How to be a human lie detector.

Several years ago, my friend Jack, who’s an FBI agent, described himself as a ‘human polygraph.’ When I asked him how he did it, he said, “there’s no magic. I just pretend I have a terrible memory.”

It’s easy to over-focus on getting truthful responses from research participants. Not to say that truth isn’t important, but it’s good to remember that sometimes it’s valuable to let people lie to you. When they provide dishonest answers to your questions – whether deliberately or unintentionally – instead of describing the world as it is, they’re describing the world as they would like it to be, or telling you how they would like to see themselves.

This is particularly valuable learning when dealing with sensitive topics. People can be reluctant to tell you how they really feel about things, and instead tell you what they think you want to hear or what they think is socially acceptable. In other words, they’re providing clues about what embarrasses them, or compromises their self-esteem, or makes them uncomfortable. This can be key to uncovering hidden motivations.

So, when conducting research and analyzing your data, it’s important to be able to distinguish truth from falsehood. Over the course of my career, I’ve identified three invaluable techniques to tell if research participants are being honest. To be clear, these methods aren’t perfect, but I’ve found them to be pretty reliable

1)  Ask the same question repeatedly.

This is the one I learned from G-Man Jack. To determine how truthful an answer is, ask the question multiple times and in a variety of ways. When people are telling the truth, they have no difficulty sticking to their story. But when they’re dissembling, their replies can be inconsistent, and the story tends to wander closer to the truth the more you press them.

Sometimes I’ll ask the question exactly as I asked it in the past, sometimes slightly differently. Such as:

• Why do you use Tide?

• What are your reasons for using Tide?

• Why do you think so many people use Tide?

• Why don’t you use Gain?

• Why do you love Tide?

• What is the best thing about Tide?

• What are three things you like about Tide?

• How would you describe people who love Tide?

• What do Gain users not understand about Tide?

• What don’t you like about Gain?

• How do users of Tide differ from users of Gain?

• And so forth. (I can do this all day.)

Don’t be uncomfortable asking a question multiple times. If a participant calls you on it, own up … “yup – you caught me!’” Then explain that asking a question multiple times is a common research practice.

Pro-tip: Put your question variations in your moderator’s guide. It’s also a good idea to manage the expectations of your client: make sure they know that you’re going to use this probing tactic. Otherwise, they might think you’re not paying attention to the participants’ answers.

2) Pretend to forget.

Deliberately misremember what respondents have told you earlier in the conversation. This gives them the opportunity to correct you.

“You mentioned earlier that you don’t care for Tide. Does that mean you prefer Gain?”

If the participant doesn’t correct you, you just learned something. If they do, apologize and ask them to remind you of their previous answer, and see how closely this answer matches the earlier one.

3) Biometrics

A few years ago, I was conducting research among endocrinologists, exploring the idea of active patient involvement in treatment decisions. When we showed the doctors concepts for tools to increase patient participation, nearly all said they were highly interested in the idea.

However, we didn’t just have to take their word for it. We were also capturing biometric data during the interview. Specifically, galvanic skin response and facial coding. For some of the participants, the GSR showed a surprisingly strong physiological responses to the descriptions, and the facial coding showed a stew of negative emotions—specifically anger, fear and contempt. So the biometric data was in stark contrast to what those participants were saying. The big insight: while some doctors might dislike the idea of patient involvement in medical decisions, they may not feel it’s socially acceptable to say so. This led the client to take a decidedly different approach to marketing the patient involvement tools.

One additional thought—you can use these techniques in your personal life as well. Significant others particularly enjoy being questioned this way.  And your kids will love it too, although they might resist being wired up to biometric equipment.

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