intro to child psych

nature-nurture

• nature: biological endowment, especially genes received from parents

• nurture: physical and social environments that influence our development

• they work TOGETHER to shape development

continuous-discontinuous

• continuous: changes with age occur gradually in small increments; development occurs skill by skill, task by task: quantitative; learning theorists; Watson & Bandura

• discontinuous: changes with age include occasional, large shifts; developmental shifts result in qualitative changes; stage theorists; piaget, freud, erikson, kohlberg

learning theories

emphasizes role of experience, rewards and punishment

• nurture + continuous

behaviorism (john watson, b.f. skinner)

• a learning theory

• reinforcement: increases future likelihood of behavior

• punishment: decreases future likelihood of behavior

social learning theory (albert bandura)

• a learning theory

• reinforcement and punishment are powerful, but people learn by watching others (imitation, observational learning)

• imitation is not just mimicry

cognitive development theories

• focus on mind: thought processes, construction of knowledge

• how children think and how thinking changes over time

• roots in nativism (Rousseau)

• modern cognitive development theories: more interactionist

• major figures: Piaget, Vygotsky

• nature + discontinuous

piaget’s thinking

• children are like scientists, they want to understand the world and how it works

• children revise their theories radically at a few critical points, leading to new theories

• revisions happen in a universal sequence at particular ages

evolutionary theories

applies concepts of natural selection and adaptation to human behavior

• charles darwin

• focus on functions of behaviors: how did behavior ensure survival of the species?

• examine patterns of behavior across human societies and cultures

• e.g. Kindchenschema (baby schema0l attachment

• some propose “critical periods”

• nature + discontinuous

ecological theories

• stresses effects of context on development

• and child’s active role in selecting and influencing the contexts

• and child’s personal characteristics

• most prominent: bronfenbrenner

• nurture and unspecified between dis/continuous

hypotheses

• educated guesses that need to be tested

• hypotheses not supported by evidence are rejected

the scientific method steps

1. choose a question to be answered

2. formulate a hypothesis

3. develop a method for testing the hypothesis

4. use data acquired to draw a conclusion regarding hypothesis

interviews

• structured interviews:

  • asking identical questions of may children for quick and straightforward answers

• clinical interviews:

  • begin with prepped questions, but follow child’s lead for in-depth info about an individual child

observations

casually observe subjects and record how they behave in their usual environments

• naturalistic observation: observe people as they behave in real-life situations

  • can yield detailed info about children’s everyday lives, behaviors

  • but behaviors may occur only rarely in everyday interactions, observer bias and influence, hard to know which factors are influential

• structured observation

  • researcher creates setting (typically in lab) that is likely to bring out behavior of interest, observes behavior and relates it to other factors

  • structured setting may distort behavior, observer bias and influence

research designs

cross sectional, longitudinal, and microgenetic

reliability & validity

• reliability: extent to which a measure provides a consistent index of a characteristic

• validity: whether the measure truly measures what researchers think it measures

correlational studies

look at relations between variables as they exist naturally in the world

• measure two variables for each person

• see whether the two variables are related

example:

• person’s intelligence and number of friends

• two aspects of relations to measure:

  • whether the relation between two variables is positive, negative, or no correlation

  • the strength of the relation

• does not address cause and effect, third-variable problem, but helps determine whether variables are related

experimental studies

a systematic way of manipulating the key factor(s) that the investigator thinks CAUSE a particular behavior

experimental designs

if children exposed to one experience and children exposed to a different or no experience subsequently behave differently, then those subsequent differences in behavior resulted from the differences in experience

• if children exposed to one experience —> experimental group

• children exposed to different or no experience —> control group —> independent variable

• dependent variable

• causal conclusion

two critical aspects of experimental design

• random assignment: each child has an equal chance of being assigned to any of the groups → so groups are comparable at outset

• experimental control: all children are treated identically except for the one factor (experience) that researcher is interested in

prenatal development

prenatal period: from conception (single cell) to birth (newborn baby); most rapid phase of development

• past view: genetically-determined growth

• current view: interactive process, environmental factors play a role

stages of prenatal development

average of 38 weeks; germinal, embyronic, fetal

germinal period

• first 2 weeks after conception

• conception: fusion of sperm and egg to form one fertilized egg (zygote)

• sperm and egg each contain only 23 chromosomes → at conception, they form a single cell containing 23 pairs of chromosomes

• zygote: fertilized egg. zygote divides and grows through mitosis. inner cell mass

embryonic period

3rd to 8th week

• ball of cells differentiates

• inner cell mass → embryo

  • all major organs begin to form

• rest of cell → support system

  • amniotic sac, amniotic fluid

  • placenta

  • umbilical cord

• brain development begins

fetal period

9th week to birth

• continued growth and differentiation

• all internal organs present but must develop further

• by 28th week, fetus could survive outside womb (brain and lungs sufficiently developed)

• newborn baby born after ~38 weeks

developmental process

1. mitosis: cell division

2. cell differentiation:

   • initially all cells are interchangeable, flexible → embryonic stem cells

   • then begin to specialize, become inflexible

3. cell death (apoptosis)

4. cephalocaudal growth

fetal experience and learning

• uterus and amniotic fluid buffer fetus from too much stimulation

• but fetus does experience sensory stimulation

• touch:

  • first sense to develop (by 8 weeks)

  • fetus comes into contact with umbilical, parts of its own body

  • even shows some “intentional” touching (e.g., of twin vs. self or uterine wall)

• taste:

  • amniotic fluid contains many flavors, fetus can detect the flavors, has a sweet tooth

  • learning:

    • newborns prefer tastes they experienced in womb, fetus becomes familiar with flavors in breastmilk, may contribute to cultural food preferences

• smell:

  • amniotic fluid takes on odors of what mother has eaten

  • learning:

    • newborns prefer odor of their own amniotic fluid

• hearing:

  • fetus hears mother’s heartbeat, blood flow, voice, etc.

  • recognize sound of their own mother’s voice, rhythm and pitch but not specific context and words

  • learning:

    • newborns remember sounds heard in womb → prefer to listen to own mother’s voice, prefer language and music they heard in womb

• vision:

  • least likely to be stimulated prenatally; detect general changes in illumination, can open eyes and practice blinking, fetus will have visual preferences by third trimester

teratogens

an external agent that can cause damage or death during prenatal development

• adverse effects: spontaneous abortion, structural abnormalities, growth retardation, impaired mental development

• some effects apparent at birth, others emerge over development

• duration and timing of exposure is critical (sensitive periods)

• organ systems are more vulnerable when their basic structures are being formed

alcohol

• most common human teratogen, leading cause of fetal brain injury

• alcohol crosses placenta into fetus’ blood stream

• fetus cannot metabolize alcohol quickly; stays in fetus’ system longer

• interferes with delivery of oxygen and nutrition to fetus’ tissues, organs, brain

• can lead to fetal alcohol syndrome

cigarettes

• less oxygen for fetus

• leads to slow fetal growth and low birth weight

• higher risk of sudden infant death syndrome (SIDS)

SIDS (sudden infant death syndrome)

• interaction between underlying biological issue + environmental stressor (limited oxygen)

• several steps to reduce risk:

  • putting infants to sleep on their back

  • caregivers should not smoke

  • firm mattress, fitted sheets, no pillows

  • no big blankets

  • breastfeeding

chromosomes

threadlike structures that contain genetic material

• egg and sperm each contain 23

• at conception: combine to produce 23 pairs

• chromosomes made of two twisted strands of DNA → carries your genetic code, hereditary information

genes

• segments of DNA

• provide biochemical instructions for formation and functioning of an organism

• basis for all human characteristics and abilities

• genes - functional units of heredity

genotype

complete set of genes that makes up a person’s heredity

phenotype

observable expression of genotype → physical, behavioral, and psychological features resulting from interaction of genes and environment

gene expression and regulation

genes have to be “switched on” in order to influence development and behavior → by regulator genes

• e.g., during embryo development

• role of environment

dominance patterns

• many genes have two or more different forms: alleles

• alleles of a given gene contribute to different developmental outcomes

• some genes have two alleles: dominant and recessive → a person could inherit two of the same allele or one of each allele (homozygous vs. heterozygous)

  • homozygous: corresponding trait is expressed

  • heterozygous: dominant allele is expressed

behavior genetics

• dominant-recessive pattern is relatively infrequent, does not pertain to complex phenotypes

• phenotypes that behavioral scientists are interested in: polygenic - many different genes contribute to these

• behavior genetics: to the extent that genetic factors are important for a trait/behavior, individuals who are more genotypically similar will be more phenotypically similar

• twins (monozygotic vs. dizygotic), adoption studies, and adoptive twin studies

three principles of heredity-environment interactions

• heredity and environment interact dynamically throughout development (effects of abusive parenting depend on genotype)

• genes influence the kind of environment to which a person is exposed and the person seeks out → outgoing vs. shy child → niche picking

• environment can alter the functioning of genes and gene expression (epigenetics)

epigenetics

study of how environment contributes to stable changes in gene expression

• functions through methylation: a process that reduces expression of certain genes (“silences” gene expression)

• e.g., stress responses in rats (cross-fostering studies → a pup that is raised by an anxious, low-nurturing mother becomes an anxious adult, vice versa)

• similar effects in humans

neurodevelopment

read about basic brain structures (neuron and cortex) in textbook

prenatal brain development

neurogenesis

creation of neurons through cell division

• begins ~42 days after conception, nearly complete mid-way through gestation, though adults continue to generate new neurons throughout life

• after they are generated, neurons migrate: move outwards from center

• at destination, they specialize in structure and function

synaptogenesis

creation of synapses with other neurons

• each neuron forms synapses (connections) with thousands of others = trillions of synapses

• rapid before birth, continues after birth

• timing and rate vary by cortical areas

synaptic pruning

selective elimination of synapses

• synaptogenesis results in far too many synapses

• trimmed down through synaptic pruning

• synapses that are weak (rarely activated) are eliminated (“use it or lose it” principle)

• begins at birth, continues in waves through childhood into early adulthood

• timing and rate vary by cortical areas

postnatal brain development

brain size: 25% at birth, 90% by age 5

plasticity

capacity of the brain to be affected by experience

• two kinds of plasticity:

  • experience-expectant

  • experience-dependent

experience-expectant plasticity

• brain is wired to develop “normally” given certain general experiences that have been present in our evolution

• e.g., voices and other sounds, movement, patterned visual stimulation

• brain can “expect” certain input for structuring and development (based on our evolutionary history)

experience-dependent plasticity

• brain is also shaped by idiosyncratic experiences

• e.g., musical training

sensitive periods

times when brain is especially sensitive to particular environmental stimuli

• particular environmental input is especially important or influential for brain development and reorganization

• window gradually closes

• particularly relevant for experience-expectant development (e.g., language learning)

most common methods for measuring brain development

• MRI (functional, structural)

• EEG (functional)

• MEG (functional)

• fNIRS (functional)

• ultrasound (structural, newly functional)

• spatial resolution: where in the brain?

• temporal resolution: when in the brain?

the human brain

frontal lobe, parietal lobe, occipital lobe, temporal lobe

frontal lobe

• planning, decision-making, impulse control, voluntary movement, attention, memory, personality, language production, social cognition, etc.

how does the brain develop?

back (occipital) to front (frontal) → minimally complex (automatic) to most complex (slow and deliberate)

• social perception develops very early across the brain

medial prefrontal cortex (mPFC)

mPFC responses to social smiles at 11 months → individual differences in sociability at 18 months

superior temporal cortex (STC)

STC responses to moving faces at 7 months → individual differences in sociability at 18 months

connectivity in the developing brain

brain regions that work together for common functions tend to have similar brain activity patterns (functional connectivity) and more white-matter tracts (structural connectivity)

• default mode network

• fronto-parietal network

• sensorimotor network

• visual network

infants with increased functional connectivity between two “social brain” regions (mPFC & STS) → more smiling and laughing during social interactions with caregivers

the role of experience in brain development

• infants with history of caregiver maltreatment show perceptual biases for angry faces

• infants with history of mothers with greater sensitive care have greater neural responses to happy faces in the prefrontal cortex

• prenatal social disadvantage during pregnancy → excessive maternal immune activation → global decreases in brain volume and gyrification in infants starting in utero

brain development and genes (epigenetics)

• infants with higher OXTRm (less oxytocin) show greater responses to anger and fear and attenuated responses to happiness in IFC

• OXTRm as an epigenetic marker contributing to early brain function

brain, behavior, and genes

genetic variability in the oxytocin system (CD38) impacts infants’ brain (frontal assymetry) and behavioral (eye-tracking) social development

sensation

processing of basic information from the external world by the sensory receptors in the sense organs (eyes, ears, nose, etc.)

perception

processing of organizing and interpreting sensory information

habituation/dishabituation

• respond with less attention (“boredom”) to stimuli that one has experienced repeatedly

• dishabituation to new stimulus indicates infant has noticed that new stimulus is different from old

visual acuity

infants’ visual system is immature

• cones: responsible for visual acuity: how clearly one can see fine details

• infants have low visual acuity

• prefer to look at: patterns than solid gray surfaces, high contrast patterns than low contrast patterns

• but develops rapidly, close to adult acuity by 8 months, full adult acuity by 6 years

color perception

cones are also responsible for color vision, infants have poor color vision

• but develops rapidly: 2-3 months → similar to adults

face perception

infants are drawn to faces from birth

• newborns: general preference for top-heavy images

• over the next 2-3 months:

  • recognize and prefer own caregiver’s face

  • prefer human faces

  • distinguish between different human faces

object perception

• object segregation

• important cue: common movement

  • 2-4 months olds

  • not newborns

over development, use general knowledge, experience, and other cues (color, shape, texture)

depth perception

• binocular disparity: retinal images of an object are not identical in both eyes (due to distance between eyes) → the closer the object, the greater the disparity between the two images

• stereopsis: brain combines the differing neural signals, leading to perception of depth

• emerges around 4 months

audition

• auditory system is fairly well developed

• but ears and auditory pathways in brain must still mature

• other auditory improvements:

  • auditory localization → newborns are not great at localizing sounds, improves over the first few years

intermodal perception

• integration of information from two or more sensory modalities

• emerges in first few months

  • oral-visual, manual-visual, auditory-visual

contributors to development

nature-nurture interaction

• 2 examples: sensory deprivation and perceptual narrowing (other race effect and language perception)