Children who are inattentive in kindergarten are more likely to report lower incomes than their peers at the age of 33 to 35 years of age, a study has found.
On the other hand, the most "pro-social" boys -- who help others, are considerate and willing to participate in educational projects -- are overwhelmingly headed for careers that pay more than the average, according to researchers from Universite de Montreal in Canada.
"Over a 25-year career, the differences between the two groups can reach USD 77,000," said Sylvana Cote, lead author of the study published in the Journal of American Medical Association (JAMA) Psychiatry.
"And all this has nothing to do with intelligence or IQ because extreme cases have been excluded from the sampling," she said.
"The differences are significant between the groups studied, but the precise reasons for these disparities are still difficult to identify," said Cote, who specialises in child development.
Problems of inattention more often lead to kids dropping out of school or having trouble adjusting as they enter the labour market.
On the other hand, the researchers found, "prosocial" children are on a trajectory that leads to better-paying jobs.
Researchers used data from over 3,000 kids who were in kindergarten in 1985. Behaviours were evaluated over time through questionnaires.
This is the first time that "pro-sociality" has been studied in a survey of this kind -- and its positive effect came as a surprise to the team.
"We expected to find differences between boys and girls and we did find some important ones," said Cote.
"We expected hyperactivity to be the most important variable, but in fact it turned out to be less important than simple lack of attention," she said.
Differences were evident when data was crunched for in 2015, a year when the grow-ups were in the prime of their working lives and when the wage gaps between individuals were stark.
The researchers said that childhood inattention is associated with a wide range of long-term adverse outcomes, including lower earnings over the course of a career.
They add that early follow-up and care for very inattentive children and boys who rarely express prosocial behaviours "could result in long-term socio-economic benefits for individuals and society."
The researchers also found that women earn only 70 per cent of what men earn.
"This result underlines that the origins of gender disparities in childhood are poorly understood and deserve to be studied," said Cote.