How can we disentangle nature and nurture? (S1EP17)
Summary
TLDRIn this insightful discussion, the speaker explores the role of genetics in shaping human behavior, drawing on the 'three laws of behavioral genetics'. The first law asserts that all behavioral traits are partly heritable, with genetic differences contributing to individual variations. The second law reveals that genetic effects often surpass familial ones, challenging the notion that family environment is the primary influence on development. The third law introduces the concept of non-shared environment, emphasizing the significant role of chance and unpredictable factors in personal development. This talk sheds light on the complex interplay between nature and nurture in defining who we are.
Takeaways
- 🧬 All behavioral traits are partly heritable, meaning genetic differences contribute to the variations among individuals within a culture.
- 👥 Identical twins, even when raised apart, show remarkable similarities, suggesting a strong genetic influence on behavior and personality.
- 🏠 The impact of family environment on personality and intelligence is often surprisingly small or even zero, especially when comparing identical twins raised in different families.
- 🌱 The effects of genes are generally stronger than those of family environments, challenging the common belief that parenting styles heavily shape children's outcomes.
- 🧐 There is a significant amount of variation in human behavior that is neither genetic nor familial, indicating other factors beyond genes and family influence.
- 🤔 The concept of 'chance' plays a significant role in personal development, encompassing unpredictable and immeasurable factors that contribute to individual differences.
- 🧪 Advances in DNA analysis allow for the observation of statistical correlations between genetic variants and behavioral traits, reinforcing the idea of genetic influence.
- 👭 Comparisons between identical and fraternal twins provide a powerful method for understanding the role of genetics in behavior.
- 🌟 Judith Harris, a psychologist, highlighted the importance of considering genetic overlap to avoid misattributing parenting effects as heritability.
- 🌐 Cultural differences do matter, as seen in comparisons between vastly different societies, but within the same culture, genetic differences play a more significant role than cultural upbringing.
Q & A
What is the main argument presented in the script about human traits?
-The script argues that human traits are a result of evolution and are partly heritable, meaning that genetic differences contribute to the variations we see among individuals.
How does the script suggest that our genetic makeup interacts with our experiences?
-The script suggests that our genetic makeup interacts with our experiences to shape who we are, but it also emphasizes that the genetic effects are often stronger than the effects of our family environment.
What are the 'three laws of behavioral genetics' mentioned in the script?
-The three laws mentioned are: 1) All behavioral traits are partly heritable. 2) The effects of genes are stronger than the effects of families. 3) There is a lot of variation that is neither genetic nor familial, suggesting a significant role of chance in development.
How does the script explain the heritability of behavioral traits?
-The script explains heritability by discussing studies comparing identical twins who share all their genes with fraternal twins who share half their genes, as well as studies on identical twins separated at birth and raised in different environments.
What role does the script suggest that family environment plays in shaping our personalities and behaviors?
-The script suggests that the effects of family environment are often surprisingly small or even zero, especially by the time individuals reach adulthood, compared to the impact of genetic factors.
Why does the script find the impact of family environment on development surprising?
-The script finds it surprising because people often attribute differences in children's outcomes to parenting styles and family dynamics, but research in behavioral genetics indicates that these factors have less impact than previously thought.
What is Judith Harris's contribution to the understanding of behavioral genetics discussed in the script?
-Judith Harris is credited with highlighting the robust findings from behavioral genetics that were often ignored, particularly the idea that genes matter more than family environment in shaping an individual's development.
How does the script address the misconception that environment and heredity are inversely related?
-The script clarifies that environment and heredity are not inversely related in the way people often assume. It argues that there is a significant amount of variation that is neither genetic nor familial, indicating that other factors beyond genes and family environment play a role.
What does the script suggest about the role of chance in our development?
-The script suggests that chance plays a significant role in our development, including random events such as mutations, brain development variations, and unpredictable life experiences that contribute to making us who we are.
Why does the script consider the findings from behavioral genetics to be counter-intuitive?
-The script considers the findings counter-intuitive because they challenge common beliefs about the importance of family environment and parenting in shaping individuals, instead highlighting the strong influence of genetics and the role of chance.
Outlines
🧬 Genetics and Behavioral Traits
The paragraph discusses the impact of genetics on human behavior and traits. It highlights that talents and temperaments are a result of evolution and are coded in our DNA. The author introduces the concept of behavioral genetics and the 'three laws' that govern it. The first law states that all behavioral traits are partly heritable, meaning genetic differences contribute to the variation among individuals within a culture. The author explains this through the comparison of identical and fraternal twins, as well as identical twins separated at birth and raised in different environments, showing that genetics play a significant role in shaping who we are.
👨👩👧👦 The Surprising Minimal Impact of Family
This paragraph explores the second law of behavioral genetics, which suggests that the effects of genes are stronger than those of family environments. The author challenges the common belief that family upbringing has a lasting impact on a person's intellect and personality. By examining the cases of identical twins raised in different families and adoptive children, the author illustrates that shared genes have a more significant influence than shared family experiences. The author also critiques the assumption that parenting practices directly shape children's outcomes, arguing that genetic predispositions might be mistakenly attributed to environmental factors.
🌟 The Role of Chance in Personal Development
The final paragraph delves into the third law of behavioral genetics, which posits that a significant amount of variation in behavior and traits is neither genetic nor familial. The author discusses the difficulty in quantifying the impact of 'chance' on personal development, which includes unpredictable events and factors beyond genetics and family environment. Examples include mutations, random developmental events, and unique life experiences. The author emphasizes the importance of acknowledging the role of chance in shaping individual differences, suggesting that it is a critical factor in understanding human diversity.
Mindmap
Keywords
💡Evolution
💡Genome
💡DNA
💡Heritability
💡Identical Twins
💡Fraternal Twins
💡Behavioral Genetics
💡Environment
💡Judith Harris
💡Chance
💡The Blank Slate
Highlights
Talents and temperaments are a result of evolution, influencing brain development and genetic makeup.
Genetic endowment interacts with experience to shape individual differences.
The majority of human genes are shared, contributing to our unity as a species.
Differences among individuals are partly due to genetic variations.
Modern DNA analysis reveals correlations between genetic variants and behavioral traits.
Behavioral genetics findings are replicable and almost law-like.
First law: All behavioral traits are partly heritable.
Second law: Genetic effects are stronger than family environmental effects.
Third law: There's significant variation that is neither genetic nor familial.
Identical twins studies show genetic overlap's role in personality and behavior.
Separated identical twins raised in different families remain remarkably similar.
Family environment has surprisingly little lasting impact on adult personality and intellect.
Cultural differences are significant, but within-culture family effects are minimal.
Parenting effects may be confounded by genetic inheritance.
Judith Harris' insights challenge traditional views on the impact of family and environment.
Chance events, such as mutations and random developmental factors, contribute to individual differences.
The role of chance in development is significant and often unpredictable.
Behavioral genetics findings are counter-intuitive but robust.
The 'three laws' of behavioral genetics offer a new perspective on human development.
Transcripts
foreign
[Music]
with certain talents and temperaments
that they're a result of evolution just
like our our bodies then there's got to
be a way in which they play themselves
out in the development of the brain and
of course that information is coded in
our on our genome in our DNA
a key question is how does our genetic
make up our endowment interact with our
experience to make us who we are in
particular to make us what makes us
different from one another
there are things in our genome that we
all share the vast majority of our genes
are the same as every other human and
that's what's responsible for our Unity
as a species but of course we're not
clones people are different and one can
ask how do we get different
the chapter on children on the
development of children in my book the
blank slate was probably the most
controversial of the 23 chapters even
though there were plenty of hot buttons
in that book such as politics and
violence and sex differences and
discussions of rape and murder and War
and liberal versus conservative
ideologies there's a chapter of children
that that really got people uh hot and
bothered and it came from reporting what
I've come to be known somewhat
informally as the three laws of
behavioral genetics now psychology
doesn't have laws the way physics has
laws but there are findings that are so
replicable over so many studies of
hundreds of thousands of people that
they almost deserve to be called laws
the first law is that all behavioral
traits are partly heritable
what does that mean it means that some
of the variation within a culture
between one person and another what
makes Jason different from Sam what
makes Emily different from Jessica comes
from differences in their genes
how do we know that well nowadays we can
have people drool into tubes and look at
their DNA and we find that there are
massive statistical correlations between
our thousands of genetic variants and
any trait that we try to measure but way
before there were there was that
technology still really in its infancy
there were powerful but simpler methods
of establishing the effect of genes for
example you could compare identical
twins who share all of their genes and
their environment with fraternal twins
who share half their genes and their
environment if the identical twins are
more similar to each other than the
fraternal twins it suggests that their
greater amount of genetic overlap has a
role and there are many complications
and asterisks and digressions that have
been worked out over the decades but the
finding is pretty solid or for that
matter you could look at the special
case of identical twins who are
separated in birth and raised in
different families sometimes different
continents and finding is that they are
remarkably similar not indistinguishable
but but more similar than uh to people
who even grew up in the same family
so the first law is that all traits are
partly not completely but partly
heritable
second law of behavioral genetics turns
up in study after study whatever you
choose to measure whether it's
personality character intelligence
habits smoking drug addiction a number
of books that you read number amount of
Television that you watch likelihood of
getting into trouble with the law that
the effects of the genes are stronger
than effects of families and in fact
often the effects of families are
surprisingly small indeed Zero by the
time you're an adult now this people
find mind-boggling but here's the
rationale behind it remember those
identical twins that were separated at
Birth and brought up in separate
families and you know they're pretty
similar because they have the same genes
even though they were brought up in
different families okay well now compare
them to identical twins that were
brought up in the same family now you
might think wow well they should be
really similar because not only do they
share the
but they also share the same parents the
same neighborhood the same older
siblings the same younger siblings so
they should be much more similar and the
answer is they're not in fact in general
adopted kids who grow up in the same
home are no more similar by the time
they're adults that adopted kids who are
who grow up in separate homes all those
years of growing up with with those
parents leave surprisingly little
lasting stamp on your intellect and
personality now by the way this is not
to say that your culture doesn't matter
culture does matter as we see in
comparing say you know manhattanites
with indigenous people in the Amazon
rainforest or Papua New Guinea or
Bedouins culture obviously matters a lot
but if you were to switch the kids
around in different families within the
same culture you find that there's
surprisingly little effect
hate to interrupt wouldn't you prefer
uninterrupted Indulgence head to find
qualia.com to access the entire series
by The Genius Stephen Pinker completely
ad-free
now people find this mind-boggling
because they look at parents and they
look at kids they see the obvious uh
connection between how the parent
treated the kid and how the kid turned
out and they say well parenting
obviously shaped them but the problem is
that unless you're looking at adoptive
children and their parents you have a
massive confound namely the parents give
their children an environment parents
also give children their genes unless
you have adopted families you can't
tease them apart and when you do tease
them apart with adoptive households you
see that genes matter much more than
families so the fact that parents who
talk more to their kids have kids who
end up with better language skills the
fact that people who spank their kids
end up with kids who are more violent
doesn't necessarily mean that talking to
your kids makes them better at language
it might just mean that people who talk
more have genes that make them more
linguistic and they pass those kids
those genes on to their kids people who
are violent to their kids are more
temperamentally violent that can
inherent that temperament they're more
violent too this is a massive problem in
a lot of social science research where
if you don't take into account the
genetic overlap you can misattribute
effects of heritability and falsely
think that their effects of parenting
this by the way is an Insight that comes
from a psychologist named Judith Harris
she never had a university job because
she was kicked out of graduate school
for not fitting The Stereotype of a
psychologist she ended up turning the
field on its ear by calling attention to
these very robust findings from
behavioral genetics that people tended
to ignore
now the first law is that all behavioral
traits are heritable second law is that
effects of genes are stronger than
effects of families which are often weak
to zero the third law is there's a lot
of variation that is neither genetic nor
familial now people have a lot of
trouble wrapping their heads around this
because everyone thinks oh well there's
heredity there's environment the more
heredity the less environment and vice
versa but actually that turns out not
not to really be true at least if you
consider the environment to be something
that you could really look at or measure
like the effects of families here's the
findings really not all that complicated
let's go back to our identical twins who
are reared together in the same
household
okay they got the same DNA genes are the
same same mother same father same older
siblings and younger siblings same
number of books in the house same number
of TDS in the house same teachers same
same everything so they should be
absolutely indistinguishable they should
be you know clones well if you know a
pair of identical twins you know they're
not indistinguishable they have separate
personalities I know this intimately
having two identical twin uncles Barry
and Mark who are more similar Than
People picked off the street at random
but no one in the family had any doubt
which was which they each had their
personality and that's true of all
individuals
that leads to a real puzzle that I think
psychologists have not really
thought through enough which is
how can they be different
it's not their genes it's not their
environment at least not anything stable
about the environment like who your
mother is or what what neighborhood you
live in
suggests to me that there is a massive
effect of chance on the development of
Who We Are
what do I mean by chance well chance all
kind of Embraces everything that uh that
we can't predict and measure it could be
chance events in the genome new
mutations happen with every baby and
when you have even identical twins who
come from an egg splitting into two
there could be a mutation that develops
in one fertilized egg and embryo but not
in the other there are mutations that
develop as in our bodies as we grow and
develop that could be different in the
two twins there could be factors in
brain development that the genes can't
control down to the last synapse it
could be that growing axons in the brain
of one twin Zig on in one day and they
zag and the other that could be random
factors in development that you don't
take into account when you just look at
families like you know who got the top
of the bed who got the bottom bunk bed
did one child get chased by a dog one
day and the other one not or get teased
by his friends or picked on by a bully
all of these things seem to add up to
make us who we are in a way that we
could never really pin down in our own
autobiographies that we could never pin
down in most scientific studies but may
have a huge effect in uh in who we are
these are the three counter-intuitive
findings from behavioral genetics again
massively replicable that I tried to
explain in the children's chapter of the
blank slate with full credit to Judith
Rich Harris that I consider to be among
the most interesting things I've
discovered about the mystery of Who We
Are
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