According to the Brookings Institution, preschool is already too late for low-income kids who may be understimulated. Some problems begin even before birth: “… in animal studies, stress during pregnancy impedes neural development in the fetus and has a major impact on structures underlying self-control, attention, and memory. Beyond stress, toxins, nutrition, and physical health, other aspects of maternal health also affect brain development.”
But enriched environments make a huge difference: “Even more encouraging, brain imaging of children who are removed from adverse situations—such as those reared in institutions in Romania—demonstrates that when children are put in an enriched environment, they catch up in some aspects of brain development, while their peers who stay behind do not. This change is also reflected in their brain functioning. As in many animal studies, these results demonstrate the impact of enriched environments and improved caregiving on brain growth.”