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Chapter 3 GP 4,5 & 6

Psych 30

NWRC

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4 How do scientists study therelative influences of

heredity and environment

and how do heredity andenvironment work

together?

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Heritability

Heritability is a

statistical estimate

of how great

contributionheredity makes to

individual

differences in a

specific trait withina given population

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Family Studies

In family studies it is

quite difficult for

researchers to

determine whethercertain traits are

caused by heredity

or environment.

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Family Studies

A good example

would be obesity

are the children

overweight becauseof heredity, or

because the whole

family overeats

together(environmental)?

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Adoption Studies

This is why

researchers like to

do adoption studies

where the effects ofheredity can be

separated from the

effects of

environment.

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Adoption Studies

Studies of monozygotic

twins separated at birth

are particularly

interesting toresearchers as they

have shown a

hereditary basis for

many concordant traits

that are not explainedby environment.

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Adoption Studies

Adriana Scott was adopted fromMexico when she was just weeks old.While growing up on Long Island, N.Y.,she noticed that she looked nothinglike her cousins.

She had no idea why she excelled at

certain things. Im very into music andinto dancing, she says. My familysnot like that, really.

And she always believed her quirkswere hers alone: Nothing like, Oh, Igot this from my mom, or I got thisfrom my dad. Its kind of just been likeme.

But what she didn't know was that shehad an identical twin sister who lived

just miles away in New York City.

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Adoption Studies June 18, 2004

Researcher Nancy Segal hasspent a lifetime trying to answerquestions. She has interviewedmore than 50 pairs of identicaltwins who were separated at birth.

"Identical twins raised apart areexceedingly rare," says Segal."they're very, very valuable casesto scientists."

She wants to know how Tamaraand Adriana's similarities comparewith other identical twins

separated at birth. What can theyteach us about why we behavethe way we do? Why we pickcertain jobs? Why we have certainfriends?

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"To the extent that identical twinsare more alike in these things, wecan say with a fairly strong degreeof confidence that yes, genes doplay a role," says Segal.

So, does it really matter what youdo as a parent? Long-rangestudies of identical twins show thatparenting is important because itaffects how well your child willdevelop their genetic potential.

We find that genes play a 50

percent role in fashioningpersonality, which means that halfis also fashioned by theenvironment, says Segal.

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The twins show some verystriking similarities in personality,but when you look at personalitydevelopment across a broaderspectrum of people, you will findsome differences.

Whatever the differences betweenAdriana and Tamara are, its theirsimilarities that matter most tothem.

I just feel like Ive known her mywhole life. I just feel so

comfortable and theres just somuch familiarity with her that itsstrange, says Tamara. Evenwhen we walk together, I just feellike its right. Its just so strange.

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Since this story came outAdriana has graduatedfrom college with adegree in psychology.

Tamara expects tograduate soon with aminor in psychology.

(this story is documentedon the CBS new web siteunder the heading Twist

of fate if you want toread more about theirstory).

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Reaction range

Reaction range is the

range of potential

expressions of a

hereditary trait. Forexample body size

which is regulated by

biological factors can

be influenced within a

range based onenvironmental factors.

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Genotype Environment

interaction the reactions of genetically different people

to similar environmental conditions in

other words sometimes a trait requires both

a genetic predisposition and anenvironmental condition. The example used

in your textbook is allergies to pollen (pg 82)

People with pollen allergies have to have

both a genetic predisposition to be allergicas well as the environmental influences of

pollen

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Genotype-Environment

Correlation Genotype-Environment

Correlation Theenvironment reinforcescertain genetic differences.This can work in one of3

ways Passive correlations:

Parents who have providedthe gene also provide anenvironment where that traitis encouraged. This could

work in the obesity exampleused earlier, or in musical orartistic talent.

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Genotype-Environment

Correlation Reactive or Evocative

Correlations: Childrensdifferent geneticmakeup can evoke

different responsesfrom parents and sothey set up theenvironment different toaccommodate those

children and this elicitsa response from thechild which strengthensa genetic predisposition

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Active Correlations

Active Correlations: This is also called

niche-pickingand it is a tendency of a

person to seek out environments that

are compatible with their own

genotypes. For example a child who

has musical or artistic tendencies

would choose activities and extra curricular classes in those areas which

in turn strengthen the predisposition.

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The Non-Shared environment

Children within families

are often very different

even though one would

think they share the

same environment.

Closer observation of

the family would reveal

that there are many

environmentaldifferences which affect

each child individually.

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The Non-Shared environment

These aspects are:family compositionand birth order

Parental differentialtreatment

Illnesses

Accidents

Peers/teachers Experiences outside

the home

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GP5 What role do heredity and

environment play in physicalhealth, intelligence and

personality?

As weve discussedsome

characteristics are

influenced by both

hereditary andgenetics.

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GP5 What role of heredity andenvironment

There are geneticpredispositions but

environmental

conditions will

influence whether ornot a child is obese

for example

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Intelligence

Heredity indicates a

strong influence on IQ

however prenatal care,early childhood

experiences, family

literacy and parental

care can have an effect

on to what extent IQ isdeveloped.

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Intelligence

Heredity indicates a

strong influence on IQ

however prenatal care,early childhood

experiences, family

literacy and parental

care can have an effect

on to what extent IQ isdeveloped.

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Personality

Many aspects ofpersonality areinherited (inborn)

For exampleshyness orboldness. Howeverparental handlingcan lead innately

shy children to bemore outgoing orvice versa.

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Personality

Psychopathology There isstrong evidence for heredityinfluences on schizophrenia,autism, alcoholism, anddepression.

However heredity alonedoes not cause theseconditions it just meansthat some people based onenvironmental factors theymight experience will have a

greater predisposition tothese conditions

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6. What are the 3 stages of

prenatal development andwhat happens during each

stage?

Prenatal development takes part in 3stages which will be discussed

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2 principles of development are

important to understand before

discussing the stages

Cephalocaudal

(head to toe)

embryonic /fetaldevelopment occurs

largely from head to

toe

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2 principles of development are

important to understand before

discussing the stages

And proximodistal

(near to far)

meaningdevelopment

proceeds from

centre of body to

outer parts such asfingers and toes.

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3 stages of prenatal development

Germinal stageDuring the germinalstage, which begins

at conception andlasts approximately 2weeks; the zygote(the one celledorganism formed by

the unification ofsperm and ovum)cells divide rapidly.

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This growing mass of cells travels through

the mother's fallopian tube to the uterus.there, it becomes embedded into the

uterine lining and the placenta is formed.

The placenta surrounds and protects the

zygote and brings in nutrients and oxygen

while removing wastes.

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Embryonic Stage

Period of about 2-8

weeks characterized

by rapiddevelopment of

organs major body

systems

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In the picture, tenmodels, approximatelylife-sized, representeight weeks ofembryonicdevelopment, at the endof which main organsystems, limbs andfeatures have takenshape.

T

here are 3 stages theFETAL stage isdiscussed in GP7 (nextlecture) The end

chapter 3 gp 4,5 & 6

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