Half of adult personality is determined by heredity. The other half of adult personality is determined by the child's peer group. The percent of adult personality determined by parenting is zero, zilch, none, nada. Half of adult personality is determined by heredity. Here Harris is on firm scientific grounds.
Cute babies receive more attention and affection than babies who are cuteness-challenged.
The percent of adult personality determined by parenting is zero. Harris is so insistent about this point that one gets the impression she would have made the percent even lower if that were mathematically possible. Harris correctly rejects most of the personality development research because it confounds heredity with parenting. If parents who behave a certain way have children who behave a certain way, this does not mean that the parental behavior was the cause of the child's behavior. For example, if strict parents have rebellious children, this does not mean that parental strictness caused the children to rebel.