Why Parents Probably Don't Influence Their Children As Much As They Think

 

Over the years I’ve read a range of work on the nature–nurture question, including research influenced by people like Robert Trivers and by the broader tradition of behavioral genetics. The findings are consistently intriguing - more so than many people expect - especially regarding the surprisingly limited role that parents play in shaping many aspects of their children’s long-term personalities.

Twin and adoption studies give us the clearest evidence. Genetically identical twins share their entire genome whether raised together or apart. Biological siblings share, on average, half their segregating genes. If a trait is strongly genetic, then identical twins- whether reared together or separately - should resemble each other much more closely than non-identical siblings. Conversely, if a trait is shaped mainly by socialisation within the home, then any children raised together, even if unrelated, should become more similar than children raised apart.

Across decades of research, the general picture is clear: a substantial proportion of variability in personality - roughly 40–60% - is attributable to genetic factors, and identical twins raised apart are almost as similar as those raised together. Meanwhile, children who grow up in the same home but are not genetically related tend to be no more similar in personality than two random people from the population.

What’s striking is how small the shared family environment appears to be for personality. Contrary to the earlier assumptions of Freud, Skinner, and other early theorists, the portion of personality differences explained by the home environment shared by siblings is often very modest - near zero for many traits, and only around a few percent in typical contemporary samples. This does not mean parents have “no influence,” but rather that the influence they exert does not systematically make siblings more alike.

Judith Harris made this point vividly, arguing - controversially but with substantial empirical backing - that once a basic threshold of adequate parenting is met, the main environmental shapers of personality are not parents but the broader non-shared environment: peers, friend groups, school cultures, local hierarchies, and the idiosyncratic experiences that differ from child to child. Later researchers have added nuance to this picture, highlighting interactions between genetics and environment, and showing that parental effects often operate in child-specific ways that behavioral-genetics models categorise as “non-shared.”

Still, the overall conclusion remains: parents contribute enormously to children’s well-being, safety, values, and opportunities, but they do not deterministically shape their offspring’s personalities in the way many people intuitively believe. If you took fifty children raised in good, stable environments and hypothetically swapped the parents around, the children would, by and large, grow into much the same adults they were predisposed to become - allowing for the small but real effects parents do have.

This runs counter to common intuition, but the evidence strongly supports it. Children’s genetic endowments and their peer and cultural environments account for much of who they become. Parents certainly matter, but their most reliable influence is in creating conditions that support health, emotional security, and access to positive peer groups and enriching experiences - not in finely sculpting their children’s personalities.

From this perspective, the best a parent can do is not attempt to micro-engineer personality, but rather to provide love, stability, protection, and guidance, while ensuring that a child’s wider environment - schooling, friendships, social groups, and cultural context - is as positive and supportive as possible. Beyond that, much of the trajectory comes from within the child themselves and from the social worlds they grow into.