PSYC1003 Lecture Notes - Lecture 8: Aspirin, Joint Attention, Essentialism
Biological and Cognitive Development
Biology and developmental psychology- prenatal development
Genetic foundations
oThere is natural variation in the human population
oGenetics is the ‘nature’ side of the Nature-Nurture debate
oPsychology interfaces with genetics
oGenotype + environment = phenotype
oOn each chromosome there are sets of genes which code for organism
functions either in isolation or through interaction with other genes
(polygenic inheritance)
Dominant disorder: Huntington Disease
oNervous system deterioration after the age of 40
oAll carriers develop the disease
oIt hasn’t died out become by the time it shows in an individual they have
already reproduced and passed on the genes
oWhen someone suspects they might have it genetics tests are done, and
psychologists are involved
Recessive disorder: Phenylketonuria (PKU)
oInability to metabolise phenylalanine, an amino acid found in food
oPhenylalanine accumulates in blood, causing severe cognitive deficits and
other abnormalities
oNewborns are screened at birth, avoidance of phenylalanine results in typical
development- genetic-environment interaction
Chromosomal abnormalities
oErrors in cell division during gamete formation
oDown syndrome (trisomy 21)
Low IQ
Memory and speech problems
Limited vocab
Motor problems
Congenital eye, ear, heart and intestinal defects
More common in older mothers
Syndrome Typical characteristics Incidence
Turner’s syndrome
(XO)
Female, short, webbed neck,
heavy build, infertile, poor
memory and spatial ability
1 in 5000
Poly-X syndrome
(XXX)
Female, tall, fertile, impaired
verbal intelligence
1 in 1000
Klinefelter’s (XXY) Male, very tall, sterile, female
body type with low male
hormone level, impaired
verbal intelligence
1 in 900
XYY syndrome Male, tall, fertile, near-
normal intelligence
1 in 1000
Polygenic inheritance
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oVariables of interest to developmental psychologists are not typically
determined by singular genetic abnormalities
oThey implicate complex interactions between sets of genes
Behavioural genetics
oAims to determine the contributions
oHeritability: the proportion of a given behaviour that is due to genetics
rather than environmental factors
Natural experiments which allow us to tease apart genetics from environment
oTwin studies
Identical (monozygotic) twins
Splitting of a single fertilised egg
Same DNA
Same environment
Fraternal (dizygotic) twins
Separate fertilisation of two eggs
Different DNA
Same environment
Identical twins–fraternal twins=(genetic + environment)-environment
If identical twins are more similar on a given behaviour than fraternal
twins, then that behaviour has a heritable component
H= 2 [ r (identical)- r (fraternal) ]
Problem: each twin may not share the same environment- it is
altered by their identity
People treat identical twins and expect them to behave more
similarly
oAdoption studies
Produces two conditions important for behavioural genetics
Family members share same environment, different genetics
Family members who share genetics, but not environment
Leads to three comparison groups
Genetics + environment
Shared environment
Shared genetics
Typically show similarities due to both genetics and environment
Problems
Generalisability: adoptive parents, biological parents, and
adopted children are not representative of the population
Common pre-natal environment of adopted children and
their non-adopted siblings may account for similarities, not
genetics
Adoption agencies have tended to ‘match’ children to
families of similar background- influence on environment
Prenatal development
oMost rapid and dramatic period of change across the lifespan
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Chromosomal abnormalities: errors in cell division during gamete formation, down syndrome (trisomy 21) Congenital eye, ear, heart and intestinal defects. Female, short, webbed neck, heavy build, infertile, poor memory and spatial ability. Male, very tall, sterile, female body type with low male hormone level, impaired verbal intelligence. 1 in 1000: variables of interest to developmental psychologists are not typically determined by singular genetic abnormalities, they implicate complex interactions between sets of genes. Behavioural genetics: aims to determine the contributions, heritability: the proportion of a given behaviour that is due to genetics rather than environmental factors. Natural experiments which allow us to tease apart genetics from environment: twin studies. If identical twins are more similar on a given behaviour than fraternal twins, then that behaviour has a heritable component. H= 2 [ r (identical)- r (fraternal) ] Problem: each twin may not share the same environment- it is altered by their identity.
