Longitudinal studies that follow a group of people from cradle to grave can provide valuable insight and change policy. And they just might confirm everything you thought about that kindergarten bully.
Moffitt had a PhD in clinical psychology with a focus on crime. She was keen to investigate teenage mayhem, but it was New Year’s Day and Dunedin’s streets were virtually empty.
“Everyone had gone camping and I could see milk bottles at people’s gates with money beside them. I thought ‘Oh, my goodness, this is a very trusting community. There’s going to be no juvenile crime high jinks here.’”
Even after spying a group of youths sniffing glue near the Octagon in the city centre, she wondered if moving to Dunedin had been a mistake. What, she wondered, could 1000 13-year-olds at the bottom of the world teach her – and, by extension, the rest of us – about juvenile crime?
Moffitt had come to work on the University of Otago’s Dunedin Multidisciplinary Health and Development Study, which has been following the lives of 1037 people born between April 1, 1972 and March 31, 1973 in Dunedin’s Queen Mary Maternity Hospital. At regular intervals – 12 times so far – study members are brought back to Dunedin from wherever in the world they live (at the last assessment only a third still lived in the city) to participate in a day of interviews, physical tests, dental examinations, blood tests, computer questionnaires and surveys.
So-called longitudinal studies of this sort seek to provide us with answers to questions on subjects as diverse as child health, injury prevention and links between drug abuse and adult psychosis. They ask how we turned out this way and whether life’s outcomes are the product of nature or nurture. Why, for example, does one person end up heading a successful business while another repeatedly heads to court?
The Dunedin Study, as it is usually called, is one of several cohort projects worldwide. Its findings are broadly the same as those of work that began later in other developed countries, which is why it has long been regarded as one of the very best. However, few outside the worlds of science or social policy know what exactly it is or how it affects us all. A recent documentary series, Why Am I? (now available at TVNZ OnDemand) shines a light on the study and explains why the research is important.
So respected is the study, and such is the worldwide interest in its findings, that it has attracted more than $12.5 million from overseas funding agencies and influenced global thinking and policy-making.
On arrival at her new posting, Moffitt, who is now the study’s associate director, dug into the statistics gathered over the previous 13 years and found teen offending was the norm rather than the exception. More than 90% of adolescent boys and young men had tried shoplifting, cannabis or alcohol. They admitted to fighting in public places, setting fires or other antisocial behaviour, which suggested to scientists – and probably some relieved parents – that such misdeeds are mere rites of passage.
But Moffitt went back through early records of these teens and found that disruptive, bullying behaviour at the age of three was a reliable predictor of criminal offending in later years.
By age 25, most of the criminally inclined study members had grown out of crime. These were dubbed “adolescent-limited”: as they grew up, they began to straighten out.
“They were the ones who were high-spirited, curious and lively with good family support,” Moffitt says. “They were a bit stroppy and didn’t like their parents telling them what to do, but after they have moved on or finished education, they might get a good job, a nice partner and settle down to become an upstanding member of the community.”
This analysis may have underpinned the sentence a Whangarei judge gave to four Northland teenagers for an $80,000 burglary spree: he cited their good family support as a reason for ordering them into community service rather than jail.
A pattern of aggression
A second, smaller cohort of roughly 5% of boys became what scientists termed “life-course persistent”.
“These are the ones who use physical aggression to solve problems all of their lives,” Moffitt says. “Even as young children, they would be hitting people to get what they wanted. They were doing it when we saw them at age 38 and they will still be doing it now.”
This group is also more inclined to end up on a benefit and be addicted to drugs or alcohol.
“They tended to be the same children who were maltreated and neglected. No matter how civilised our society becomes, we will always have a small proportion of people in this antisocial lifestyle.”
Scientists were able to find a gene that was predictive of criminal and violent tendencies, though not everyone with this gene goes on to behave in this way. In the documentary, it is explained in the sentence “it’s as if nature loads the gun and nurture pulls the trigger”. Put another way, nature is the seed and nurture is the sunshine and water.
Girls are much less likely to show criminal tendencies, and the stories of the ones who do are very different from the boys’: the combination of early puberty and older boyfriends is what sends them off the rails.
“They might have a fuller figure but they are still cognitively young,” says Moffitt. “This attracts the attention of older boyfriends, which means access to alcohol and cannabis, being out late at night. They are drawn to this lifestyle through their vulnerability.
“We found the ‘cure’ for it was being at an all-girl school. It means they are somehow protected from boys while they negotiate pubertal change.”
Moffitt accepts that some research suggests all-girl schools may not be as good for learning subjects such as maths, “but when it comes to avoiding getting pregnant or addicted to something, all-girl schools seemed to protect them.”
Long-term studies such as the Dunedin one can translate into changes in policy and practice in the real world, particularly in the justice system. In the past five years, the US Supreme Court has heard arguments based on findings of the Dunedin Study that most youths grow out of crime. It is now case law that a juvenile cannot be sentenced to death, and as a result, 72 adolescents in America have been spared execution.
Among the study’s more surprising findings was that women hit men as much as men hit women. Moffitt says these findings were initially difficult to get published, especially in the 1990s when the women’s shelter movement was strengthening, “but soon the same findings began to appear in overseas studies and people had to accept them as the truth”.
The equivalence can be deceiving, however. Woman are more likely than men to be hospitalised after an incident of domestic violence, and the mental health consequences also differ sharply by gender: women tend to develop depression or alcohol problems.
Moffitt was 29 when she joined the study and is now 60. She works between Duke University in North Carolina and London’s King’s College, returning to Dunedin every couple of years for the assessments.
She says she is “head over heels” for the study, as does its director, Professor Richie Poulton, who calls it the professional love of his life.
Poulton first came into contact with the work as a 22-year-old psychology student.
“I think they chose me because the study members were turning 13 and I had earrings and a ring on every finger while some of the other researchers were grey-haired cardigan-wearers.” He returned more seriously in 1995 and now has grey hair himself.
The scientists in the documentary are happy to be interviewed, but the anonymity of the 1000-odd participants, known as “members”, is fiercely guarded. Poulton calls them “the real heroes”.
In one episode of the documentary, a researcher talks about a man in the study who had been in prison during some assessment phases who said: “I haven’t done much with my life, but I’ve done this.”
“The world owes an enormous debt of gratitude to each and every one of the study members,” Poulton says. “I’m sure they see themselves as just taking part, but they should really hear the message that governments make policy based on how they live their lives.”
A Southland Times editorial called the Dunedin Study the “gift that keeps on giving” and no wonder: it has provided the basis, on average, of a paper for a scientific journal every 13 days for more than 40 years. It has come to be an accurate predictor of everything from criminality to mental-health outcomes, not only for New Zealanders, but other developed countries too.
Looking at yourself
Watching the documentary, you can’t help but reflect on yourself and wonder where you fit in. Among the things you learn are that:
• bed-wetting and thumb-sucking are passing phases with no long-lasting psychological significance;
• self-control is a better predictor of success than intelligence;
• children who watch television for more than two hours a day are more likely to suffer depression; and
• living around pets or other domestic creatures may decrease the incidence of asthma.
Following members from kindergarten to middle age, researchers were able to identify five distinct personality types: well-adjusted, confident, reserved, under-controlled and inhibited.
The first three personality types tend to have better life outcomes and the last two tend to have worse physical and mental health. However, Poulton says nothing is set in stone.
“We talk about trends, not individuals. We don’t see genetic determinism or environmental determinism. Life is a complex interplay between nature and nurture.
“It varies at different points in the life course. There is never a point at which things cannot be changed. The challenge is to make sure that people who need help get it, and get it at the right time for maximum benefit, whether it’s early in life or early in the life of the problem. That’s not cause for despondency; it’s a call to arms.”
Poulton says his work doesn’t push him left or right on the political spectrum. “In fact, I’m the least political I have ever been. I am strongly for the data.”
As a chief science adviser at the Ministry of Social Development, he draws on the study. His most recent high-profile work contributed to the raft of reforms announced by Child, Youth and Family in April, which advocated intensive intervention, support services and a youth justice service aimed at preventing offending and reoffending.
“Using this example, now it’s almost conventional wisdom that you need to get in early, but people forget that wasn’t always known. It was built from studies like ours. Once people start to say, ‘I always knew that’, you know you have succeeded.
“I presume that the Government now and governments to follow will stick with investing in human capital, because it chimes with our life-course results.”
Study members were asked to bring their partners to an assessment when they were in their twenties. The results suggested that we choose people with similar personalities and language-complexity skills. Heavy drinkers had partners who were heavy drinkers.
Additionally, every time a study member has a child who reaches the age of three, researchers pay a home visit and ask a set of parenting-related questions. They record the parent playing a block game with the child and it is later coded at the unit for the type of parenting interaction.
As the study members age, lead researchers scramble to learn new areas. Where once they were experts in early childhood, they later brushed up on aspects of risky sex, juvenile delinquency, alcohol and drug use.
Now they are looking at infertility, job stress, saving for retirement and ageing cognitive abilities.
As researchers move into a new phase, they believe the study will inform the way we spend our retirement and the services we may need to rely on for the future. Funding from the American Institute of Ageing will go towards investigating the increasing burden of an ageing population and looking into early cognitive decline that might be a precursor to Alzheimer’s.
Poulton wants to know the mechanisms of ageing, whether well or poorly. He is personally interested in how social factors contribute to physical decay or damage. “Our mob are only in the infancy of getting older,” he says. “But middle age is when certain problems start to manifest in aches and pains. So we are ideally positioned to see how early life affects later life.”
Next year, as study participants turn 45, they will begin returning to the unit for the next round of testing. To keep the retention rate near 95%, members who are overseas are flown back for assessment. Those in prison or hospital get a site visit.
Members will undergo an eight-hour day of testing, including allergy tests, blood tests and dental examinations. Brain imaging is part of the next phase too. Researchers can see about four people a day, so processing all participants will take 18 months to two years.
Poulton’s hope is that New Zealanders feel proud of the little study that’s doing big things. It is pulling money out of British and American pockets, and although he is only 53 and doesn’t plan to retire until his early sixties, he is already considering the type of person needed to fill his shoes.
“This study is an international treasure and a lot of people are very keen on getting involved. These people range from excellent to nefarious, so although the job is about scientific confidence and skill, you need to remember you are entrusted with a thousand lives – and that really is something.”
Putting it on the telly
Translating what is described as an “avalanche of information” into a documentary for the mass market took almost six years from pitch to broadcast. Study director Professor Richie Poulton received numerous approaches from production houses over the years – including international pitches – but they always failed at the outset because film-makers wanted to speak directly to study members.
However, members are protected by advanced technological firewalls and human firewalls in the form of a handful of trusted individuals.
“By the time Mark [McNeill, the director of Why Am I?] came to me, I was very jaded,” Poulton says. “So I just cut to the chase and said, ‘The bottom line is you cannot go anywhere near our study members under any circumstances.’
“I expected him to harrumph off, but as quick as a flash he said he understood.”
So rather than actual study members, the stories in the documentary are fleshed out through case studies using people who are like the individual or characteristic being described.
The four-part documentary series has an intentionally international feel and has already been picked up by at least 30 networks worldwide.
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