Common Sense and Bias

According to Judith Rich Harris, researchers tend to seek out evidence that confirms their biases, and downplay (or attack) any evidence to the contrary.  Furthermore, according to Christopher Chabris "people often react most defensively when challenged not on their firmly held beliefs but on beliefs they wish were true but suspect at some level to be false." 

For example, psychologists often assert that a child’s personality can be guided and shaped by his or her parents.  This implies that well-adjusted children must have had good parents, and fearful children must have been overprotected by their (bad) parents.

This common sense view completely overlooks the possibility that children who are born with a genetic predisposition to be anxious or fearful are more likely to be reared by anxious, fearful parents, because children get their gene variants from their parents as well as their environment.

When asked to consider this, researchers have backtracked, and now claim it’s not parental over-protectiveness that makes all children fearful, it’s the child’s "high-reactive" temperament.  So overprotecting some children makes them fearful, and overprotecting other children does not... Which begs the question -- how can you predict who react which way?

Another example of bad research shows that “mothers who improved in their child-rearing methods (through interventions) are more likely to have children who behave well in school”.  Due to their biases, researchers overlooked the fact that “compliance depends on certain personality traits that may also be associated with the outcome event”. 

In other words, “people who comply with interventions are likely to differ in personality and intelligence from those who do not comply. Because these characteristics are heritable [innate], parents who respond well to the demands of an intervention are more likely to have children who respond well to the demands of school.”  Again, children share their parents' gene variants, not just their environment.