Nonverbal vs. Verbal Deception Detection?

Originally posted on Humintell’s website May 2, 2018 (https://www.humintell.com/2018/05/nonverbal-vs-verbal-deception-detection/)

Is deception detection easier when we have verbal cues? Could it even be harder?

A lot of sensory input goes into our ability to detect deception, but it is hard to tease out the role of verbal and nonverbal cues. We train you to look for both, but a new study seeks to break down the question and look at exactly what helps us determine whether somebody is lying.

This research combines expertise in communications and criminology by creating an experiment where participants are exposed to an interrogation record and tasked with evaluating whether the interviewee is lying. This is varied between multiple cases where participants get a full videotape, an audio clip, or just a transcript.

This builds on research finding that we rely on mental shortcuts in order to more effectively detect deception. The study authors broke down biases into truth, visual, demeanor, and expectancy violation biases.

Each of these is relevant. For instance, truth bias leads us to assume truthfulness in others, while expectancy violation bias general sees unusual behavior as constituting a lie. Perhaps more relevant to the question at hand, visual bias emphasizes visual stimuli in detecting deception, while demeanor bias sees certain communication styles as credible ones, regardless of the truth.

Unfortunately, none of these biases are necessarily accurate measures of deception detection. In fact, one of our past blogs has pointed out that the common belief that people fail to make eye contact when lying is a myth, showing how our expectancy violation biases create problems.

By exposing participants to different levels of verbal and visual cues, the study authors sought to explore each of these biases. While past research has explored similar topics, it tends to have focused on short, less than one minute clips. This prevents an understanding as to whether interviewers can use a longer exposure to better understand deceptive behavior.

Essentially, this experiment hypothesized that the more nonverbal cues available, the more likely the participants would assess the interviewer as truthful, with the full videotape exemplifying this tendency.

Interestingly, deceivers were generally believed the most when participants had access to the audio and visual components of the interview, but this was not the case for those telling the truth. Instead, perceptions of truthfulness peaked with access to audio but began to decline when visual components were involved.

The researchers saw this as broadly confirming the important role of cognitive bias. For instance, deceivers likely paid closer attention to their demeanor (in order to hide their lie), resulting in truth-tellers being likely to showcase more unusual behavior and thus introducing the demeanor bias.

The real lesson here is that our cognitive biases may mislead us, but that doesn’t mean that heuristics are all bad news. Instead, empirical science has developed a more valid framework to rely on.

And it is that sort of framework that Humintell regularly trains people in. One great way to learn empirically-validated lie detection is to get trained in our expert techniques.