Boys who don't catch the giggles could be at a higher risk of becoming psychopaths — here's why

Laughter is contagious — it's hard not to join in when you hear it. It also feels good to laugh, and research has shown it helps with bonding and peacekeeping between people. It can also boost your health.

However, laughter doesn't have the same impact on everyone. For example, those with Dark Tetrad personality traits — narcissism, sadism, Machiavellianism, and psychopathy — do not approach social cues like laughing like the rest of us.

Relationships with these people don't progress in a regular way, as they only see their connections with people as transactional. This means they are only interested in having interactions with people when they can see themslves getting some kind of benefit, and thus have little or no concern for the wellbeing of others.

New research, published in the journal Current Biology, showed that young boys could be at a higher risk of developing psychopathy in adulthood if they don't have the same urge to join in with laughter as others.

The scientists from University College London recruited a control group of 30 normally-behaved boys as well as 62 boys aged 11 to 16 with disruptive behaviours — with or without callous, unemotional traits. Each boy's brain was scanned using functional MRI.

The researchers then measured the childrens' brain activity when they listened to genuine laughter, posed laughter, and crying sounds, and asked the boys to rate on a scale of one to seven their answers to questions such as: "How much does hearing the sound make you feel like joining in and/or feeling the emotion?" and "How much does the sound reflect a genuinely felt emotion?"

The boys who showed disruptive behaviour and who had high levels of callous unemotional traits — who were thus at higher risk of becoming psychopathic — were less interested in joining in with laughter than those who didn't show the traits or were normally behaved.

All the subjects' brains reacted to genuine laughter, including in the audiroy cortex, which is where sounds are processed. However, there were also differences between the groups. The callous, disruptive boys had reduced brain activity in areas called the anterior insula and supplementary motor area, which are thought to be involved in being in tune with other people's emotions.

The disruptive but un-callous boys showed some differences to the normally behaved boys, but they weren't as pronounced.

Essi Viding, senior author of the study and Professor of Developmental Psychopathology at UCL, said in a statement that it is not appropriate to label children as psychopaths, as it is an adult personality disorder. However, she also said previous research has shown certain children are at a higher risk for developing psychopathy, and the team screened for those who indicated this risk.

"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," Viding said.

"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 behaviour might differ in these children. 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."

Now, the researchers want to look into whether these children also respond differently to smiling faces, words of encouragement, or displays of affection. They are also interested in the age where these differences arise.