Sometimes our folk theories are correct: Parents do shape their children.
According to our folk theories of child development, parents are a major and inescapable influence on their children. Most people believe that how parents treat their children, as well as the values parents impart, leaves a strong and indelible imprint. Yet some psychologists have countered this view and have pointed to the finding that on paper and pencil personality tests, parents and children (especially parents and their adopted children) are often not mirrors of one another. Psychologists have not yet proven to skeptics that parents have a strong influence on their children, but I am convinced that we will be able to demonstrate this.
To begin with, producing children whose personality mirrors ones own is hardly the only way for parents to influence their children. We should not expect children to mirror their parents' personalities since they may often develop personalities in reaction to their parents. If you react against something, that something is having an influence on you. A depressed mother may engender a solicitous child. An impulsive parent may engender a careful child intent on not repeating the parent's errors.
Another problem with only using personality tests to examine parental influence is that these tests ignore political, social, and moral values and aesthetic tastes. I believe that children end up with much of their parents' values and tastes. We know that one of the best predictors of how people vote is how their parents vote. Parental values such as generosity, ambition, materialism, anti-materialism, etc have powerful effects on children. True, children may react against their parents' values. Materialistic parents have bred hippie children. But how many of these children eventually shed their hippie clothing and go to Wall Street? All too many.
If parents had no influence on their children, what is it that keeps psychoanalysts in business? Some children hate their parents. Some feel rage at their parents. Some feel their parents make them feel guilty. Some feel damaged by their parents. Some feel they are carrying on their parents' traditions. Some feel they owe their character strength to their parents. I fervently doubt that these feelings are merely epiphenomenal.
Judith Rich Harris, in The Nurture Assumption, took the position that parents have essentially no influence on their children besides passing on their genes and choosing their children's peer group. Steve Pinker said that the publication of this book was a landmark event in the history of psychology. I disagree with Harris' extreme claims and Pinker's endorsement.
To demonstrate parents' effects on their children, we will need better measures than quantitative short answer paper and pencil personality tests, and we will need to recognize that parents may influence their children to become like them or to become unlike them. One way to start is to develop a set of predictions about how parents shape their children (either to become like or unlike them), interview people about how they believe they have been shaped by their parents, and look for whether the patterns found fit the predictions. A stronger way is to look at adult adopted children, after the tumultuous adolescent years, and look at the extent to which these children either share their adoptive parents' values or have reacted against those values. Either way (sharing or reacting against), there is a powerful parental influence. The way to disprove my claim would be to show no systematic positive or negative relationships between parents and adoptive children. The belief that parents shape their children is part of our folk theory. Sometimes our folk theories are correct.