What’s it all about?
• Nature = Behaviours, motivation,
emotions, etc, that are essentially
biological and that we were born with
(inherited).
• Nurture = Behaviours, etc, that are
essentially learnt and therefore were not
born with. (This learning is known as early
socialisation.)
Imprinting
Baby ducks will follow the first thing see after they are born
Thinking it is their mother.
DNA
• Most human beings have 23 pairs of chromosomes
so 46 in total.
• 23rd chromosome determines sex
• Chromosome contain our DNA which determines all
of our characteristics.
What does DNA determine about us?
• To a degree: Everything.
• Down Syndrome babies have 47 chromosomes. An
extra 21st chromosome
Most individuals who have Down syndrome have intelligence
quotient (IQ) scores in the mild to moderate range of retardation.
Children with Down syndrome need to be in special educational
programs that give them a good environment for learning and that
keep pace with their intellectual capabilities.
Nature vs. Nurture in IQ
• Are differences between people due to
environmental or genetic differences?
• Misunderstanding the question
– “Is a person’s intelligence due more to genes or to
environment?”
– no genes = no intelligence
– both genes & intelligence crucial for any trait
Study Techniques
• Twin Research
– Identical versus fraternal twins (monozygotic
versus dizygotic)
– Shared environmental experiences
• Common experiences, e.g. parent’s personality,
intelligence, SES status, neighborhood live in, parenting
techniques
– Nonshared environmental experiences
• Child’s own experiences within and outside the family
that are not shared with siblings
Twins
Genetic Influences
Similarity of 1.0
intelligence 0.9
scores 0.8
(correlation) 0.7
• The most
genetically
similar people
have the most
similar scores
0.6
0.5
0.4
0.3
0.2
0.1
0.0
Identical
twins
reared
together
Identical
twins
reared
apart
Fraternal
twins
reared
together
Siblings
reared
together
Unrelated
individuals
reared
together
Family Influence on IQ
– adoptive siblings as
children and adults
– identical vs. fraternal
twins reared together
1
Correlation coefficient
• Transient
influence of
family in which
you are raised
Identical twins
0.8
Fraternal twins
0.6
0.4
0.2
0
4-5
6-11 12-15 16-19 Adult
Age group
IQ Differences among
Racial/Cultural Groups
• Find differences among racial & cultural groups on
IQ
– American Blacks score about 15 points lower
than Whites
• WHY?
– genetics?
• Witty & Jenkins (1935)
• No support for genetic differences
– environment?
The study of Feral Children
• Wild children who have been separated from
society.
• The Case of Genie.
• Other cases.
Temperament & Personality
• Temperament: a set of tendencies to respond
in predictable ways.
• Buss & Plomin (1984) found .50 to .60 average
correlations between temperament scores of
identical twins. The correlations for fraternal
twins are about 0.
Raised apart, yet both grow up the same
Psychological Disorders
• Schizophrenia: disturbances in logical thinking,
emotional expression, social behavior.
• Originally: thought due to a cold and inconsistent
mother.
• Now: concordance rates for identical twins: 48%;
fraternal twins 17%.
• 1% of the general population has Schizophrenia.
Stages of Cognitive Development
Sensorimotor stage (Infancy). In this period (which has 6 stages), intelligence is
demonstrated through motor activity without the use of symbols. Knowledge of the world
is limited (but developing) because its based on physical interactions / experiences.
Children acquire object permanence at about 7 months of age (memory). Physical
development (mobility) allows the child to begin developing new intellectual abilities.
Some symbollic (language) abilities are developed at the end of this stage.
Pre-operational stage (Toddler and Early Childhood). In this period (which has two
substages), intelligence is demonstrated through the use of symbols, language use
matures, and memory and imagination are developed, but thinking is done in a nonlogical,
nonreversable manner. Egocentric thinking predominates
Concrete operational stage (Elementary and early adolescence). In this stage
(characterized by 7 types of conservation: number, length, liquid, mass, weight, area,
volume), intelligence is demonstarted through logical and systematic manipulation of
symbols related to concrete objects. Operational thinking develops (mental actions that
are reversible). Egocentric thought diminishes.
Formal operational stage (Adolescence and adulthood). In this stage, intelligence is
demonstrated through the logical use of symbols related to abstract concepts. Early in the
period there is a return to egocentric thought. Only 35% of high school graduates in
industrialized countries obtain formal operations; many people do not think formally
during adulthood.