Working with children at more than 200 preschools in India, researchers found that those who took part in math games for four months became more skilled at math assessments similar to those they'd see in primary school - an effect that lasted for up to a year. The study represents one of the first efforts to field-test a critical assumption in modern psychology; namely, that children's learning of the symbolic mathematics taught in primary school would be facilitated by activities that exercise their intuitive cognitive abilities during preschool years. Children in developing countries are often under-prepared for demanding primary school curricula, particularly in math, with poor curricula being thought partially to blame. Decades of laboratory research into development of children's mathematical reasoning have attempted to show what needs to be learned before a child is ready to begin math, suggesting that preschool-level training with numerate adults who engage children's basic numerical abilities could help. Here, to understand whether such efforts could be effective outside the lab, Moira Dillon and colleagues conducted a study involving more than 1,500 children in 214 resource-poor preschools in Delhi, India. Some received math training from adults, while others received social training, or no training at all. Children who played the math games improved in areas like knowledge of number words and symbols, the researchers report, while their peers (with social or no training) did not noticeably improve. The gains in the first group persisted up to a year, the researchers say, though they did not trickle over into the comprehension of math concepts during primary school. Even so, the findings may inform efforts to reform school curricula using basic science.