Young adults – defined here as people aged 18 to 29 – are the most skilled liars, while teens are the most prolific. That’s according to a new study published in Acta Psychologica that claims to be the first ever to investigate lying behaviour across the entire lifespan.

The research involved members of the public who were visitors at the Science Centre NEMO in Amsterdam. In all, 1005 people took part, aged from 6 to 77. To test lying ability, Evelyne Debey and her colleagues presented the participants with simple general knowledge questions (e.g. “Can pigs fly?”). These questions had to be answered as quickly as possible, either truthfully or dishonestly, depending on the colour of the YES/NO response options. Taking the pig question as an example, the idea is that a skilled liar ought to be able to answer “yes” very quickly, whereas a poor liar will be delayed when answering dishonestly, or they might even give a reflex honest answer.

Young adults showed the fastest reaction times and lowest error rates on this test of lying. Overall, lying proficiency showed an inverted U-shaped curve through the lifespan, improving through childhood, peaking in young adulthood and then gradually declining into old age. This meant that lying proficiency was the same in the youngest children (aged 6 to 8) as it was in the eldest participants (aged 60 plus).

To measure lying frequency, the researchers asked their participants to report the number of lies they had told during the preceding 24 hours to different people in different situations (e.g. to a stranger or relative; face to face or online), and to describe those lies. Overall, the participants reported telling an average of two lies during that time, which is consistent with past research. Teens admitted to telling more lies (an average of 2.8) than any of the other age groups. Again there was an inverted U-shaped relationship between age and lying such that lying frequency increased during childhood, peaked in adolescence, then decreased through life, so that the oldest group lied with the same frequency as the youngest participants.

The researchers have a theory that the reason lying skill and frequency show this pattern through the lifespan is because of age-related changes in inhibitory control – the idea being that to lie successfully you need to be able suppress the truth, and that young adults have the most inhibitory control.

To test this, the researchers had the same participants complete what’s known as a “stop-signal task” – this involved pressing a button to indicate as fast as possible whether an X or an O had appeared on-screen. Crucially, on 25 per cent of these trials a tone sounded that told them to cancel their response. The later this tone sounded, the harder it is to withhold a response. Participants with greater inhibitory control can usually cancel their response even when the stop signal is given very late.

The participants’ ability on this stop-signal task increased through childhood and peaked in young adulthood. However, performance after this age remained relatively stable. Moreover, performance on the stop-signal task did not correlate strongly with lying proficiency. This appears to undermine the researchers’ theory about inhibitory control, but they argued that there are different types of inhibitory control and that perhaps a different measure of a different kind of inhibition (such as the Stroop Test, which measures the ability to deal with interfering mental demands) would have correlated more strongly with lying ability.

In a field that so often relies on student research participants, this study stands out for its involvement of the general public across wide range of ages. However, as the researchers acknowledge, the findings come with many caveats. Among these is the fact the study was cross-sectional – it doesn’t tell us anything about how the same people’s propensity for, and ability to, lie changes as they age. Also, the test of lying ability was artificial and involved none of the emotional consequences of real-life lies. Note too that, as shown in past research, lying frequency was highly skewed so that half the participants reported telling no lies in the previous 24 hours, and over 50 per cent of the lies were told by prolific liars who made up just 9 per cent of the sample.

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Debey, E., De Schryver, M., Logan, G., Suchotzki, K., & Verschuere, B. (2015). From junior to senior Pinocchio: A cross-sectional lifespan investigation of deception Acta Psychologica, 160, 58-68 DOI: 10.1016/j.actpsy.2015.06.007

Christian Jarrett (@Psych_Writer) is Editor of BPS Research Digest

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