What are the implications of these results? One is that we should not be surprised if even well-designed programs fail over all, because children vary in their susceptibility to environmental influences.

This brings up a challenging ethical question: Should we seek to identify the most susceptible children and disproportionately target them when it comes to investing scarce intervention and service dollars?

I believe the answer is yes. Of course, we have a lot of research to do before that is possible. We need to understand that many genes and even environmental factors are likely to affect how susceptible children are to environmental influences. Thus, we need to move beyond investigations of single genes to examine multiple genes simultaneously, which is becoming possible thanks to advances in DNA sequencing. Some work of this kind already reveals that instead of thinking only in terms of certain children being susceptible and others not, it is more accurate to say that some children are highly susceptible, some are moderately so and some are far less so.

Those who value equity over efficacy will object to the notion of treating children differently because of their genes. But if we get to the point where we can identify those more and less likely to benefit from a costly intervention with reasonable confidence, why shouldn’t we do this? What is ethical, after all, about providing services to individuals for whom we believe they will not prove effective, especially when spending taxpayers’ money?

One might even imagine a day when we could genotype all the children in an elementary school to ensure that those who could most benefit from help got the best teachers. Not only because they would improve the most, but also because they would suffer the most from lower quality instruction. The less susceptible — and more resilient — children are more likely to do O.K. no matter what. After six or seven years, this approach could substantially enhance student achievement and well-being.

Let me say clearly that even if targeting can be done effectively, it doesn’t mean abandoning those who appear less responsive. Every child deserves a decent quality of life, no matter the cost or long-term payoff. Furthermore, money saved by restricting interventions to those most likely to benefit should be used to explore different and conceivably radical intervention alternatives. After all, we don’t know if the children who seem unsusceptible to interventions truly are, or whether they’re simply not affected by what is currently being provided. The ultimate goal should not be to save money, but rather to spend it more wisely.

For now, after half a century of childhood interventions that have generated exaggerated claims of both efficacy and ineffectiveness, we need to acknowledge the reality that some children are more affected by their developmental experiences — from harsh punishment to high-quality day care — than others. This carries implications for scientists evaluating interventions, policy makers funding them and parents rearing children.