The Nature and Nurture of
Behavior
•
•
•
•
•
Genes
Explaining Similarity
Explaining Differences
Environmental Differences
Gender
1
2
3
4
The Human Cell
• The human body is comprised of over 200
different kinds of cells which are the smallest selfcontained structures
– Cell membrane: the outside layer of the cell
– Cytoplasm: is comprised of specialized structures
– Mitochondria: are the powerhouses that process
nutrients and provide the cell’s energy
– Endoplasmic reticulum, Golgi apparatus, and
ribosomes: produce proteins
– Neucleus: The inner part of the cell
5
The Nucleus
• Chromosomes
• Genes
• Deoxyribonucleic acid (DNA)
6
Chromosomes
• Rod shaped structures found in the center of
the nucleus of every cell in the body.
• Each sperm and each ovum contains 23
chromosomes.
• The chromosomes contain the genes.
• The fertilized egg (zygote) and all the body cells
that develop from it (except the sperm cells and
the ova) contain 46 chromosomes.
7
Karyotype
A photograph of a cell’s chromosomes
arranged in pairs according to size
8
Genes
• The basic unit of genetic information
• They determine the nature and the function
of the cell.
• The human genes (about 140,000) are
referred to as the human genome.
• A genome is the full set of genes in each
cell of an organism.
9
A Portion of a DNA Molecule
10
DNA
• They determine the nature of each cell
and how it will function.
• At each level of the spiral or rungs of the
ladder are particular chemical pairs. The
arrangement of these pairs along the
DNA molecule determines which kind of
proteins that will be formed in the cell.
11
Terms
• Gametes:
Sex cells (ovum or sperm)
• Diploid cells:
Cells having 2 copies of each chromosome
• Haploid gametes:
Gametes having 1 copy of each chromosome
12
Meiosis
• Meiosis takes place in the testicles and ovaries.
• A diploid cell (having 2 copies of each
chromosome) undergoes a special form of cell
division to create haploid gametes (having 1 copy
of each chromosome).
• An egg and a sperm fuse together to form a new
diploid cell called zygote (a process called
fertilization)
13
14
Mitosis
• In the first step of mitosis, all chromosomes are
copied, so that instead of 2 copies, the cell briefly
has 4 copies of each chromosome.
• Shortly afterwards, the cell divides in half,
resulting in two cells each has a complete copy of
the genetic information.
• These cells grow larger and eventually undergo
mitosis.
15
16
Gregor Mendel (1800s)
17
Genotype
The genetic makeup of a
given individual
Recessive Gene
The gene pair that
determines a trait in an
individual only if the
other member of that
pair is also recessive
Phenotype
The traits that are
expressed in the
individual
Dominant Gene
One gene of a gene pair
that will cause a
particular trait to be
expressed
18
19
Stop and Discuss
•
•
•
•
•
•
•
Gametes
Zygote
Monozygotic twins
Dizygotic twins
Diploid cells
Haploid gametes
Genome
•
•
•
•
•
•
•
Chromosomes
Genes
DNA
Meiosis
Mitosis
Phenotype
Genotype
20
Celera Genomics Project
The Human Genome Project
• In June 26, 2000, they both made an
announcement that the “correct alphabetical
order of the 3.12 billion letters” of the
human genome had been mapped.
• It will be many years before the incredibly
complex functions of the genome in making
and maintaining a living human being are
fully understood.
21
Genetic Engineering
• Alteration of Human Genes
• 1- Gene Therapy
• 2- Germ-line Genetic Alterations
Germ-line Genetic Intervention
• 3- Genetic Enhancement
22
1- Gene Therapy
• Genetic alteration of somatic cells to treat
disease.
• Researchers inject genes that are targeted to
treat a particular disease in to a patient’s
blood stream.
• When the genes arrive at the site of the
defective genes, they produce chemicals
that can treat the problem.
23
2-Germ-line Genetic Alteration
• Can correct problems for unborn individuals and
future generations.
• It targets the genes in the reproductive cells – the egg
and the sperm that combine the DNA to conceive a new
human.
• Scientist might detect defective cells soon after
conception, removing them from the mother and
placing them in a test-tube culture.
• Gene therapy could be employed to correct the defects
in the cells.
• The result could be cloning. Parents could some day
customize their children.
24
3-Genetic Enhancement
• Non therapeutic genetic alteration
• An attempt to enhance an already healthy
genetic makeup by inserting a gene for
improvement (e.g. height, intelligence, eye
color)
25
Cloning
• Producing genetic replicas of
the organism
26
What Do You Think?
Genetic Engineering
Gene Therapy
Germ-Line Genetic
Alterations
Genetic enhancement
27
Stop and Discuss
• In your opinion, how ethical are these
issues?
1- Gene therapy
2- Germ-line genetic alteration
3- Genetic enhancement
4- Cloning
28
Universal Behaviors
Evolutionary Psychology
Evolution
The process through which species change across
generations
Evolutionary Psychology
The study of inherited psychological
characteristics.
Natural Selection
The traits that contribute to reproduction and
survival will most likely be passed on to
succeeding generations.
29
Universal Behaviors
Evolutionary Psychology
Mutation
A random error in gene replication that leads
to a change in the sequence of nucleotides;
the source of all genetic diversity.
Sexuality
30
David Buss
and the International Team
(1994)
• 50 scientists studied:
10,000 people
in 37 cultures
in 6 continents
31
Human Sex Differences Are
Universal
•
•
•
•
Males
Promiscuous
Undiscriminating
Competitive and
concerned about
dominance
• Prefer beauty and
health
• Like sexual novelty
•
•
•
•
Females
Devoted and faithful
Cautious
Less competitive
• Prefer resources and
social status
• Like stability and
security
32
Innate Human Characteristics
• Infant Reflexes
• An Attraction to Novelty
• A Desire to Explore and manipulate objects
• An Impulse to play and Fool Around
• Basic Arithmetic Skills
33
Language Acquisition Device
Innate Mental Module
Noam Chomsky
• Children in different cultures go through
similar stages of linguistic development.
• Children combine words in ways adults
never do.
• Adults don’t consistently correct their
children’s syntax.
• Even retarded children develop language.
• Infants can derive simple linguistic rules.
34
Explaining Differences
Behavior Genetics
Behavior Genetics
• The study of the relative power and limits
of genetic and environmental influences on
behavior
35
Twin Studies
• 13,000 pairs of Swedish twins, 7000 Finnish
twin pairs, 3810 Australian twin pairs
Identical twins are more similar than fraternal twins
on both extroversion & neuroticism
• Battery of questionnaires to 850 U.S. twins
Identical twins are more similar in abilities,
personality traits, & interests.
Reported being treated alike
36
Separated Twins
• The Jim Twins
Similar in:
brain waves
voice intonation
interests
heart rate
personality
intelligence
37
Adoption Studies
• People who grow up together, whether
biologically related or not, do not much
resemble one another in personality.
• Adoptees’ traits bear more similarities to
their biological parents than to their caregiving adoptive parents
38
Temperament Studies
Traits such as
excitability – whether the baby is intense,
reactive, fidgety, easy going, or quiet
tend to remain steady in later years
39
Group Differences
Of our genetic differences
– Only 6% are among races
– Only 8% are differences among groups
within a race
– The rest – over 85% - are individual
variations within local groups
– Some traits are highly heritable:
• Weight, height, and intelligence
40
The “Obese” Gene
• Obese gene causes fat cells to produce
leptin.
• Leptin travels through blood to
hypothalamus (regulates appetite)
• Leptin reduces appetite
41
The Function of the Protein
Leptin
• Reduces appetite
• Speeds up metabolism
• Makes people more active
42
Why Do People Gain Weight
Rapidly?
• Secretion of leptin is impaired
• May produce plenty of leptin but
their body does not respond to it.
• Tendency to store calories which
have a survival advantage.
43
44
45
46
Gene-Environment Interaction
“Heredity deals the cards;
environment plays the hand.”
Psychologist Charles L. Brewer
(1990)
47
Environmental Influence
•
•
•
•
•
Prenatal Environment
Experience and Brain Development
Peer Influence
Culture
Gender
48
Prenatal Care
•
•
•
•
•
•
•
Diet
The father’s involvement
Age of mother
Illness of mother
Drug use
Alcohol
Teratogens
49
Experiences and Brain Development
• Rosenzweig and Krech’s experiment on
rats:
– Those living in the enriched environment
developed a thicker and heavier brain cortex.
– Experience preserves our activated
connections while allowing the unused
connections to degenerate
Use it or lose it
50
Parents and Peers are Complementary
Howard Gardner (1998)
“Parents are more important when it comes to
education, discipline, responsibility, orderliness.
Charitableness, and ways of interacting with
authority figures. Peers are more important for
learning cooperation, for finding the road to
popularity, for inventing styles of interaction
among people of the same age. Youngsters may
find their peers more interesting, but they will
look to their parents when contemplating their
own futures.”
51
Relationships with Peers
1- Peers Provide the opportunity to
compare and evaluate opinions, abilities,
and physical changes – a process called
social comparison
2- Peers may serve as a reference groups –
groups of people with whom one
compares oneself.
52
Culture
• Variation Across Cultures
• Variation Over Time
• Culture and Child Rearing
53
Gender
• The Nature of Gender
– X chromosome
– Y chromosome
– Testosterone
• The Nurture of Gender
– Gender role
54
What Is the Role of Parenting?
1- Do parents really produce future adults with a
wounded child within by being irresponsible?
2- Should we blame our parents for our failings?
3- Should we shame the parents of troubled
children?
4- Should parents be given less credit for children
who turn out great?
5- What is the role of parents?
55