The Liar Is in the Details: A New Way to Detect Deception

Deception is an exceptionally common feature of communication, yet the ability to detect it remains elusive. Researchers continue to seek new methods that could separate the honest from the dishonest, but the challenge remains. You may follow this literature from time to time, hoping that some new glimmer of hope will emerge to help guide your own detection skills. However, you may be ready to give up and figure the only tool you have is your own gut feeling.

Perhaps you have a longtime friend who moved away years ago but promised, several weeks ago, to visit with you while traveling near where you live. You rearranged your schedule, invited family members to join for the occasion, and started to figure out a menu. Luckily, you didn't buy the food. A few days before the date, the friend calls and turns the entire plan upside down. Rather than come to your home, how about if you drive for 2 hours to meet them for an overnight visit to a hotel: “Wouldn’t that be so much fun?” As explanation, the friend provides a lengthy and rambling story about why they can’t come to see you, including something about a job that fell through, but something about this doesn’t seem right. Should you believe them or not?

The 4 Maxims of Communication and What Happens in Deception

As summarized by Sam Houston State University’s Daniella Cash and colleagues (2024), nonverbal cues have their limitations in spotting a liar, even though many people believe them to be most accurate. This is good news in your case, where that channel of communication is blocked off anyhow since all of this took place by phone and text. It is, as Cash et al. maintain, the verbal channel that is your best bet.

Breaking this down further, the Sam Houston U. researchers point to two of what are considered the four “Gricean” maxims of effective communication, which are principles developed by the linguist Paul Grice. The set of four includes quantity (length), quality (truthfulness), relation (relevance), and manner (clarity). Cash et al. believe that it’s quantity and relation that could ultimately pave the way for a new understanding of deception. As they note, “When liars attempt to deceive, they may violate one or more of these conversational norms and arouse suspicion pertaining to the veracity of their account.” In other words, maybe you can tell a lie if an explanation is too long and full of useless detail.

The Length and Relevance of Lies

To test the proposal that a simple length-relevance formula could work to unpack a lie, Cash and her coauthors designed two experiments presenting undergraduate participants with the job of rating the truthfulness of five statements in which a student (at another school) potentially lied about turning in a homework assignment. The wording of the lies was based on actual excuses the first author received from her students. See which seem most believable to you:

• Baseline: I did the homework.
• Related-few: It covered the stuff from Tuesday.
• Related-many: It took me 3 hours to answer all of the questions. The first three questions took up an hour and a half and covered the information we talked about on Monday
• Unrelated-few: I enjoy this class.
• Unrelated-many: The information we cover in this class is easy to understand, and I like the material. I put a lot of time into the course and the graded work.

The findings from the first experiment suggested that, compared to baseline, longer statements seemed more believable whether or not the details were relevant unless, as in the second experiment, students were forewarned to focus on the relevance of the longer excuses. This advance notice helped somewhat. Overall, though, in contrast to the Gricean maxims, the ratings of truthfulness showed length trumps brevity even when that length contains irrelevant details. The short and sweet base statements were judged as deceptive, and the many (related or unrelated) as truthful. Even worse, “people are unable to accurately report their cognitive processes.” In the condition when they were warned to pay attention to relevance, the students failed to realize just how much they let verbosity rather than relevance sway their judgments.

Using the Gricean Maxims to Your Benefit

Now that you know how easy it is to be deceived by a heap of unnecessary details, you can put your own relevance-judging tools to the test. Think back on what that friend told you. Even though it may have amounted to 10 minutes of verbiage, did any of it have to do with their ability/inability to actually drive to your home? Why would their job have anything to do with it if, in fact, they really wanted to see you and catch up with your family?

What is perhaps most impressive about the Cash et al. study is that it was based on students rating other students. It’s the rare student, one might argue, who doesn’t come up with some type of bending of the truth when turning in a late assignment. Transportation troubles, computer glitches, and all types of personal reasons can come up as reasons for late work. The students in the Sam Houston U. study, one would expect, would be attuned to the unrelated-many statements, but, still, they got taken in by the shaggy dog story of the liar.

Deception Essential Reads

What Happens When You Keep Secrets?

What It Means to Be Truthfully Misleading

To sum up, sorting out the relevant from irrelevant takes time when you’re trying to get to the truth. Rather than tune out to an overly long set of lies, zone in on the most pertinent, and you’ll maximize your chances of getting to the pathway of honest communication.