The Nurture Assumption: Why Children Turn Out the Way They Do

A groundbreaking title claims parents have little impact on their child’s development.

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Karsen: From The Parent’s Club, I’m Karsen Kolnicki. This is your briefing.


Karsen: Today, we’re discussing The Nurture Assumption: Why Children Turn Out the Way They Do. Written by Judith Rich Harris.

In this title, the author combines insights from psychology, sociology, anthropology, and evolutionary biology to explain how and why it’s good that children typically take cues from their peers.

Karsen: Vincent Phamvan on the key takeaways [pause] and what you need to know.


Karsen: Vincent, this author takes the radical view that parents don’t have as big of an impact on their children’s personality as they may think. Why does the author argue parents have little impact on their children’s development?

Vincent: As a former college textbook author, Judith Rich Harris took a pretty radical view when this book was originally published in 1998. Ten years later, she released an updated version to provide a fresh view of the latest research.

For decades, people have believed that parents play a major role in how their children turn out. The common thought is that a child’s personality is formed by nature (such as their genes) and nurture (or the environment in which they are raised).

However, the author looked at the research from development psychologists and believes that the nurture assumption is a cultural myth. The reason, she says, is because parents are not the only influential factor in a child’s life. Everyone from their friends, peers, teachers, and even basketball coach can have a lasting impact on their personality.

Karsen: I grew up with a house of siblings, but I’ve definitely felt that in some ways, I’m very different from my siblings.

Vincent: The research shows that your genes definitely can have an impact on your personality. When you look at genetically identical twins, there have been several studies that found that even when they grow up in different environments, they end up with very similar traits.

There’s a famous Minnesota Twin Family Study from 1979 to 1999. One of the pairs of twins were two brothers named Jim. They grew up in very different environments, but when they met later in life, they found that they both bit their nails, were interested in woodwork, and drove the same car.

Karsen: Wow, that’s fascinating.

Vincent: Yea, and on top of that, they even liked the same brands of beer and cigarettes.

Karsen: So what happens when the twins grow up in the same home?

Vincent: The author argues that even when they grow up in the same home, they don’t have any more similarities. She says that’s because the similarities are driven by genetic makeup.

The same study looked at personalities of twins who were raised in the same house. It looked at how shy the children were as well as whether they were agreeable or not. They found that the traits correlated by just 50 percent. That means they were no more similar than when the twins grew up in different environments.

Karsen: So that means parents may not have as much control as they think over how their children will turn out. But isn’t a child’s character influenced by their parent’s behavior?

Vincent: Harris argues that although a child’s behavior is influenced by their parents, it’s just as equally influenced by others outside of the family. So how a child behaviors around their mother will differ from when they’re with their classmates.

Karsen: So children will adapt their behaviors based on who they interact with.

Vincent: Yea, that makes sense, doesn’t it?

Karsen: It does. So it doesn’t mean that parents don’t have any impact. It just means that there are more factors outside of just the parents.

Vincent: Right, so if a child’s mother is depressed and barely ever smiles around the child, the child may look more sad when they’re together. However, the same child could be very warm, and happy when they’re at daycare with an upbeat teacher.

Even if the child mimics their mother, the sadness is not a lasting part of their personality.

Karsen: So do children primarily learn through mimicking behavior?

Vincent: Most children developmental experts say yes. Many wonder if a child living in isolation would automatically acquire language skills, but obviously running that experiment would be impossible… and unethical.

However, in the early 1930s, a psychologist took an infant chimpanzee and raised it in his own home alongside his infant son, Donald. The human child would often imitate the chimpanzee.

Karsen: That’s pretty crazy.

Vincent: It’d be an interesting environment for sure. But anyway, eventually Donald would start expressing himself like the chimpanzee by barking when he was hungry. Donald also fell behind in learning English.

Usually by 19 months, children know about 50 words, but Donald only used three. So it looks like the experiment inhibited Donald’s early language development, so the study ended here.

Although it had an impact on Donald, it also showed that Donald didn’t need his parent’s help to learn a language.

English wasn’t the primary language in my household growing up, even though it was the local language spoken outside my home. So children will pick up the language even if they have hearing impaired parents or immigrant parents. They’ll still learn the language from their peers or from someone else.

Karsen: If the parent’s role is not as essential as you would think, why do children often cry when being dropped off at school or when a babysitter shows up at the house?

Vincent: Well, young children definitely like having their caregivers close by. The mother-child relationship is very strong. Mothers provide security, nutrition, and comfort. They can intervene if a playmate gets too aggressive. This is built into a child’s survival mechanism.

There was one study where researchers put two babies in a room with their mothers. Even when the children were busy playing, they still watched their mothers to make sure they stuck around.

However, even despite this, Harris argues that peers can be a substitute for a child’s mother. Some of this thought was influenced by a study by psychoanalyst Anna Freud which observed six children rescued from a Nazi concentration camp. They were around three or four years old.

Karsen: That’s so sad. What happened to their parents?

Vincent: Well, all of them lost their parents and close caregivers in the concentration camp. However, the children stuck together and were really attached to each other. When the group was separated, they grew upset. On top of that, when they played with each other, they showed no signs of rivalry. They even handed food to each other, which is not a common trait for children this age.

Karsen: So the children were replacing the roles that their mothers would play?

Vincent: Even though they had a really traumatic past, they still found ways to grow up healthy. All of them grew up to become well-adjusted adults.

Harris goes a step further in showing how peer influence explains why boys and girls behave differently and play with different toys.

Karsen: So she says that this doesn’t have to do with how their parents treat them?

Vincent: Even though boys and girls have many similarities, Harris says that children typically don’t become more masculine or feminine because of parental expectations. She says this occurs because of interactions with peers.

So once they categorize themselves as a boy or girl, the children will observe how other children of their gender act, and they will behave accordingly.

Karsen: So the author believes that children socialize like the other kids of the same gender. That makes me think about how teenagers want to be more like their peers, and to some extent even avoid acting like adults.

Vincent: Exactly. As children grow into adolescent years, the influence of peers becomes more prominent. It’s not because parents don’t have an impact, but rather that they want to maintain status in a group of peers.

Children will imitate their “superior” peers.

Karsen: Ahh, the cool kids.

Vincent: Yes, the popular kids. The goal for many teens is to avoid humiliation within the group. There was a 1987 study that found that kids believe being shunned by their peers in school was the third-worst thing that could happen to them.

Karsen: What was number one and two?

Vincent: Losing a parent and going blind.

Karsen: Wow.

Vincent: So this study showed that the sense of belonging to a group is what makes teenagers so rebellious. Teenagers see themselves as part of their group, which has different rules than what adults believe the rules should be.

Karsen: Which would explain why teens are not happy when adults tell them how to dress or how to behave. They’re focused on protecting their status within the group.

Vincent: Yes, they want to fit in with their peer group, which oftentimes is at odds with how adults behave. It’s more important to signal that they are not in the adult group. During these years, they’re in an inbetween, where they’re not necessarily children, nor are they adults.

Karsen: So the peers that your kid surrounds themselves with matter a lot.

Vincent: Definitely. You’ve likely heard the phrase that you’re the average of the five people you spend the most time with. This is one of the biggest effects on a child. Peer pressure will affect your teen a lot more than the advice that you give them. So if you want to make sure your child succeeds academically, then they need to have good friends.

Enrolling them in a school with peers who are geared towards good grades and care about their academic achievements will make it easier for your child to do the same and be excited about it.

Karsen: It sounds like the key takeaway from this book is that parents are not solely responsible for their children’s character. They are one of many factors that influences how a child behaves. Children can also be influenced by peers, siblings, culture, and their genes.


Karsen: That’s it for your briefing. I’m Karsen Kolnicki.

Vincent: And I’m Vincent Phamvan.

Karsen: We’ll see you next time.


This groundbreaking book, a Pulitzer Prize finalist and New York Times notable pick, rattled the psychological establishment when it was first published in 1998 by claiming that parents have little impact on their children’s development. In this tenth-anniversary edition of The Nurture Assumption, Judith Harris has updated material throughout and provided a fresh introduction.

Combining insights from psychology, sociology, anthropology, primatology, and evolutionary biology, she explains how and why the tendency of children to take cues from their peers works to their evolutionary advantage. This electrifying book explodes many of our unquestioned beliefs about children and parents and gives us a radically new view of childhood.

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