In a long-term study of 43 families, reported in the book Inside the Brain, researchers “found that children who were talked to the most [during their first three years of life] had strikingly higher IQs than children whose parents didn’t talk to them very much.”
... After all, says the aforementioned book, “no one is going to sit next to our children the rest of their lives and help them to study, to do quality work, to think, and to make the extra effort that develops excellent skills.”