fall, 2005 1 human development 1 psychology 3050: biological bases of cognitive developement dr....

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HUMAN DEVELOPMENT 1PSYCHOLOGY 3050:

Biological Bases of Cognitive Developement

Dr. Jamie DroverSN-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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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 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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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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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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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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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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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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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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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 self-

organization through bidirectional interactions of the elements at various levels.

Implies plasticity in development

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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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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 bottle-fed.

The benefits of breastfeeding for IQ are influenced by combination of alleles that influence how fatty acids are processed.

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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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• 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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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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• 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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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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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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• 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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• 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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• 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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There are multiple levels of influence.

Genotype ofparent

Genotype ofchild

Phenotype ofchild

Rearing environment of child

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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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• 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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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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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

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Human adult brain:1400 g; 2% of body weight

Newborn brain: 350 g; 10% of body weight (infants are “top heavy”)

Infant and adult brains appear similar, but the infant’s is extremely immaturein underlying neurological structure and function.

Newborn

Adult

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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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• 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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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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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

Selectionist Theories

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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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• 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

Neuronal Plasticity

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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.

fall, 2005 1 human development 1 psychology 3050: biological bases of cognitive developement dr....

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