It’s rare for young children to kill. But there are exceptions. Last October, an 8-year-old boy in Alabama strangled a toddler to death. That same month, an 11-year-old in Tennessee shot and killed another child after an argument over puppies.
Between 1980 and 2008, children under age 14 made just up 0.5% of homicide offenders, according to data (pdf) from the US Department of Justice. When children do take the lives of others, society must face a question no one wants to confront: At what age can children be held responsible for their actions?
Countries around the world vary widely in their answers. In England and Australia, the minimum age is 10. In Belgium, the bar is set at age 18. The United States allows its states to decide, which means children can face criminal charges at a wide variety of different ages, ranging from seven (Oklahoma) to 15 years (New Mexico). The law tends to consider children’s competence to stand trial and their ability to make decisions when setting minimum ages. But it often overlooks scientific research in defining these limits.
Now science is weighing in on the question. Kay Bussey, a developmental psychologist at Macquarie University in Australia, decided to investigate the issue after coming across the case of a 10-year-old boy in Australia who threw his friend into a river in 1998, causing him to drown to death.
“A debate arose about whether he was responsible,” Bussey tells Quartz. “ [The judge] didn’t hold the child responsible for the conduct because he argued the child couldn’t differentiate [the crime] from everyday childish mischief.”
Bussey and her student Paul Wagland decided to assess children’s ability to understand intent and self-regulate their own behavior—two main components involved in defining criminal behavior. Their study, recently published in Legal and Criminological Psychology, examined 132 men and women from four age groups (ages eight, 12, 16, and adults). They presented participants with a series of short stories. Some described criminal acts, including assault, theft and arson. Other vignettes described mischievous versions of similar acts that did not violate the rights of others or put people in danger.
The study found that 8-year-olds were just as likely as older participants to rate criminal acts as “more morally bad” than mischievous ones. They were able to anticipate that criminal acts would make them feel worse about themselves, make their peers view them more negatively, and result in more severe punishments. According to the study authors, the ability to understand these potential consequences is important for regulating behavior.
This suggests that children as young as eight are able to understand what constitutes criminal conduct and control their behavior accordingly. But there are factors in the study that merit a closer look, according to some researchers who feel the study overlooks an important issue.
“This study utilizes a clever design to investigate the age at which children and adolescents seem to appreciate the ‘wrongfulness’ of criminal behavior,” David Fassler, a professor who specializes in child and adolescent psychiatry at the University of Vermont and was not involved in the study, tells Quartz. “However, the authors overreach in their interpretation of ‘the ability to self-regulate’ behavior with respect to potential criminal conduct.”
According to Fassler, the study’s measures of cognitive capacity overlook recent evidence from studies that show children’s brains continue to develop through adolescence and early adulthood. This could impact young people’s ability to behave in line with societal expectations.
“The research we’ve done through the MacArthur Network demonstrated that aspects of executive functioning that include self-regulation are changing and improving to age 30 and beyond,” says Jennifer Woolard, a developmental psychologist at Georgetown University who was not involved in the study. “And we know the structural and functional development of the brain continues well into the twenties.”
Importantly, the prefrontal cortex, which is involved higher-level functions such as decision-making and impulse control, is one of the last brain areas to mature. This research suggests that while young children may be able to appreciate the subtle differences between criminal and mischievous acts, and even anticipate the consequences of that behavior, they may have a more difficult time holding back their reactions. As such, scientists and juvenile justice advocates in the US and the UK have recently called for an increase in the age of criminal responsibility to account for this difference in young brains.
The fact that children lack the levels of cognitive control that adults possess may also make children more likely to be rehabilitated. Policy makers in the US have recently made some changes in recognition of this fact. In 2012, the US Supreme Court ruled that sentencing juveniles to mandatory life sentences was unconstitutional. The Court extended the ruling this January, offering a second chance to individuals currently serving mandatory life sentences for crimes they committed as children.
Yet while research suggests that children and young adults do not possess the same mental capacity as adults, US children who commit serious crimes can experience very different outcomes depending on where they live. The 11-year-old Tennessee boy was charged with first-degree murder and sentenced to juvenile prison until his 19th birthday. Meanwhile, Alabama state law does not allow criminal charges against 8-year-olds, so the child was accused of juvenile delinquency instead.
Bussey herself warns that the fact that children are able to distinguish between right and wrong doesn’t mean that they should be treated as adults. For one thing, because young people are more amenable to change, greater efforts should be made to help them reform. Bussey also points to the importance considering of social factors that may affect children’s behavior, including peer pressure and parenting.
“At this point, I can’t say anything conclusive, except that it’s very clear that children do have the capacity for self-regulation—they do self-reflect and realize that they are going to feel remorseful,” Bussey says. “The point that I would like to argue in terms of policy [is that], yes, children do have the capacity to judge right and wrong, therefore should be held responsible, but you need to be very careful in how you are going to administer that.”