Friends of the Nonverbal Communication Blog, this week we present the paper “Atypical behaviors found in some mental health conditions negatively affect judgements of deception and credibility” by Lim, A.; Young, R. L. and Brewer, N. (2022), in which authors carry out a study to examine some visible behaviors that we associate with an unbelievable speech, but also, are behaviors that people with some mental conditions can present.
There is a general belief that what people say does not matter as much as their behavior when they say it, since it could indicate guilt, deception, regret…, etc.
In a 2006 study, 58 participants were asked when they knew someone was lying. The most common answers were: when there is an aversion to the gaze, incoherence, exaggerated body movements, certain facial expressions…
Only one of the elements was related to the content of the message: the inconsistency. Which leads us to think that we focus much more on non-verbal elements than on verbal ones, an idea consistent with numerous previous studies on the subject.
While the use of unreliable cues in lie detection is concerning in itself, it is likely to be problematic for people who have a disability or mental health condition as well.
For example, some people with social anxiety and social communication disorders have difficulty maintaining eye contact, which, rather than being a guilt avoidance mechanism, is more related to fear of social interaction.
On the other hand, repetitive body movements may be behaviors of people with neurodevelopmental disorders or autism spectrum disorders.
However, to an observer who doesn’t know much about the subject, these behaviors can be misinterpreted as signs of nervousness or guilt.
Another indicator of trustworthiness is emotional expressions. For example, there are studies that show that, in a trial, both victims and defendants are perceived as more credible when they show negative emotions (such as crying) rather than neutral (flat affect) or positive emotions (smiles).
Despite the fact that many studies have pointed out that it is necessary to pay attention to verbal signals especially, the stereotype that the most important are the non-verbal ones is very widespread, even for professionals such as police or judges.
This can be explained by attribution theory, which is based on the premise that individuals inherently seek to understand and explain observed behaviors, thus attributing a cause to the behavior.
In this study, authors examine the effect of four cues commonly associated with lying: gaze aversion, repetitive body movements, monologues, and flat affect. These behaviors are selected because they are associated with lying and also because they often appear in people with mental health problems.
It was hypothesized that individuals displaying these behaviors would be perceived as more liars and less credible.
The total sample was a total of 392 people of legal age, gathered through online tools.
They were shown a video of a game, in which one person had to choose whether or not to steal a small amount of money and then convince another person that they had or had not. If they got away with it, they got $50; if not, only 10$. The people in these videos were professional actors with a standardized script.
Results revealed significant effects of repetitive body movements and monologues on perceived deception, and significant effects of flat affect on credibility. It is important, as it could have important practical indications for people who often show these behaviors, for example, people with schizophrenia or mood disorders, people with neurodevelopmental disorders, autism spectrum, among others.
However, contrary to expectations, and also contrary to previous studies, gaze aversion did not have a significant effect on judgments of deception or credibility. It is possible that this happened because in this study this trait was studied individually, while in most studies it is interpreted within a context or accompanied by other behaviors that can give strength to the “lie effect”.
One limitation of the study is that it was not conducted with people with mental health conditions, so authors recommend the direct participation of these populations.
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