What is interesting about this study is the added benefits discovered; improvement in learning, and less involvement in violent activity.

Toddlers in a program to encourage interaction and play with their mothers grew into adults with higher IQs, greater educational attainment and less involvement in violence than kids who did not receive the early stimulation, a new study finds.

These latest results are the fourth follow-up in a series of studies since the early-childhood program ended, about 20 years ago.

"The most exciting finding this time was the reduction in violent behavior, because that's something we haven't shown before," said Dr. Susan Walker, the lead researcher and a professor at the University of the West Indies in Jamaica.

Beginning in the 1980s, Walker and her colleagues tracked 129 Jamaican toddlers who all had stunted growth and lived in an impoverished area.

One group of children was part of the stimulation program, another was given supplemental baby formula, a third group received both interventions, and a fourth group did not get either.

The stimulation involved a weekly visit from a woman who taught the mothers how to play with their toddlers and engage them in everyday activities, and who also left toys and books each week.

Children who received food every week were given 1 kg of milk-based formula, which makes a little less than two gallons.

Each intervention lasted two years.

As in previous follow-ups, Walker found that children who received the stimulation from their mother had higher IQs. In this study of the participants at age 22, there was a six-point difference between those who had received the interaction and those who did not.

"It's a substantial improvement for something that took place in early childhood," Walker told Reuters Health.

Children who were stimulated were also 65 percent less likely to be involved in fights and violent crime as adults, and they performed better in math and reading tests.

The group of toddlers who received formula had no improvements in these measurements two decades later, compared to kids who did not get the extra food.

None of the interventions were tied to any differences in alcohol or cigarette use, teenage births, or education past secondary school. And the participants remained small compared to their peers - likely the result of poor nutrition as babies, Walker said.

Dr. Benard Dreyer, a pediatrics professor at New York University School of Medicine, who was not involved in the study, said the results show that the benefits of early childhood stimulation can ripple for years - increasing the likelihood of excelling in school and avoiding violence.

In an editorial he wrote in the journal Pediatrics, where the study is published, Dreyer said such programs should be offered to poor children in the United States and the developing world.

"It's not that we don't know what to do, it's that we haven't decided to implement this on a large scale," he told Reuters Health.

No one knows what a program like this would cost, but it’s estimated that in-home interventions would be less expensive in the long run  by helping to reduce high drop out rates and incarcerations.

Dreyer added that Walker's study is one of the few well-planned interventions followed-up for so many years.

Walker suggests that early-childhood intervention for children who are deprived of nutrition and stimulation should become part of regular pediatric services, just like immunizations.

"In this context, where there are virtually no toys in the home and maybe not much language interaction, what you do to improve the quality of that mother-child interaction and the engagement in play can be tremendously important," Walker said.