HUMAN DEVELOPMENT 1 PSYCHOLOGY 3050
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Transcript HUMAN DEVELOPMENT 1 PSYCHOLOGY 3050
Fall, 2005
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HUMAN DEVELOPMENT 1
PSYCHOLOGY 3050:
Biological Bases of Cognitive Developement
Dr. Jamie Drover
SN-3094, 864-8383
e-mail – [email protected]
Winter Semester, 2013
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Evolution and Cognitive Development
Evolution: the process of
change in gene frequencies
in a population over many
generations that in time,
produces new species.
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Evolution and Cognitive Development
Based on natural selection.
Members of a species possess genetic variation.
Environmental conditions allow some species members to
survive and reproduce.
Their traits will be passed on, i.e., reproductive fitness.
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Evolution and Cognitive Development
Evolution provides a framework for interpreting all
aspects of behavior and development.
It explains the how and why aspects of behavior and
development.
How: natural selection
Why: it’s adaptive
Evolutionary Developmental Psychology: Explains
human development through evolutionary theory and
provide answers about adaptive fit to environment.
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Evolutionary Psychology
Cosmides and Tooby (1976) believe that natural
selection operates on the cognitive level.
Information-processing programs evolved cognitive
abilities to solve specific problems.
How to communicate, recognize faces
Cognitive processes develop and infants and children
face different problems than adults.
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Evolutionary Psychology
We evolved domain-specific mechanisms to deal with
specific aspects of the environment (face recognition,
language).
Note that domain-general mechanisms also evolved
due to natural selection.
Executive function: ability to inhibit thoughts and actions.
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Evolutionary Psychology
There are constraints (limitations) on development
Constraints enable (promote) learning
Infants born into a “chaotic” environment
Too much stimulation would inhibit (or delay) learning
Instead infants and children are constrained to process only
some information in core domains (e.g., language)
Can’t /don’t process everything; focus on “essentials”
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Evolutionary Psychology
Geary (2005) believes that we evolved a set of
domain-specific modules that develop as children
engage their physical and social worlds.
There are overarching social and ecological domains
with more specific domains (see Figure 2-1).
Despite these domain-specific modules, human
cognition is very flexible.
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Evolutionary Psychology
We did not evolve highly specific approaches to
problems but genes and cognitive mechanisms that
are highly adaptive.
These mechanisms become more specific and finely
tunes during development due to experience.
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Why does it take us so long to grow up?
Humans have an extended juvenile period
Longer than for any primate species
Provides the time needed to process and master
complex environments, provides “flexible cognition”.
Long “apprenticeship” to learn about a broad range of
environments
Requires a large brain
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Evolutionary Psychology
According to Geary (1995), we have two broad types
of cognitive abilities.
Biologically Primary Abilities: Selected for by evolution
(E.g., language)
Biologically Secondary Abilities: Cultural inventions (E.g.,
reading)
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Models of Gene-Environment Interaction
Developmentalists believe that development is the
result of an interaction between genetic/biological
factors and environmental/experiential factors.
the child is an active agent in his/her development
development proceeds through the bidirectional effect of
structure and function
context is as important as one’s genes.
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Developmental Systems Approach
Development occurs within a system of interacting
levels.
Our development is based on epigenesis.
Development is characterized by increasing complexity of
organization (the emergence of improved structures,
functions, and abilities) at all levels of the system. This
arises as a result of the interaction of all components of the
system.
Based on the bidirectional interaction of genes, RNA,
proteins, neurons, etc. with the environment.
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Developmental Systems Approach
Epigenetic phenomena do not involve changes to the
DNA code.
But it does involve change in the things that DNA
influences
RNA, proteins, cells, neurons, neurotransmitters.
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Developmental Systems Approach
Can’t understand development by looking at simple
genetic or environmental effects
Essentially dynamic systems approach applied to
development.
New structures and functions emerge through selforganization through bidirectional interactions of the
elements at various levels.
Implies plasticity in development
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Developmental Systems Approach
Research has indicated that there is a relationship
between breasfeeding and later IQ.
This may be due to essential fatty acids that exist in
breastmilk.
Caspi et al (2007) identified several variants of genes
that process these fatty acids.
One gene is obtained from the father, another is obtained
from the mother.
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Developmental Systems Approach
Children who are CC or CG and were breastfed as
infants had higher IQ than children with the same
alleles but were not breastfed.
Children with a third version of the genes (GG)
showed no effect on from being breastfed or bottlefed.
The benefits of breastfeeding for IQ are influenced by
combination of alleles that influence how fatty acids
are processed.
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Developmental Systems Approach
Why do species members develop in the species
typical pattern?
We inherit species-typical genes and a species typical
environment (see duck example, p 42).
Behavior is influenced by subtle aspects of the
environment.
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Developmental Systems Approach
• Humans develop in species-typical environments
(prenatal and postnatal)
– Experience directs us in species-typical ways.
• E.g., Development of hemispheric asymmetries.
– May be due to the timing of the nature of prenatal auditory
experiences (Turkewitz, 1993).
– Exposed to socially important sounds when the left
hemisphere of the brains is hitting a growth spurt.
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Developmental Systems Approach
Hemispheric asymmetries are due to an interaction
between genetically paced maturation and prenatal
species-typical experience.
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Developmental Timing
• Sensitive Period: A time in development when a skill
or ability is most easily acquired.
• If the required experience occurs outside this period,
it will not be easily acquired (or not acquired at all).
– Language (1st and second 2nd) are most easily acquired
during childhood.
• Overall, timing of perceptual experience is crucial.
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Developmental Timing
• Too much early stimulation is not always good:
• e.g., In vertebrates, vision develops more slowly than
hearing
• Lickliter (1990) suggested that slower vision allows
hearing to develop without competition
• Gave bobwhite quail pre-hatching visual experience
– Cut a window in shell – chicks could see
– Unnatural – normally they only hear
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Developmental Timing
Tested post-hatching on call of quail vs chicken
No early vision – preferred quail call
Early vision – no preference for quail or chicken, but showed
better visual discrimination
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Developmental Timing
Is there a possibility of
sensory over-stimulation?
• What about parents
providing extra stimulation
to infants?
• Is it an advantage or a
disadvantage for
development?
• Question has not been
properly evaluated
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Developmental Timing
• Premature infants may experience deficits due too
much sensory exposure (Als, 1995).
• May lead to enhanced performance in some domains
at the expense of functioning in others.
• Could have an adverse effect on brain development
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Developmental Timing
• Could over-stimulation require
them to process info from the
postnatal environment before
they are “ready”
• Could this have an adverse
effect on brain development?
• Some extra stimulation is
needed to ensure life and health
• These are important and still
controversial issues
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Genotype-Environment Theory
Behavior genetics: studies genetic effects on
behavior and complex psychological characteristics
such as intelligence and personality.
Scarr & McCartney: genes drive experience
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Genotype-Environment Theory
• A child’s inherited characteristics influence which
environments he/she encounters and the type of
experiences he/she has, which in turn influences
his/her development
– “niche picking”
• Parents are also in the loop:
– Their genes influence the type of environment they feel
comfortable in and the genotype of the children
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Genotype-Environment Theory
There are multiple levels of influence.
Genotype of
parent
Genotype of
child
Phenotype of
child
Rearing
environment of
child
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Genotype-Environment Theory
There are three types of genotype-environment effects
that influence development.
Passive effects:
Parents provide genes and environment
Effects can’t be separated
Effects lessen with age
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Genotype-Environment Theory
• Evocative effects:
– Child’s characteristics (e.g., temperament) elicit reactions
from others
– Effects constant with age
• Active effects:
– Child seeks out environments consistent with genotype
– Effect increases with age as child becomes more
independent
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Genotype-Environment Effects
• Parents’ environmental influence on children should
be greatest during early childhood.
– Scarr and Weinberg (1978) found that there was a moderate
correlation between adopted siblings’ IQs.
– The correlation for between adopted siblings’ IQ at
adolescence is 0.
– This finding is likely because passive genotype-environment
effects reflected by the environment provided by parents
decrease with age.
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Genotype-Environment Effects
Active genotype-environment effects increase with
age.
Do genes cause intelligence?
Genes serve to select “appropriate environments”, but
experience is responsible for crafting intellect.
Genetic and environmental effects are dynamic,
having different effects on intelligence at different
points in time.
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Genotype-Environment Effects
As children become more autonomous with age, the
influence of genetic and environmental factors on
individual differences changes.
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Good enough parents?
• Ordinary differences between normal families have
little effect on child development
• Strong influence of gene and environment effects –
parenting has little consequence
• Children around the world become productive
members of society in spite of a wide range of
parenting practices
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Good enough parents?
Children don’t need perfect parents, just “good
enough” parents.
Children who lack the opportunities and experiences
associated with the dominant culture will show
detriments.
Research on “resilient” children shows support for
Scarr’s position.
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Development of the Brain
The human brain provides amazing flexibility and
diversity.
Has the same basic structures as other mammals but
has led to mathematics, physics, art, and language.
Controls all aspects of behavior, from respiration, to
digestion, to learning, and our most advanced forms
of cognition.
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Brain Development
Human adult brain:1400 g; 2% of body weight
Newborn brain: 350 g; 10% of body weight (infants are “top
heavy”)
Adult
Newborn
Infant and adult brains appear similar, but the infant’s is extremely immature
in underlying neurological structure and function.
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Brain Development
The newborn brain is underdeveloped.
Cannot control coordinated movement nor perform
characteristic mental operations.
Our knowledge of brain development and its relation
to cognition has increased thanks to neuroimaging
techniques.
EEG, PET, SPECT, and fMRI (p. 52)
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Neuronal Development
• The nervous system communicates using electrical
and chemical signals transmitted from one neuron to
another.
• The mature brain contains between 10 billion to 100
billion neurons.
• Each is connected to hundreds or thousands of
others at synapses.
– The space between the axon of one neuron and the
dendrites of another. Where chemical messages are
sent/received.
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Neuronal Development
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Transmission from neuron to neuron
• Impulses received by dendrites are conducted to the cell
body where they travel down the axon to the end
terminals
• Neurotransmitters (e.g., serotonin, dopamine,
acetylcholine) are released from synaptic vesicles
• Travel across synaptic cleft (synapse)
• Activate adjacent dendrites
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Transmission from neuron to neuron
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Proliferation, Migration, and Differentiation
Proliferation: cell division by mitosis. Occurs early
in development.
Migration: The cells move to their permanent
position.
Faulty migration may be associated with disorders
(schizophrenia, FAS).
Differentiation: Neurons grow, produce dendrites,
and extend their axons.
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Synaptogenesis and Selective Cell Death
The process of synapse formation.
Rate is greatest in early pre- and post-natal months.
Peak varies for different brain parts.
Pruning begins late in the prenatal period with
selective cell death.
Occurs at different rates for different brain areas.
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Rise and Decline in Neural Development
Brain metabolism follows a similar pattern.
Peaking to a rate that 1.5 times the adult rate at 4
and 5 years of age.
Adult levels are reached at about age 9.
There are also age-related changes in
neurotransmitters.
Increases early in life, followed by subsequent decreases.
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Rise and Decline in Neural Development
This hypermetabolism (around the preschool years)
may be necessary for the rapid learning that occurs
early in life.
Hypermetabolism, large number of synapses, and
increases in neurotransmitters may afford platicity.
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How Do Young Brains Get Hooked Up?
Previously, it was thought that genes dictate the
formation, migration, and differentiation of neurons,
and experience “fine-tuned” the brain.
Now there is a greater emphasis on postnatal
experience.
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How Do Young Brains Get Hooked Up?
• Greenough (1980s): Brain development is an
extended process strongly influenced by postnatal
experience
• Specific experiences produce neural activity that in
turn determine which of the excess synapses will
survive
– Nervous system prepared by evolution to expect certain
types of stimulation (e.g., patterned light, moving objects)
– These experiences form and maintain synapses
• Experience-expectant processes
– Certain functions (e.g., visual acuity) will develop for those
who have the experience – if not, the connections are
pruned
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How Do Young Brains Get Hooked Up?
Maurer et al. studied infants who were born with
cataracts and had them removed at different points in
life.
Those who had the cataracts removed within the first
several months after birth displayed the typical
pattern of visual development.
Those who had the cataract removed later showed
poor visual development, and poor face processing.
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Selectionist Theories
Neural level – neurons, dendrites, synapses
are overproduced in early development
Those that are used survive, those that are not are lost
(pruning)
“Use it or lose it”
Pruning is important to later development
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Greenough also proposed …
• Experience-dependent processes
– Neural connections that reflect unique
experiences
• These experiences result in the alteration of neural
connections.
• So impoverished environments result in “pruning”
through disuse
• What determines the survival of synaptic connections
is the principle of use.
– Those activated by sensory and motor
experiences survive, the remainder are lost.
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The Neocortex
A multilayered sheet of neurons measuring 3-4 mm.
The part of the brain primarily associated with
thinking.
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The Neocortex
Consists of two halves joined
by the corpus callosum.
Primary Areas receive info
directly from the senses.
Or, they send instructions to
body to muscles.
Secondary areas integrate
information and connect with
other brain regions.
Responsible for complex
thought.
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The Neocortex
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The Neocortex
The prefrontal lobes appear important for inhibition.
A not B task
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The Neocortex
Diamond (1991) showed that children are
increasingly able to inhibit their responses.
May be related to development of the prefrontal cortex.
There are also changes in brain structure and
function that occur later in life.
Adolescents often display self-centeredness,
emotional instability, increases in risk-taking, and
seeking of novelty.
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The Neocortex
This time period is associated with changes in the
frontal lobes (decrease in relative size, change in
organization).
There are also changes in the distribution of
neurotransmitters in the frontal cortex and the limbic
system.
These changes may be adaptive to force adolescents
to become independent from their parents.
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The Brain’s Plasticity
• Refers to the potential outcomes that are possible
for a single neuron, bundles of neurons, or larger
brain structure
• Capacity for change in structure or function
• Infant brain is only weakly specialized
• Use or disuse of neural circuitry determines
plasticity
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Neuronal Plasticity
There is no plasticity on neuronal production.
There is plasticity in synapses as connections form
throughout life.
The formation of new synapses is based on experience.
Evidence comes from enrichment experiments.
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Neuronal Plasticity
• Rats are raised in enriched or impoverished
environments
– Group rearing, platforms, objects vs. single
rearing, bland environment
• Enriched rats superior to deprived rats
– Problem solving
– Maze learning
– Heavier cortex – larger neurons, more dendrites
– 20% more synaptic connections
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The Brain’s Plasticity
Plasticity greater in infancy – brain not “set” -synaptic connections “up for grabs” over extended
period of growth.
With some exceptions, recovery from brain injury
more likely in children than adults.
Brain damage to language areas.
But the human brain is not entirely plastic, even in
children.
The effects can be reversed in brain areas that
control general functioning.
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The Brain’s Plasticity
The plasticity of behavior and intelligence is attributed
to the slow growth of the brain.
This means the brain is inefficient when we are
young.
The plasticity afforded allows us to overcome early
deprivation.