In a Californian TV commercial, a cheery dad is reading the sports pages from the newspaper with his toddler. "Just a few minutes of reading every day not only builds brain cells, it builds a stronger bond between the two of you," the voice-over intones.

This simple message could change the world. In recent years, neuroscientists have learnt that almost all the brain's development happens by age five. If a child reaches that age well-fed, cared for, read to and talked to, he should end up fine. What happens afterwards - school, university, possibly even prison - probably has less impact on the life course. Now, governments around the world are entering a space they had previously left to the family: early childhood. The public has hardly noticed but wonks can barely contain their excitement.

In an era when most policies are divisive and disappointing, early childhood development has a magic to it. Nurturing kids' brains can improve education, health, childcare, future productivity of the workforce and crime prevention all at once.

Most educated parents are already obsessively nurturing brains. To quote the poet Adrian Mitchell, parodying Philip Larkin: "They tuck you up, your mum and dad/They read you Peter Rabbit, too". By age two, rich toddlers are six months ahead of their poor peers in language proficiency, according to Professor Anne Fernald of the Department of Psychology at Stanford University. That knowledge gap never closes.

If success or failure is already predictable at age two, this undermines the right-wing argument that each person is responsible for his own path. Rewarding winners and punishing losers would make more sense once we have more equal starts.

Indeed, many right-wing as well as left-wing politicians are now embracing early childhood education - the left because it hates inequality, and the right because it hates funding unproductive adults. You know the policy is becoming consensual when a politician as cautious as Mrs Hillary Clinton comes out for it.

Sometimes, early childhood policy can be as cheap as that Californian commercial pushing parental reading. Practically all parents want their children to thrive. Some just don't know how to do it. Perhaps they were never read to themselves, and spent their own childhoods watching TV.

Emeritus Professor of international child health Sally Grantham-McGregor from University College London once told me of visiting a Kenyan village where nobody had books. Some families don't have toys.

But tell a mum why she should talk to her baby during the approximately 3,000 nappy changes in the first year of life, and she probably will. The child will suck in her words. "We are now realising they (babies and toddlers) are the best scientists and the best learners... in the universe," says psychologist Alison Gopnik, of the University of California at Berkeley, in Estela Renner's forthcoming film Be: The Beginning Of Life.

Something else worth telling parents: Don't smack. In a poll by Harris Interactive in 2013, four in five Americans said spanking children was sometimes appropriate. But even light smacks can deform a toddler's brain. What he sees is an angry adult, perhaps twice his size (imagine an aggressor 3.5m tall), about to hit him. He can't be sure it will just be a slap. A child stressed about violence learns to live on high alert. That will damage his concentration, self-control and social skills, and these - more than any intellectual knowledge - predict future success.

Another cheap early childhood policy: Home visits to new mums.

Weekly visits from a social worker to mothers of very malnourished Jamaican children had strong effects 20 years later on the children's IQ, wages, levels of crime, et cetera, Dr Norbert Schady of the Inter-American Development Bank told the ReadyNation conference on early childhood in New York this month.

Pre-school is the more expensive early childhood option, yet it's taking off too. The state traditionally took only kids age four or six, once the damage had already been done, but, now, free schooling from age three is popping up in countries rich and poor. The World Bank backs it. The United Nations' new global "sustainable development goals" include: "By 2030, ensure that all girls and boys have access to quality early childhood development, care and pre-primary education..."

That costs money. However, returns can be immense. The Nobel Prize-winning economist James Heckman, who is the intellectual father of the early childhood movement, estimates that for every dollar put into the famous Perry Preschool in 1960s Michigan, the return to the US economy was between US$7 and US$12.

Spending on older people was much less efficient, he calculated. Even by age 18, minds have mostly formed. Forty-five per cent of US students "did not demonstrate any significant improvement in learning" during their first two years in college, estimate Richard Arum and Josipa Roksa in their book, Academically Adrift. And that's at great expense.

A professor at a well-reputed US state university once told me his students' parents spend about US$200,000 on tuition and living expenses during the four-year degree. Many of those students, he said, spend those years drinking beer. Better to invest in babies instead.

THE FINANCIAL TIMES