Researchers can predict which three year olds will grow up to be criminals or beneficiaries with poor health and a high chance of becoming obese.

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The renowned Dunedin Study of 1000 children born between 1972 and '73 looked back at test results for three year olds who had been assessed on their language, motor skills and social behaviour.

The researchers said low scores were a highly accurate indicator for who would end up in what they call "a high cost group".

These are people who make up just 20 percent of the study's subjects but account for 81 percent of criminal convictions and 66 percent of welfare benefits.

The study's director Richard Poulton said the findings shouldn't be used to stigmatise or stereotype but instead tackle childhood disadvantage.

He said neurological assessments of the children when they were three showed those who scored poorly in the tests generally had poorer life outcomes.

"About 20 percent of the population will account for up to 80 percent of the cost to government wherever you look, whether it be in the justice system in terms of convictions, in terms of the Ministry of Social Development in New Zealand concerned about benefit use, the Ministry of Health bed nights used, or pharmaceutical scripts filled," Mr Poulton said.

Gavin Andrews is a professor of psychiatry at the University of New South Wales in Australia and said the first three years of any child's life was crucial.

"At the age of three if you came from a socio-economically deprived family, if you'd been abused, if you were not super bright, and if you had difficulty with self control, your trajectory through life would be much more difficult, in terms of health, wealth and wellbeing."