Developmental Psychology: Issues and Methods
StaChangeversus DPsychologyal Sensitive
Nature and Nurture: To what extent is our development the product of heredity
(nature) or product of the environment (nurture)? How do nature and nurture
Critical and Sensitive Periods:
Critical Period: An age range in which certain experiences MUST occur for
development to proceed normally or along a certain path.
Sensitive Period: An optimal age range for certain experiences, but if those
experiences occur at another time, normal development will still be possible.
Continuity Vs. Discontinuity: Is development continuous and gradual? Or is it
discontinuous, processing through qualitatively distinct stages?
Stability Vs. Change: Do our characteristics remain consistent as we age?
There are five developmental functions that developmental psychologists use to
address the above issues. • An ability present at or before birth that remains relatively
No Change constant across the lifespan.
• An ability not present, or very immature, at birth that develops
Continuous gradually over months or years and then remains contstant over
• An ability that progresses in stages, with relatively rapid shifts
Stages from a lower level of performance to a higher level.
• An ability that emerges after birth, peaks, and disappears with
• An ability that is present early in life, disappears temporarily,
U-Shaped and re-emerges later.
Cross-Sectional Design Compare people of different ages at the
same point in time. Test each person
only once and compare how well the
different age groups perform.
Benefit: Data from many age groups can
be gathered quickly
Drawback: Different cohorts grew up in
Longitudinal Design Repeatedly tests the same cohort, as it
Drawback: Very time consuming and
over time the sample size may shrink.
Sequential Design Combines a cross-sectional design and a
longitudinal design. Repeatedly test
several age cohorts as they grow older
and determine whether they follow
similar development patterns. Prenatal Development
•Week 9 - Birth
•Week 3 - Week 8 •Week 24: Eyes
•Embryo •Age of Viability
Stage •Umbilical Cord
•Heart Begins to
•First 2 weeks Beat
Approximately the first two weeks of growth and development.
Zygote: The fertilized egg.
Zygote undergoes repeated cell division.
Week 3 – Week 8.
The cell mass is now called an embryo.
Placenta and umbilical cord develop.
o Placenta: Located on the uterine wall, the placenta contains
membranes that allow nutrients to pass from the mother’s blood to
the umbilical cord.
o Umbilical Cord: The umbilical cord contains blood vessels that carry
these nutrients and oxygen to the embryo and waste products back
from the embryo to the mother. (Develops in the 5 week).
The heart begins to beat by the end of the eighth week.
Endoderm differentiates into the digestive system.
Mesoderm differentiates into skeleton, muscles, reproductive and circulatory
Ectoderm differentiates into nervous system and skin.
The embryo is now called a fetus.
During this stage, muscles become stronger and bodily systems continue to
14 Week – Fetal movements are felt. 18 week – Fetal heartbeat can be detected.
By week 24, the eyes begin to open.
By week 28, the fetus attains the age of viability – it is likely to survive
outside the womb in case of premature birth.
Critical Periods in Prenatal Development: The most important critical period is the
first 8 weeks after conception because after that time the risk for major defects in
the following structures drops of considerably: heart, arms, and legs.
Genetics and Sex Determination
The Y chromosome contains a specific gene known as the TDF Gene; that
triggers male sexual development.
At 6-8 weeks after conception, the TDF initiates the development of the
Once formed, the testes secrete sex hormones called androgens that continue
to direct a male pattern of organ development.
Teratogens: Substances that can cause birth defects in babies.
Antibiotics: Can cause deafness, or bone and tooth deformities.
o Tricyclic’s have been associated with some birth defects, no effect on
o Lithium has been associated with cardiovascular abnormalities.
o Prozac – no adverse side affects found.
Cigarettes Higher risk of infant illness.
Low birth weight.
Later, children are more
hyperactive, lower IQ, impaired
Marijuana Later difficulties (tremors and
Later, children are more
hyperactive, lower IQ, impaired
Caffeine Complications during labor and
delivery Drinking During Pregnancy
Regular Drinking (1-2 Daily) Causes impaired fine motor skills and
slower information processing.
Irregular Binge Drinking (5 or More) Lower intelligence and academic and
Alcohol Abuse (6 or More Daily) Fetal Alcohol Syndrome
Fetal Alcohol Syndrome is a group of severe abnormalities that results from
prenatal exposure to alcohol.
Infancy and Childhood
The Amazing Newborn
In a study performed by Fants, a preferential looking procedure was used to study
infants’ visual preferences.
Infants preferred complex patterns, rather than simple patterns.
A newborn is born with innate reflexes:
Tonic neck reflex
Whereas vision is poor, an infant’s sense of smell and sense of hearing are both
A new visual preference can be establish in newborns by using the visual
habituation procedure – the same stimulus is presented repeatedly until infant
looking time declines.
An auditory habituation procedure was used to study infant memory.
Preferential Looking Procedure Used to study infants visual preferences.
Visual Habituation Procedure The same stimulus is presented
repeatedly until infant looking time
Auditory Habituation Procedure Used to study infant memory. Sensory-Perceptual Development
Physical, Brain, and Motor Development
Maturation: The genetically programmed biological process that governs our
growth, our bodies and movement (motor) skills develop rapidly during infancy and
Cephalocaudal Principle This principle reflects the tendency for
development to proceed in a head-to-
Proximodistal Principle This principle states that development
begins along the innermost parts of the
body and continues toward the
outermost parts of the body.
The brain shows most rapid growth by 6 months of age, where it has doubled in
weight. By 5 years of age, the brain has reached 90% of its adult weight.
Integrated Model of Development
Genetics/Biology sets limits.
Experience contributes to development.
Reflexes: Automatic, inborn behaviors that are elicited by specific stimuli.
Three Points that Apply Across The Realm of Human Development
Biology Sets Limits on Environmental The best nutrition will not enable most
Influences people to grow taller, and no infant can
poo before the nerve fibers that help to
regulate bladder control have matured.
Environmental Influences Can Be Nurturing environments foster physical,
Powerful sensory-motor, and psychological
growth, while impoverished
environments can stunt growth.
Biological and Environmental Factors Enriched environments enhance brain
Interact development. In turn, brain development
facilitates our ability to learn and benefit
from environmental experiences. Cognitive Development
Piaget’s Stage Model
Building mental representationsof the world through direct interaction with it.