Mothers, don't let your babies grow up to be cowboys
Don't let them ride horses and drive them old trucks
Make them be doctors and lawyers and such . . .

Actually, the intervention needs to start earlier.

Gaps in both cognitive and noncognitive skills between advantaged and disadvantaged children emerge early and can be attributed, in part, to adverse early environments into which an increasing percentage of US children are being born. Figure 1 shows the gap in cognitive test scores by age of children stratified by the mother's education. Similar patterns are found for noncognitive skills (see Heckman, 2008, and Cunha, Heckman, Lochner and Masterov, 2006). Gaps in ability emerge early and persist. Most of the gaps in ability at age 18, which substantially explain gaps in adult outcomes, are present at age five. Schooling plays a minor role in creating or perpetuating gaps, even though American children go to very different schools depending on their family backgrounds. Test scores for children with very different family backgrounds are remarkably parallel with age.

Much of the gap is there by age 3. But is it nature or nurture?

Evidence from the recent literature in psychology and biology suggests that the genes versus environment distinction that was once much in vogue is obsolete. Extensive recent literature suggests that gene-environment interactions are central to explaining children’s intellectual development. For example, breast-fed children attain higher IQ scores than non-breast fed children. This relationship is moderated by a gene that controls fatty acid pathways. Identical twins are affected by life experiences that substantially differentiate the genetic expression of adult twins. Further, the impact on adult antisocial behaviour of growing up in a harsh or abusive environment depends on the absence of a variant of a particular gene. A substantial literature shows that family environments play an independent role in creating adult abilities. Adverse family environments of children create problem adults.

Whatever the genetic endowment, its expression is greatly affected by environment. Genes alone seem not to determine outcomes, but environment does to seem to have a large effect. I suspect that it isn't just mother's milk that is consumed at the breast. There's a large social component to such intimate behaviors.

A divide is opening up in American society. Those children born into disadvantaged environments are receiving relatively less stimulation and resources to promote child development than those born into more advantaged families. Women who are more educated are working and earning more. Their families are more stable and mothers in these families are also devoting more time to child development activities than less educated women. Children in affluent homes are bathed in financial and cognitive resources. Those children born into less advantaged circumstances are much less likely to receive cognitive and socio-emotional stimulation and other family resources. The family environments of single parent homes compared to intact families are much less favourable for investment in children (Moon, 2008).

This makes perfect sense when you consider feedback and multiplier effects.

. . . life-cycle skill formation is dynamic in nature. Skill begets skill; motivation begets motivation. Motivation cross-fosters skill, and skill cross-fosters motivation. If a child is not motivated to learn and engage early on in life, the more likely it is that when the child becomes an adult, he or she will fail in social and economic life.

I find the evidence and reasoning to be compelling. What can be done?

The longer society waits to intervene in the life cycle of a disadvantaged child, the more costly it is to remediate disadvantage.

That's worrisome. What does "intervene in the life cycle of a disadvantaged child" mean? Why is it assumed that the task falls to society rather than parents? There are so many ways that this could get ugly.

One action that seems to be safe and effective is to get the word out. A mother that was not nurtured well herself may not understand that it is important to nurture her own babies. Beyond that, it may be that some mothers would be more nurturing if they could, but they are too busy trying to get by because they are not supported and provisioned by either nuclear or extended families. There's no quick or easy fix for that.