At first impression, the two groups of children were hard to tell apart: just regular kindergarten kids from different neighbourhoods in Kamloops, B.C. Yet, when they visited a mobile lab as part of population study he collaborated on, Clyde Hertzman remembers how their young brains revealed a striking contrast.
Both groups were asked to focus their attention on a series of sounds while researchers monitored their neural activity. Not only did one group tend to have a harder time with the task, Dr. Hertzman recalls, it “ had a systematically different pattern of brain responses to the test.”
How could children drawn from a city of just 85,000 people end up with wiring that was essentially different? They had grown up with any number of genetic and environmental influences affecting their brain development and behaviour, but one variable stood out: affluence. Those who did not perform as well tended to be from the poorer of the two neighbourhoods. Somehow their socio-economic status was showing up in the architecture of their thoughts.
The result was a particularly vivid example of something scientists who specialize in early childhood development have seen again and again. Kids from communities that are underresourced and subject to economic stress think differently than their wealthier counterparts in ways that can ultimately affect behaviour.
Five years later, Dr. Hertzman – who teaches at the University of British Columbia’s School of Population and Public Health and was Canada’s health researcher of the year in 2010 – is part of a rapid evolution of the field that has grown from merely recording the demographics of cognitive disparities to building a bottom-up understanding of the molecular changes that cause them.
The change has gathered momentum in recent months, fuelled by a bounty of new findings that bolster the long-observed link between social environment and development with a newly emerging biological perspective.
It also underscores the stunning human cost of what is called the “socio-economic gradient.” Only 3 to 4 per cent of Canadian children are born with inherited differences that will limit their physical, emotional or intellectual growth, yet an average of 25 to 30 per cent exhibit some level of developmental vulnerability that could include a cognitive “deficit.”
In some communities, the figure may reach 70 per cent, and by adolescence, the resulting deficits can translate into a range of mental-health issues, substance abuse and diminished opportunities for education and employment.
The Royal Society of Canada and the Canadian Academy of Health Sciences issued a report in November that surveys the new research on how socio-economic factors can affect someone’s biological makeup – and warning of “dire consequences for the individual and society” if nothing is done. The report concludes by calling for a broad strategy of investment in early childhood.
“If a society wants to ensure the best trajectory for its children, its policy focus should be on those early years,” says Alan Bernstein, president of the Canadian Institute for Advanced Research (CIFAR), which supports several leading scientists in the field.
A key feature of the emerging connection between brain and poverty is stress. While economic status does not necessarily spell bad news for a given child’s development, it tends to dovetail with parental stress and family stability in a way that can strongly shape how a young brain experiences the world.
At the extreme end, low socio-economic status and the stress that underlies it can mean higher incidences of physical and emotional abuse. But it can also lead to a broader, more subtle type of social adversity – parents or caregivers have less time, or are less inclined, to nurture their children.
The potential risk is illuminated by a proliferation of genetic studies that, by comparing the DNA, uncover hidden variants that could affect how children develop in response to adversity.
But genes are hardly the development dictators they are sometimes made out to be. Instead, the quality of the nurturing environment, often through the presence or absence of stress, can determine whether a genetic difference actually matters.
“The genes, in a sense, are listening to the environment,” says Marla Sokolowski, who specializes in genetics and behavioural neurology at the University of Toronto.