What is cognitive development?
Developmental psychology = The scientific study of biological, cognitive, social, and personality development
throughout the life span
What are the stages of development?
What is cognition?
Cognition = acquisition, processing, storage, and acting on information from the environment
A major issue in developmental psychology is the nature-versus-nurture question
Longstanding controversy over the relative contributions that genes and experience make to the development of
psychological traits and behaviors
Traits and behaviors arising from the interaction of nature vs nurture
Why are “Nature vs Nurture” Important?
Nature vs nurture is a classic debate in psychology
The outcome of the nature vs nurture argument has significant implications for understanding:
Raises arguments such as why we are different despite having the same DNA
Why do we behave as we do situations? (Inferring to nature and nurture)
Predicting characteristics (our strengths, weaknesses, and potential)
Nature:
Nature is our genes
A gene is a physical and functional segment of deoxyribonucleic acid (DNA)
The Human Genome estimated that humans have between 20,000 and 25,000 genes
Genes have different forms called ‘alleles’ located at the same place (genetic locus – loci) on a chromosome
Alleles are the cause/ form of genetic variability as they have small differences in DNA
Depending on type they have small differences in DNA (large difference in coding of phenotype)
Humans are diploid organisms, so they have two alleles at each genetic locus (one inherited from each
parent)
Each pair of alleles represents the genotype of a particular gene
Genes are homozygous if there are two identical alleles at a particular locus and heterozygous if the two alleles are
different
Gene alleles can either be dominant or recessive
Reproduction creates genotypic variation by reassembling alleles into combinations (less than 1% of genes
differ in humans so, there is a huge case of heterogeneity)
The specific combination of alleles contributes to an organism’s phenotype (its outward appearance and
physiological traits)
Nature vs Nurture:
There is evidence that genetics determine physical traits (such as eye colour, hair colour etc), this is widely
accepted
Claims that psychological attributes (personality) are genetically predetermined are more controversial
The environment can determine is genotypic characteristics remain dormant or if they are shown
Can it really be the case that everything from personality to educational attainment to success in personal
relationships is genetically predetermined?
Probabilistic vs Deterministic:
Deterministic view = everything is encoded, even our academic potential, as it is hardwired from birth
Probabilistic view = that the way genes are expressed is strongly viewed from the environment (e.g., our
caregivers) may determine how our biology expresses itself
Genes determine our biological “blueprint” (e.g., cell growth/ development of the brain and nervous system), but
how that blueprint is expressed may be strongly influenced by the environment which it exists in.
Epigenetics:
,Study of how DNA interacts with the multitude of smaller molecules found within cells which can activate and de-
activate genes
Genes can be “turned off” and “turned on” depending on environmental experience
Genes are expressed when they are read and transcribed into RNA (during transcription) which is then
translated into proteins by ribosomes (translation)
Proteins are what determines a cells characteristics and function
Epigenetic reprogramming = epigenetic changes can survive cell division so they can affect organisms long-term
(evolution)
Epigenetic changes can lead to disease if they turn off a gene that makes a tumour- suppressing protein
Epigenetic changes can boost / interfere with transcription with specific genes (epigenome)
Epigenomes mediate lifelong dialogue between environment and genes, the chemical tags that can turn
genes on and off can be influenced by factors including diet, chemical exposure, and medication
Environmentally induced epigenetic changes are part of the reason why genetically identical twins can grow up to
have very different lives
As twins get older their epigenomes diverge, this affects the way they age and their susceptibility to disease
Social experiences can cause epigenetic changes (such as bullying)
Weaver et al (2004)
Found that when mother rats weren’t attentive enough to their pups, the genes in the babies that helped to
manage stress were methylated and turned off
Most epigenetic marks are erased when egg and sperm cells are formed, but research think that some of these
imprints survive and pass on the epigenetic traits onto the next generation
Epigenetic changes aren’t necessarily permanent, balanced lifestyle including a balanced diet, exercise, and
avoiding harmful contaminants may in the long run create a healthy epigenome
Epigenetic Evidence:
Caspi et al (2002)
Very important study in developmental psychology
Explored the relationship between genes and the environment (maltreatment) on behavioural development
Longitudinal study of criminality in New Zealand. Studies 1000 people from birth to adulthood.
They retained 96% of the sample after 26 years
Maltreatment during childhood increased the likelihood of becoming a violent offender, but did not
guarantee it
Other countless environmental and genetic factors may have influenced it (interplay between the two)
Hypothesised that the differences in the gene MAOA was associated with aggression
Low MAOA in conjunction with maltreatment significantly increased the likelihood of negative outcomes
Behavioural Genetics
Estimate the relative contributions of genes and environmental factors to behavioural variability through twin
studies
Studying twins helps us to document the relative influences of genes and environment on development
Monozygotic “identical” twins share 100% of the same alleles
Dizygotic “fraternal” twins share 50% of the same alleles
Twin studies employ two designs:
1. Keep home environments constant while varying genetic relatedness: monozygotic twins vs dizygotic twins
(both maintain home environments allows you to see varying genetic readiness and the similarity of genes)
2. Keep genetic relatedness constant while varying home environment (separate twins home environments into
two separate homes with different caregivers/ friendship groups/ cultures etc)
Minnesota Twin Project
Bouchard et al (1990)
Researchers at the university of Minnesota studied identical and fraternal twins for over 20 years
Over 100 sets of twins were reared apart (although they spent approximately 5 months together pre-
separation
Participants completed comprehensive batteries of medical and psychological assessments (intelligence,
personality, temperament, occupational and leisure interests, social attitudes etc)
R = measure of similarity
Findings:
Measures of intelligence had a very strong correlation despite separate environment in identical twins despite
separate environments (0.7)
Genes have an influence irrespective of environment
,Monozygotic twins reared apart are highly similar across many physical and psychological traits, despite
contrasting environmental experiences
Socio-economic status affects rate of cognitive development, but not final IQ (Bouchard 1999)
The average IQ correlation for adopted siblings is 0.30 in childhood, but this relationship may drop to 0 after
adolescence (due to epigenomes – Plomin & Daniels 2011)
Variability in genes, as opposed to the environment, explains how members of the same family can grow up to be
very different
Early environmental experiences can influence rate of development and similarity within adopted siblings,
but as they get older these can diverge
Evaluating Twin Studies:
Identical twins spend more time together than fraternal twins (this adds another dimension to their relationship
which isn’t accounted for within twin studies)
Prenatal environment may have a crucial influence on children’s development, and this is different for both
identical and fraternal twins
Identical twins are much more likely to have a shared social group over fraternal twins (peers have an important
influence on our development)
Peer Group Socialisation Theory
Judith Harris (1998)
Parents influence children’s development much less than is often claimed (e.g., Sigmund Freud)
Next to genetics, peer group is the next most significant influence on their development
Peer groups are more influential on our psychology than parents:
Electra Complex = psychoanalytic term to describe a girl’s sense of competition with her mother for the
affections of her father
Oedipus Complex = psychoanalytic theory that there is a desire for sexual involvement with the parent of
the opposite sex, and a concomitant sense of rivalry with the parent of the same sex (crucial stage in
normal development process)
Sigmund Freud introduced the concept in his Interpretation of Dreams (1999)
Complexity Theory = The study of complex and chaotic systems and how, order, pattern and structure can arise
from them
The theory that processes having many seemingly independent agents can spontaneously order themselves into a
coherent system
Children and adults show context-specific behaviour (we act differently depending on who we are with and where
we are, such as different behaviours and actions)
Children get older the “outside behavioural system” is more influential on their personality than their in-
home behaviour
Children identify with their peers, rather than adults, and therefore try to be successful within their peer
group to establish themselves
Peer groups develop their own culture, which can contrast with adult demands
Peer group in middle-childhood and adolescence shapes an individual’s personality in ways that endure
into childhood
Within-group processes make children more similar (e.g., conformity) and more different (e.g., hierarchies)
to one another
Peers (Aristotle)
Stereotypes (adolescents take risks)
Smoking, drinking, drugs, and dangerous driving all take place when with friends (under the influence of
peers)
Gardner and Steinberg (2005)
Observed adolescents whilst playing video games with friends
Found that adolescents increase their risk-taking behaviours in a driving video game when in the presence
of peers
Number of risks is the same regardless of age when playing alone, but increases in adolescents when
playing with friends
Cohen and Prinstein (2006)
Found that adolescents increase their maladaptive responses to hypothetical scenarios involving deviant
and health- risk behaviours, after being exposed to the risky responses of experimentally manipulated
“peers” in a simulated “internet chat room”
Social influence on risk-perception (rate how risky everyday situations are) age 12-14 are the more
influenced by their own age than both children and adults
Catherine Sebastian
, Adolescent hyper acceptance
Campaigns work when those their age create and deliver the campaigns as opposed to adults (e.g., save
the environment talks, anti-smoking etc)
The brain develops during adolescence therefore everything is unstable (brain and hormones),
This is the most critical adaptive development period
Evaluating Peer Group Socialisation:
Difficult to test the direction of effects (e.g., a genetically studious child is more likely to join a studious
peer group / circle of friends)
Parents can have an influence on who a child is friends with (Durbin et al, 1993)
Parents and peers may have influences in different contexts
Children may behave differently in different settings
The relative influence of parents and peers may be interdependent (e.g., no support at home so friends are
more supportive, hence them having a larger influence)
Explanation of Human conception?
Human conception:
Stage 1:
When a sperm penetrates the membrane of an ovum
The two combines = a complete set of genetic instructions is formed, half from the father and half from the mother
The fertilized egg that is formed is called a zygote
Stage 2:
Germinal state the one-cell zygote starts to divide into two and then into 4 and so for until birth
Stage 3:
The embryonic period that the cells start to group and form the blastocyst from which:
Endoderm (layer of cells that will form the internal organs),
Mesoderm (layer of cells that will form the skeletal muscles)
Ectoderm (layer of cells that will form the skin and nervous system) will develop
The fetal period starts two months after conception and lasts until birth
This figure shows the different fetal stages:
Four weeks after fertilisation = brain begins to form.
Whilst developing babies receive postcards from the outside world = these postcards tell us if this world is
dangerous or safe
Month 1:
Every bit of genetic information is already present in a single cell = divide again and again
After a week = travel from the ovaries to the uterus where Mitosis occurs, splitting into two, half is the baby while
the other half forms the placenta which brings food, oxygen and carries away waste.
By week four = developed into a small being that is growing at a rate of 1 million cells per second
Our spinal cord, heart and brain are now clearly visible
Month 2:
Developmental psychology = The scientific study of biological, cognitive, social, and personality development
throughout the life span
What are the stages of development?
What is cognition?
Cognition = acquisition, processing, storage, and acting on information from the environment
A major issue in developmental psychology is the nature-versus-nurture question
Longstanding controversy over the relative contributions that genes and experience make to the development of
psychological traits and behaviors
Traits and behaviors arising from the interaction of nature vs nurture
Why are “Nature vs Nurture” Important?
Nature vs nurture is a classic debate in psychology
The outcome of the nature vs nurture argument has significant implications for understanding:
Raises arguments such as why we are different despite having the same DNA
Why do we behave as we do situations? (Inferring to nature and nurture)
Predicting characteristics (our strengths, weaknesses, and potential)
Nature:
Nature is our genes
A gene is a physical and functional segment of deoxyribonucleic acid (DNA)
The Human Genome estimated that humans have between 20,000 and 25,000 genes
Genes have different forms called ‘alleles’ located at the same place (genetic locus – loci) on a chromosome
Alleles are the cause/ form of genetic variability as they have small differences in DNA
Depending on type they have small differences in DNA (large difference in coding of phenotype)
Humans are diploid organisms, so they have two alleles at each genetic locus (one inherited from each
parent)
Each pair of alleles represents the genotype of a particular gene
Genes are homozygous if there are two identical alleles at a particular locus and heterozygous if the two alleles are
different
Gene alleles can either be dominant or recessive
Reproduction creates genotypic variation by reassembling alleles into combinations (less than 1% of genes
differ in humans so, there is a huge case of heterogeneity)
The specific combination of alleles contributes to an organism’s phenotype (its outward appearance and
physiological traits)
Nature vs Nurture:
There is evidence that genetics determine physical traits (such as eye colour, hair colour etc), this is widely
accepted
Claims that psychological attributes (personality) are genetically predetermined are more controversial
The environment can determine is genotypic characteristics remain dormant or if they are shown
Can it really be the case that everything from personality to educational attainment to success in personal
relationships is genetically predetermined?
Probabilistic vs Deterministic:
Deterministic view = everything is encoded, even our academic potential, as it is hardwired from birth
Probabilistic view = that the way genes are expressed is strongly viewed from the environment (e.g., our
caregivers) may determine how our biology expresses itself
Genes determine our biological “blueprint” (e.g., cell growth/ development of the brain and nervous system), but
how that blueprint is expressed may be strongly influenced by the environment which it exists in.
Epigenetics:
,Study of how DNA interacts with the multitude of smaller molecules found within cells which can activate and de-
activate genes
Genes can be “turned off” and “turned on” depending on environmental experience
Genes are expressed when they are read and transcribed into RNA (during transcription) which is then
translated into proteins by ribosomes (translation)
Proteins are what determines a cells characteristics and function
Epigenetic reprogramming = epigenetic changes can survive cell division so they can affect organisms long-term
(evolution)
Epigenetic changes can lead to disease if they turn off a gene that makes a tumour- suppressing protein
Epigenetic changes can boost / interfere with transcription with specific genes (epigenome)
Epigenomes mediate lifelong dialogue between environment and genes, the chemical tags that can turn
genes on and off can be influenced by factors including diet, chemical exposure, and medication
Environmentally induced epigenetic changes are part of the reason why genetically identical twins can grow up to
have very different lives
As twins get older their epigenomes diverge, this affects the way they age and their susceptibility to disease
Social experiences can cause epigenetic changes (such as bullying)
Weaver et al (2004)
Found that when mother rats weren’t attentive enough to their pups, the genes in the babies that helped to
manage stress were methylated and turned off
Most epigenetic marks are erased when egg and sperm cells are formed, but research think that some of these
imprints survive and pass on the epigenetic traits onto the next generation
Epigenetic changes aren’t necessarily permanent, balanced lifestyle including a balanced diet, exercise, and
avoiding harmful contaminants may in the long run create a healthy epigenome
Epigenetic Evidence:
Caspi et al (2002)
Very important study in developmental psychology
Explored the relationship between genes and the environment (maltreatment) on behavioural development
Longitudinal study of criminality in New Zealand. Studies 1000 people from birth to adulthood.
They retained 96% of the sample after 26 years
Maltreatment during childhood increased the likelihood of becoming a violent offender, but did not
guarantee it
Other countless environmental and genetic factors may have influenced it (interplay between the two)
Hypothesised that the differences in the gene MAOA was associated with aggression
Low MAOA in conjunction with maltreatment significantly increased the likelihood of negative outcomes
Behavioural Genetics
Estimate the relative contributions of genes and environmental factors to behavioural variability through twin
studies
Studying twins helps us to document the relative influences of genes and environment on development
Monozygotic “identical” twins share 100% of the same alleles
Dizygotic “fraternal” twins share 50% of the same alleles
Twin studies employ two designs:
1. Keep home environments constant while varying genetic relatedness: monozygotic twins vs dizygotic twins
(both maintain home environments allows you to see varying genetic readiness and the similarity of genes)
2. Keep genetic relatedness constant while varying home environment (separate twins home environments into
two separate homes with different caregivers/ friendship groups/ cultures etc)
Minnesota Twin Project
Bouchard et al (1990)
Researchers at the university of Minnesota studied identical and fraternal twins for over 20 years
Over 100 sets of twins were reared apart (although they spent approximately 5 months together pre-
separation
Participants completed comprehensive batteries of medical and psychological assessments (intelligence,
personality, temperament, occupational and leisure interests, social attitudes etc)
R = measure of similarity
Findings:
Measures of intelligence had a very strong correlation despite separate environment in identical twins despite
separate environments (0.7)
Genes have an influence irrespective of environment
,Monozygotic twins reared apart are highly similar across many physical and psychological traits, despite
contrasting environmental experiences
Socio-economic status affects rate of cognitive development, but not final IQ (Bouchard 1999)
The average IQ correlation for adopted siblings is 0.30 in childhood, but this relationship may drop to 0 after
adolescence (due to epigenomes – Plomin & Daniels 2011)
Variability in genes, as opposed to the environment, explains how members of the same family can grow up to be
very different
Early environmental experiences can influence rate of development and similarity within adopted siblings,
but as they get older these can diverge
Evaluating Twin Studies:
Identical twins spend more time together than fraternal twins (this adds another dimension to their relationship
which isn’t accounted for within twin studies)
Prenatal environment may have a crucial influence on children’s development, and this is different for both
identical and fraternal twins
Identical twins are much more likely to have a shared social group over fraternal twins (peers have an important
influence on our development)
Peer Group Socialisation Theory
Judith Harris (1998)
Parents influence children’s development much less than is often claimed (e.g., Sigmund Freud)
Next to genetics, peer group is the next most significant influence on their development
Peer groups are more influential on our psychology than parents:
Electra Complex = psychoanalytic term to describe a girl’s sense of competition with her mother for the
affections of her father
Oedipus Complex = psychoanalytic theory that there is a desire for sexual involvement with the parent of
the opposite sex, and a concomitant sense of rivalry with the parent of the same sex (crucial stage in
normal development process)
Sigmund Freud introduced the concept in his Interpretation of Dreams (1999)
Complexity Theory = The study of complex and chaotic systems and how, order, pattern and structure can arise
from them
The theory that processes having many seemingly independent agents can spontaneously order themselves into a
coherent system
Children and adults show context-specific behaviour (we act differently depending on who we are with and where
we are, such as different behaviours and actions)
Children get older the “outside behavioural system” is more influential on their personality than their in-
home behaviour
Children identify with their peers, rather than adults, and therefore try to be successful within their peer
group to establish themselves
Peer groups develop their own culture, which can contrast with adult demands
Peer group in middle-childhood and adolescence shapes an individual’s personality in ways that endure
into childhood
Within-group processes make children more similar (e.g., conformity) and more different (e.g., hierarchies)
to one another
Peers (Aristotle)
Stereotypes (adolescents take risks)
Smoking, drinking, drugs, and dangerous driving all take place when with friends (under the influence of
peers)
Gardner and Steinberg (2005)
Observed adolescents whilst playing video games with friends
Found that adolescents increase their risk-taking behaviours in a driving video game when in the presence
of peers
Number of risks is the same regardless of age when playing alone, but increases in adolescents when
playing with friends
Cohen and Prinstein (2006)
Found that adolescents increase their maladaptive responses to hypothetical scenarios involving deviant
and health- risk behaviours, after being exposed to the risky responses of experimentally manipulated
“peers” in a simulated “internet chat room”
Social influence on risk-perception (rate how risky everyday situations are) age 12-14 are the more
influenced by their own age than both children and adults
Catherine Sebastian
, Adolescent hyper acceptance
Campaigns work when those their age create and deliver the campaigns as opposed to adults (e.g., save
the environment talks, anti-smoking etc)
The brain develops during adolescence therefore everything is unstable (brain and hormones),
This is the most critical adaptive development period
Evaluating Peer Group Socialisation:
Difficult to test the direction of effects (e.g., a genetically studious child is more likely to join a studious
peer group / circle of friends)
Parents can have an influence on who a child is friends with (Durbin et al, 1993)
Parents and peers may have influences in different contexts
Children may behave differently in different settings
The relative influence of parents and peers may be interdependent (e.g., no support at home so friends are
more supportive, hence them having a larger influence)
Explanation of Human conception?
Human conception:
Stage 1:
When a sperm penetrates the membrane of an ovum
The two combines = a complete set of genetic instructions is formed, half from the father and half from the mother
The fertilized egg that is formed is called a zygote
Stage 2:
Germinal state the one-cell zygote starts to divide into two and then into 4 and so for until birth
Stage 3:
The embryonic period that the cells start to group and form the blastocyst from which:
Endoderm (layer of cells that will form the internal organs),
Mesoderm (layer of cells that will form the skeletal muscles)
Ectoderm (layer of cells that will form the skin and nervous system) will develop
The fetal period starts two months after conception and lasts until birth
This figure shows the different fetal stages:
Four weeks after fertilisation = brain begins to form.
Whilst developing babies receive postcards from the outside world = these postcards tell us if this world is
dangerous or safe
Month 1:
Every bit of genetic information is already present in a single cell = divide again and again
After a week = travel from the ovaries to the uterus where Mitosis occurs, splitting into two, half is the baby while
the other half forms the placenta which brings food, oxygen and carries away waste.
By week four = developed into a small being that is growing at a rate of 1 million cells per second
Our spinal cord, heart and brain are now clearly visible
Month 2:
