LONDON — Laughter may be contagious for most of us, but a new study finds boys who don’t feel compelled to giggle when their peers do are more likely to later become psychopaths.

Researchers at University College London in the UK recruited 92 boys aged 11 to 16 for a study on how social reactions as an adolescent could predict later behavior. About two-thirds of the participants had been diagnosed with disruptive behaviors or callous and unemotional (CU) traits.

It should be noted that CU traits and disruptive behavior have been previously linked to an increased risk of developing psychopathy.

For their experiment, the researchers used fMRI scans to measure the brain activity of participants, all of whom were exposed to sounds of both fake and real laughter, occasionally interspersed with crying.

While listening to these noises, participants were asked to rate on a seven-point scale the degree to which they believed the laughs they heard were genuine, along with the extent to which they were emotionally affected.

Adolescents who demonstrated both risk factors for psychopathy reported less of an urge to laugh in conjunction with others than those who were believed to have one or neither.

This finding was supported by the results of the fMRI scans, which showed reduced brain activity in regions associated with emotional reasoning.

While “it is not appropriate to label children psychopaths,” as psychopathy is a personality disorder experienced by adults, the signs can be detected at an early age, according to senior author Essi Viding.

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Future research can explore whether other friendly social cues, such as smiling, words of encouragement, and displays of love, also prompt a lackluster emotion response from those at risk for psychopathy.

Ultimately, these at-risk adolescents may simply experience life differently than the rest of us, Viding suggests.

“Those social cues that automatically give us pleasure or alert us to someone’s distress do not register in the same way for these children,” she says in a press release. “That does not mean that these children are destined to become antisocial or dangerous; rather, these findings shed new light on why they often make different choices from their peers.”

“We are only now beginning to develop an understanding of how the processes underlying prosocial behavior might differ in these children,” she continues. “Such understanding is essential if we are to improve current approaches to treatment for affected children and their families who need our help and support.”

The full study was published last month in the journal Current Biology.

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