may use this language when suspected of wrongdoing.)

Making vague assertions: The authors say language like “more or less,” “basically,” or “by and large” tries to make a statement of fact less certain. This allows the interviewee to exclude important information to create a quasi-truthful response that doesn’t admit guilt.

(Shortform note: Some people may use vague assertions as a way of building rapport with you rather than to deceive you. Communication experts explain that tentative language—like “maybe” or “I think”—can signal a desire for connection or collaboration. This suggests that it’s important to consider alternative explanations for this type of language.)

Verbal Category 4: Generally Suspicious Responses

The authors explain that some types of responses are simply “suspicious.” Here, we’ll go over five types of responses the authors find generally suspicious and what each suggests about your interviewee’s intentions.

Short denials buried in long explanations: Remember that creating complete fabrications can be psychologically difficult. The authors say that because of this mental barrier, a long explanation with only a brief denial inside it can signify the interviewee’s discomfort with their denial. To cushion this discomfort, they add information that may have little to do with the denial itself.

(Shortform note: With only five seconds after your question to notice signs of deception, it may be difficult to notice a short denial within a longer explanation. Therefore, it might be easier to watch for a short denial followed by a long explanation.)

Inconsistent responses, which make a different statement of fact from a previous response, suggest the interviewee fabricated at least one of them.

Ambiguous denials are claims of innocence like, “I didn’t do anything wrong!” which don’t directly address your question. The authors explain this often signals a desire to avoid committing to an outright fabrication.

Aggressive or condescending responses are often an attempt to scare or annoy you into backing off your line of questioning.

(Shortform note: Deception may not be the only reason behind inconsistent, ambiguous, or aggressive responses. For example, inconsistent responses may stem from the interviewee’s faulty memory, or she may give an ambiguous or aggressive response simply because she’s in a bad mood or doesn’t enjoy being questioned.)

Making oaths: The authors say an interviewee who swears on God may be both trying to look pious and hoping you’ll accept their earnestness.

(Shortform note: While the authors focus on religious oaths, people commonly swear on other important concepts, like the lives of their parents or children. These different oath types are similarly weighty: Those who swear on religious figures communicate their willingness to accept divine punishment if they break their oath, while those who swear on a loved one’s life communicate their willingness to stake that life on their word.)

Behavioral Signs of Deception

Alongside verbal signs of deception, the authors suggest watching for behavioral signs: things people do in response to your questions. These include: pauses before answering, suspicious body language, and disconnects between speech and action. As with verbal signs, we can divide these behavioral categories into subcategories, each of which counts as one sign of deception. Let’s cover each category now.

Behavioral Category 1: Pauses Before Answering

People commonly pause before answering a question. According to the authors, you must decide within the context of the conversation whether a pause is “too long.”

Some questions merit a pause—for example, “Where were you a month ago?”—because most people can’t remember details off the top of their head. Meanwhile, a question like, “Did you steal that gun?” warrants an immediate answer, because no honest person would need to think about the response.

As a caveat to this, the authors do suggest keeping in mind that some people naturally take longer than others to respond.

(Shortform note: The authors’ advice on determining how long a pause “should” be is fairly general, so you must rely on your subjective judgment here. However, this may open you up to the risk of bias because people tend to assume that even a brief pause indicates deception. One study suggests that just a two-second delay before answering can make interviewees seem less honest.)

Behavioral Category 2: Suspicious Body Language

Body language often subconsciously betrays someone’s true emotions by flagging sudden increases in anxiety. In the authors’ experience, the following kinds of body language reliably serve this purpose. We’ll explain each one, as well as any caveats you should keep in mind.

Shifting in place: The more pronounced the movement and the closer it occurs to your question, the more suspicious it is. The authors say it’s important to pay attention to when the movement happens: If the interviewee slides his chair forward for the first time immediately after your question, it suggests deception. On the other hand, if he slides around consistently, not as a response to your question, it may not be a sign of deception.

Throat clearing before answering, not after: Throat clearing signals both anxiety and an attempt to buy time. However, if it comes at the end of your interviewee’s response, it’s much more likely to be a natural bodily function.

Spikes in fidgeting or grooming often accompany anxiety. Examples include playing with hair, picking at fingernails, clicking a pen, clenching hands, and similar actions.

(Shortform note: Behaviors like throat-clearing and fidgeting can be signs of an underlying condition. For example, a vocal tic can cause excessive throat-clearing. Additionally, people with Attention Deficit Hyperactivity Disorder or Autistic Spectrum Disorder often fidget, and these motions can improve mental focus. In both cases, increased stress—such as the stress of being interviewed, not necessarily the stress of your question—can worsen the behavior. To get a better sense of whether to consider these behaviors suspicious, take some time to observe your interviewee before asking System questions.)

Hiding the face, especially the eyes or mouth, is a natural indication of shame or embarrassment—two emotions people commonly feel when lying.

(Shortform note: Hiding the face can have meanings other than deception, so don’t assume this sign always signals deception. For example, in Japan, it’s considered elegant for a woman to cover her mouth while laughing. More generally, blocking the eyes can signal disbelief or dissent—neither of which are inherently deceptive.)

Behavioral Category 3: Disconnects Between Speech and Action

The authors say the brain automatically matches verbal and behavioral actions to each other, and it’s difficult to act against this tendency. For example, an innocent interviewee should shake her head, not nod, when denying your accusation. On the other hand, nodding while saying, “I didn’t do it,” is a sign of deception.

This doesn’t apply to brief answers where any head motion could be punctuative, such as an emphatic nod alongside a simple, “No!” Additionally, the authors note that knowing your interviewee’s background is important: In some cultures, nodding means “no” while shaking your head means “yes.”

(Shortform note: Research suggests that, rather than the brain matching actions and words, actions can happen more quickly and instinctively than deliberately chosen words. For example, if someone hears an offensive joke, they may instinctively laugh, then apologize because they feel ashamed at laughing. Further research shows that people can train themselves to avoid their instinctive actions betraying their emotions, so don’t assume that immediate actions are always honest.