It's really hard to know exactly what things effect a Childs Development and to know exactly how and why these effects happen. And more importantly, how would you tell when certain thought processes have been adversely effected and what steps would you have to take to correct these particular thought processes or behaviors? What are these key moments in a Childs life that can have a profound effect on their thought processes? First you would have to be totally aware of everything in the Childs life that they are exposed to. Like everything they see, touch, hear, taste and smell in their environment, the people they are in contact with, the amount and type of TV and other media they are exposed to, what type of music they listened to, everything they ate and so on and so on. Then you would have to Follow a Child Around all day and correctly examine how they interact with the environment and other people. And then when they're old enough to be able to speak in sentences you would have to follow a child around all day and constantly ask them "So what are you thinking now?" But even then how would you be sure that a child could actually understand the question in order to answer it accurately. I know we have the abilities to understand how important child development is, but the question is, when will we start teaching it to everyone?
Alison Gopnik: What do babies think? (Youtube)   
What Is It Like to Be a Baby: The Development of Thought (Youtube)  Yale Course (PSYC 110)