(Image: Danny Schwarz)
Does our capacity to lie change?
There are age-related differences in our ability to lie, and these are in line with the development of the prefrontal cortex – a part of the brain involved in controlling our behaviour. It doesn’t fully develop until young adulthood, after which it gradually declines. We predicted that the ability to lie would also follow this pattern and that’s what we found. We focus on the cognition of lying – how hard it is to lie, which we can judge by how long it takes a person to concoct a false statement. There’s a lot of evidence suggesting lying is more cognitively demanding than telling the truth.
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Isn’t there more to lying than being able to keep yourself from telling the truth?
Oh yes. Lying is a very complex phenomenon. There are many factors involved – the motivation to lie, emotions, social factors and so on. We focus on the cognitive aspect of lying. It’s a narrow scope, but that allows us to apply science to the issue.
How can you find out how frequently a person lies in everyday life?
We use a questionnaire. It sounds silly to ask people to tell us honestly how often they lie. But in another study we found that people who report lying a lot are also more likely to cheat in a separate task, so that gave us confidence in this approach.
How often do people lie?
The average is about two lies per day. What’s interesting is the age-related differences. Young children report lying on average 1.5 times a day, but that increases as they get older. By the time they’re adults, they lie nearly 3 times a day. Then lying frequency declines with age – seniors tell as few lies as young children.
Why do young adults lie more often?
I’m speculating, but it probably has something to do with gaining autonomy at that age – becoming an individual and separating themselves from their parents or teachers. They probably lie more to authority figures.
How can you apply what you are discovering?
We are mapping the conditions under which people find it hard to lie, so that we can exploit these conditions to develop lie-detection tests. You might need more advanced strategies for people in the adolescent to young-adult age range, for example. Young adults find it easier to lie, so we’d expect them to be more convincing.
How might you improve lie-detection tests?
We’ve been developing computerised tests where we try to see whether a person is lying or not, based on how fast they respond. Another cognitive approach might be to make lying more difficult. You could ask them to tell their story in reverse order, for example, or ask questions that they wouldn’t expect. For a long time, lie detection has focused on techniques that are based on stress. But these gave a lot of false positives, because truth-tellers can get as stressed as liars.
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is an associate professor of forensic psychology at the University of Amsterdam in the Netherlands, where he investigates how people lie and deceive. He is developing new techniques for lie detection
This article appeared in print under the headline “How our lies hit a peak”
