Can a 10-year-old be responsible for a crime? That's what brain research tells us

The age at which a child can be arrested, charged and detained in Australia is once again in the spotlight.

Last year, the Northern Territory became the first jurisdiction to raise the age of criminal responsibility from 10 to 12. Now the new, crime-tough government has promised to raise it back to 10. Previously, Victoria backed away from its earlier commitment to raise the age to 14, opting instead for 12.

But the UN Committee on the Rights of the Child believes that 14 years should be the absolute minimum. It has raised this age from its previous recommendation (2007) of 12 years, citing a decade of new research into child and adolescent development.

What does science say about this? What happens in the brain between the ages of ten and 14? And how well can children under 14 understand the consequences of their actions?

Who is a teenager?

Our research shows that adolescence is a critical period of development. During this time, children's experiences and discoveries shape the development of cognitive skills (including critical thinking and decision-making) and social and emotional skills (including moral judgment).

Adolescence also lasts longer than we think. Major brain developments begin in late childhood, around age eight to nine. Intense changes then follow in early adolescence (ages ten to 14). However, these changes continue well into the twenties, and full cognitive and emotional maturity is not usually achieved until around age 24.

However, everyone's brain matures at different rates. That is, there is no definitive age at which people reach “adult” cognitive maturity. What we do know is that early adolescence is crucial.

What effects does puberty have on the brain?

Puberty is a defining feature of early adolescence. Most of us are familiar with the changes that take place in the body and reproductive organs. But the rise in puberty hormones, such as testosterone and estrogen, also triggers changes in the brain. These hormones rise most sharply between the ages of ten and 15, although gradual changes continue into the early twenties.

Puberty hormones change the structures in the brain that process emotions, including the amygdala (which encodes fear and stress) and the ventral striatum (involved in reward and motivation).

This makes adolescents particularly sensitive to emotional rewards and threats. Our research has shown that the brain's sensitivity to emotions increases during early adolescence until around age 14 or 15.

At the same time, changes in puberty are associated with increased sensation seeking and impulsive behavior during early adolescence.

This connection is crucial when we talk about the behavior of children between the ages of ten and 14. The way their brains change during this time makes them more sensitive and receptive to emotions and they are more likely to seek out new and intense experiences.

How do young people make decisions?

The emotional context of adolescence influences how younger adolescents make decisions and understand their consequences.

Decision making relies on several basic cognitive functions, including the brain's flexibility, memory, and ability to control impulses.

These cognitive skills, which help us consider the consequences of our actions, develop most strongly between the ages of 10 and 14. By the age of 15, a child has typically achieved the ability to make complex decisions.

But adolescents at this age are still very sensitive to emotions. While their brains are capable of making complex decisions, their ability to think through consequences and weigh costs and benefits can be clouded by emotional situations.

For example, studies have shown that 13- to 14-year-olds were more distracted from completing a task and were less able to control their behavior when they looked at images that evoked negative emotions.

Teenagers' social world also has a significant impact on how they make decisions, especially in early adolescence. One study found that older adolescents (ages 15 to 18) are more influenced by the opinions of adults when weighing risks, while adolescents ages 12 to 14 are more influenced by other teenagers.

Experiments have also shown that adolescents ages 12 to 15 make riskier decisions when they are with peers than when they are alone. Their brain responses also suggest that they feel a greater sense of reward when they take these risks with peers.

How do teenagers understand the consequences of their actions?

The concept of criminal responsibility is based on a person's ability to understand his or her action and recognize whether it is wrong.

Moral reasoning—the way people think about right and wrong—depends on the ability to understand another person's mental state and take their perspective. These skills develop during adolescence.

Research suggests that compared to adults, adolescent brains have to put in more effort to process “social” emotions such as guilt and embarrassment. This also applies to moral judgments. These findings suggest that teen brains may have to work harder when considering other people's intentions and desires.

Young adolescents have the cognitive ability to recognize that they've made a bad decision, but this one is more mentally demanding. And social rewards, emotions, and the chance to experience something new all have a powerful influence on their decisions and actions in the moment – possibly more than whether it's right or wrong.

Early adolescence is crucial for the brain

There are also a number of reasons why adolescent brains may develop differently. These include various forms of neurological disabilities such as acquired brain injury, fetal alcohol syndrome, attention deficit hyperactivity disorder (ADHD) and intellectual disability, and trauma.

Adolescents with neurodevelopmental disorders are likely to cope differently with decision-making, social pressure, impulse control and risk assessment and face additional difficulties. They are disproportionately likely to be incarcerated worldwide.

In Australia, more Indigenous children and young people are incarcerated than their non-Indigenous peers.

Every child develops differently and some face special challenges. But for every person, the period between 10 and 14 years is crucial for the development of cognitive, social and emotional skills that will serve them for the rest of their lives.