How to Baseline Someone’s Behavior Like an FBI Agent

What does someone look like when they’re lying? If only there was an easy, one-size-fits-all answer to this question. The truth is, every liar is different. Fortunately, there are numerous facial expressions, body language and speech patterns that researchers and investigators have linked to deception. Definitive patterns exist.

The key to using these nonverbal and verbal cues is to compare them with someone’s normal behavior—their baseline. This word may be new to you, but the concept won’t be. We do it subconsciously all the time. Learn to baseline so if the time comes to evaluate someone’s truthfulness, you have something to compare against.

Professional investigators like FBI agents, detectives, and other law enforcement personnel rely on baselining as a core tool for reading people. Separating ordinary stress from meaningful shifts in behavior may signal deception. If you’ve ever wondered how people catch the liar on hit shows like The Traitors, it often comes down to baselining what “normal” looks like and then spotting clusters of subtle changes when the pressure hits. To spot deception like a secret agent, start by building a baseline first and then look for clusters of changes in their verbal and nonverbal behavior.

Key Takeaways

Baselining means understanding someone’s normal speech patterns, body language, and behavior so you have a reliable point of comparison.
There is no single sign of deception. Effective lie detection analyzes clusters of behavior.
The most important baseline observations often begin in the first moments of interaction.
Asking varied questions helps reveal natural reactions that establish a clearer behavioral baseline.

Baselining in lie detection grew out of real-world interview and interrogation practice long before it became a popular word. One early ancestor shows up in WWII’s programs, where detainees were monitored continuously; information was gathered across everyday conversation and formal questioning, and dossiers were updated as analysts learned each person’s “normal” patterns over time.That postwar experience fed decades of U.S. research and training on interrogation.

Later, modern police and investigative training formalized the idea as “behavioral baseline” building, using early rapport and small talk to observe an interviewee’s typical patterns.

Researchers like Aldert Vrij note that this is exactly why baselining became so appealing, but also why it can go wrong if you compare low-stakes small talk to high-stakes accusations.

Baselining Basics

What is a Baseline and How Do You Start Baselining?

Begin baselining with the very first handshake. We don’t get a second chance to make a first impression, and we don’t get a second chance to observe a first impression either. The first moments when we meet someone new present the best opportunity for forming a baseline of their behavior. A skilled interviewer or salesperson will instantly begin sizing up potential hires or customers, beginning with—or even before—the first handshake. Sally in HR or Steve, the sales guy, have already begun evaluating whether a hire or a deal is going to happen, by observing posture, gaze, and vocal quality from the first handshake. We all can and should be doing this, both in business and social situations, making mental notes of people’s gestures and reactions and listening more carefully all the time.

There is nothing invasive about carefully observing the people with whom we’re talking. We collect this information subconsciously already; the leap here is to make it a more conscious effort so we don’t forget it all once we leave the room. Baselining is nothing more than collecting useful details about how a person normally reacts under normal conditions to small talk, personal questions, and jokes. It should be part of every meet-and-greet we do—with business associates, clients, neighbors, and friends.

What Questions Help Reveal Body Language and Speech Patterns?

Ask a series of questions to elicit different reactions. Baselining is most useful when we can gather a person’s reactions to a few different situations. But not every setting will expose the full range of behaviors for us to baseline. Meeting someone at a funeral, for example, means we probably won’t be gauging how they react to jokes. Yet in many cases we can steer a conversation to elicit the sort of reactions we want to note.

We can offer a genuine compliment, say something surprising, or politely challenge a person’s opinion to trigger a reaction that we can observe and file away. Did Emma blush and look down to the left after the compliment? Did Damon visibly bristle and clench his fist when he was challenged? The verbal and nonverbal behavior we observe in nonthreatening circumstances will inform our future lie detection efforts.

When baselining, you’re looking to capture their normal vocal tone and speed, standing and seated posture, nervous tics, style of laugh, use of hand gestures, and how they express emotions of surprise and excitement.

How Do You Remember Someone’s Baseline Over Time?

Keep a record of the baseline behavior in your head. Writing down the details of a person’s baseline may sound a tad excessive – and it is. Who do you think you are, anyway? … Colombo? The lady on Murder, She Wrote?

Remembering someone’s baseline details, however, is crucial to any future lie detection you may need to do. So you do want to file away the baseline information you observe at every meeting. Short of building a behavior dossier on all your coworkers, neighbors, and friends, what can you do?

The answer is simple: When you meet someone for the first time, mentally file their baseline behavior with the record you make of their name and other vital stats: job title, hometown, spouse, number of kids, and so on. Even if you’re not good with names—and most of us are not without practicing at it—the conscious effort to gather and store the extra baseline info will give you additional vivid details by which to remember a person.Want to know what your own baseline looks like? Ask your spouse or a trusted friend to tell you what your default expressions and body language look like. The information may help you become a more effective communicator. Want to know what your own baseline looks like? Ask your spouse or a trusted friend to tell you what your default expressions, body language, and speech patterns look like. The information may help you become a more effective communicator. Pamela Meyer’s courses can also teach you the necessary skills to baseline anyone’s behavior.

Frequently Asked Questions

What is a baseline?

A baseline is a clear understanding of someone’s normal behavior that gives you a reliable point of comparison when evaluating changes in their verbal and nonverbal communication. In deception detection and behavioral observation, baselining means identifying how a person typically speaks, moves, reacts emotionally, and expresses themselves during ordinary, low pressure interactions.

Researchers and professional investigators use behavioral baselines because there is no single sign that proves someone is lying or acting differently. Instead, you compare current behavior against what is normal for that individual and look for clusters of meaningful shifts. Early interactions, including the first handshake or moments of small talk, often provide the best opportunity to observe posture, gaze, vocal tone, gestures, and natural reactions.

How do you baseline someone’s behavior?

To baseline someone’s behavior, you observe how they normally speak, move, and react under ordinary, low pressure conditions so you have a reliable point of comparison later. Baselining means identifying a person’s typical speech patterns, body language, vocal tone, posture, gestures, and emotional expressions before any high stakes conversation begins.

Start in the first moments of interaction. The initial handshake, eye contact, posture, and vocal quality provide valuable information about what “normal” looks like for that individual. Skilled interviewers begin forming a behavioral baseline immediately, often during small talk or early rapport building.

Next, ask varied questions that elicit different natural reactions. Offer a compliment, introduce something mildly surprising, or politely challenge an opinion. These nonthreatening exchanges help you observe normal reactions to social and emotional cues. Over time, mentally store these observations alongside basic personal details so you can later compare meaningful shifts in verbal and nonverbal behavior.

When should I start baselining someone's behavior?

You should start baselining someone’s behavior from the very first moments of interaction, often beginning with or even before the first handshake. Early observations provide the clearest view of a person’s normal speech patterns, body language, posture, gaze, and vocal quality before pressure or high stakes topics influence behavior.

Professional investigators and trained interviewers use initial small talk and rapport building to observe how someone naturally reacts under ordinary conditions. These low pressure exchanges help establish a reliable behavioral baseline that can later be compared against clusters of changes in verbal and nonverbal behavior. Baselining should become part of everyday meet and greet situations, whether in business conversations, interviews, or social settings.