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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.