The events of our childhood can help influence the trajectories of the rest of our lives. The economic status of a family, as well as factors like a child's IQ, have been correlated with various forms of adult welfare, from health to financial stability. But factors like these tend to be difficult to change; why do some people overcome a difficult background, and how might we enable more people to do so? That's the question asked by a research team that has followed over 1,000 children from birth until they were 32, and the results are pretty straightforward: teach the kids a bit of self-control.

The kids in question were born in Dunedin, New Zealand, and enrolled in the Dunedin Multidisciplinary Health and Development Study; 32 years later, a full 96 percent of the initial cohort were still checking in. Along the way, the children, their parents, teachers, and friends reported in on their physical and mental status. Professionals also performed medical and psychiatric evaluations, giving a remarkably complete perspective on the children's development. Hundreds of papers have been produced using the data in the last decade alone.

The latest study focuses on self-control, which seems to be a major interest of the authors. "The need to delay gratification, control impulses, and modulate emotional expression," they note, "is the earliest and most ubiquitous demand that societies place on their children." That sort of self-control remains a major factor throughout adulthood, as we expect individuals to pay their debts, avoid substance abuse, and so forth. And, as the authors also note, there are some indications that self-control can change during an individual's lifetime, and may possibly be learned.

So, they used a battery of tests and surveys—from the children, their parents, their teachers—to generate a composite self-control score for the children at two-year intervals, from ages 3 through 11. They then correlated this score with a variety of measures in adulthood, including general measures of health, substance abuse, financial well-being, and criminal activity. In addition to testing for a direct correlation, they ran a statistical model that controlled for the impact of IQ and the socio-economic status of the child's parents.

Recurrent depression was just about the only thing that didn't correlate with childhood self-control. A health index that covered everything from periodontal disease to STDs showed that low self-control correlated with adult health problems; it also correlated with substance abuse issues. Kids with low self-control were more likely to end up raising kids as single parents, had lower savings, and less put away into retirement or home ownership. Finally, a scan of all the police records in Australia and New Zealand showed that criminal convictions also correlated with low childhood self-control. In some cases, IQ and socio-economic status had more profound effects, but the impact of self-control persisted after these were (ahem) controlled for.

(One amusing aside here is that a lack of childhood self-control didn't seem to make the kids any less likely to still be enrolled in the study at age 32. So, one potential confounding factor didn't seem to play a role in the results, but that seems like a somewhat odd result in itself.)

To strengthen the case for a potential causal relationship, the authors divided up the data in two different ways. They split the total population into fifths based on how much self-control they exhibited as children, and found that the degree of self control also predicted the results of the measures of adult well-being. That is, kids in the middle range of scores tended to have intermediate levels of adult health. They also identified individuals who, over the course of their childhood, had improved their self-control as they transitioned to adulthood. In these cases, the adult outcomes improved as well.

To provide a somewhat stronger control for environmental influences, the researchers also looked at a twin study that had performed a self control test at five, and had data on the individuals when they had reached 12 years old. Already, the kids with less self control were displaying antisocial behaviors, performing poorly at school, and more likely to have started smoking. The authors term these last two "traps," where the lack of self-control early helps lock the kids into habits that will damage their future health and prosperity.

The only obvious weakness of the study is its use of composite scores for some of the correlations. So, although a lot of the health measures are very objective—you don't "sort of" get an STD—the composite health scores lump the STDs in with heart disease and gum disease to create a single value. That runs the risk of accentuating the correlation by pooling a few values that aren't independent. For example, periodontal problems are often associated with heart disease. It also may gloss over some important differences in health risks; STDs, for example, would seem to be a classic self-control issue. But, overall, the work looks pretty solid.

What might set people a bit on edge, however, is the fact that the authors take their work and use it to make policy suggestions. Since it's cheaper to have a healthy, productive member of society, they suggest, governments might consider developing programs that help develop self-control in children as investments in a country's future. In addition, they suggest social programs like retirement savings be made opt-out, since those without self-control would be less likely to bother to skip them, and more likely to need them in their later years. These sorts of policy recommendations aren't typically mixed in with most research papers, which tend to focus on arguing for the direct conclusions from the work.

PNAS, 2011. DOI: 10.1073/pnas.1010076108 (About DOIs).