Psychology of Infancy
Defining development,
prenatal development,
brain development
D. Messinger, Ph.D.
Questions (single essay format)
Define development. Argue for why you believe development does or
does not have an endpoint.
Describe genetic and experiential factors in brain development
referring to experience expectant and experience dependent factors.
Give examples of how prenatal sensory experience impacts sensory
Describe similarities between the brain development of the postnatal
child and differences in the brains of adult humans and macaque
Is it is all over after age 3?
What are some basic patterns of synaptic and brain development in
How they are influenced by experience?
What can go wrong in this pattern?
Provide examples from Nelson.
What is the take-home message of Thursday's reading, The Seductive
Allure of Behavioral Epigenetics?
Development defined
Development defined
Individual change that is, normative, nonreversible, relatively stable, and sequential.
Normative process
Everyone’s doing it
Reorganization of the entire person
Relatively stable
You can’t go back,
Sequential change
Crawl before you walk
Is development
Increasing functionality in all things?
Loss of perceptual acuity in non-native
languages between 6 & 12 months
Is development
Headed toward a goal?
Development has normative outcomes,
but time goes forward
prior events cause subsequent events
not the opposite
What does Thompson (2001, p. 21) mean?
“A drive to development is inborn, propelling
the human infant toward learning and mastery.”
Three models
In class assignment:
What would a cross-tab of the
transactional model look like?
What does individual
development look like?
Prenatal brain development
Overview of brain growth
Subcortical areas responsible for reflexes
develop first
E.g. spinal cord
Followed by cortical areas in a specific
What is most human develops last
Most but not all neurons present at birth
Synapses develop
Myelin develops
Cortical Expansion
Similar patterns of cortical expansion
between infants and adults as
between macaque monkeys and adults
“The pattern of human evolutionary
expansion is remarkably similar to the
pattern of human postnatal
(Hill et al., 2010)
Postnatal cortical surface expansion.
Hill J et al. PNAS 2010;107:13135-13140
©2010 by National Academy of Sciences
Fig. 1. Postnatal cortical surface expansion. Maps of postnatal cortical surface expansion
on the standard mesh average inflated term infant surfaces for both hemispheres,
shown in lateral (A), medial (B), dorsal (C), and ventral (D) views. The absolute expansion
scale indicates how many times larger the surface area of a given region is in adulthood
relative to that region’s area at term. The relative expansion scale indicates the
difference in proportion of total surface area at term birth and adulthood.
Comparison of evolutionary and
postnatal cortical surface expansion.
(A) Map of regional
evolutionary cortical
expansion between an
adult macaque
and the average human
adult PALS-B12 atlas
(right hemisphere only).
Evolution expansion
scale indicates how
many times larger the
surface area is
in humans relative to
the corresponding area
in the macaque. (B) Map
of human postnatal
cortical expansion
(combined left and
right hemispheres)
for comparison
(detailed in Fig. 1
legend). (C) Correlation
map comparing
postnatal to
evolutionary cortical
surface expansion.
Different regions,
different rates
Regions responsible for lower cognitive
functioning develop more rapidly
Regions responsible for higher cognitive
functioning develop more slowly
They may have selection pressure to remain
To facilitate the development of regions more
crucial for early surival
To limit overall brain size at birth by focusing
on areas most necessary for early survival and
keeping the head small (birth canal)
Writing assignment
What processes do Tierney and
Nelson discuss under the concept of
Early Stages of Brain Development?
Define three of these process.
differentiation of
areas of cortex
Infant is born
during height of
brain development
Tertiary sulci
develop from 1
month before to 12
months after birth
Four levels of brain development
From Nelson, 1999
Creation of a tube
Synapses are connections
between neurons
Neural migration
Many elements of initial neural migration
specified genetically
By 20 weeks gestation, 100 billion neurons!
 50,000 – 500,000 neurons per minute
Neurons follow path of glial cells outward
from ventricles
To form 6 layers of cortex
Proliferation & migration of neurons
General pattern of brain development
genetically specified
By 20 weeks, most neurons present
3rd - 16th prenatal week most crucial
At 8 weeks, head is half of fetus
But specific connections depend on generic
growth processes and sensory-motor
Trillions of connections still forming
Trimming of these connections is developmental
Neural development:
Once in place, synapses are overproduced
somewhat haphazardly
1 year old has 150% more synapses than adult
These are pruned (diminish) during
Repetition of sensory-motor patterns
create more specific set of experience
dependent synaptic linkages
Time lapse sequences of radial
migration (also known as glial
guidance) and somal translocation
Neuron migration
Typical and Atypical
Increase in complexity of neural
Like a
How do the correct synapses
15,000 synapses for every cortical neuron
1.8 million per second in first 2 years!
Cerebral cortex triples in thickness in 1st year
Sensory and motor neurons must extend to
correct brain are and form correct
This quantity of information cannot be
genetically micro-managed
Two types of experience in brain
“How common early experiences provide
essential catalysts for normal brain
Early visual stimulation, hearing, exposure to
language, coordinating vision and movement,
“The developing brain “expects” and
requires these typical human experiences,
and relies on them as a component of its
“How individual experience fosters new brain
growth and refines existing brain structures”
“Can be unique to an individual”
Singing, music
Neural Darwinism (Edelman)
Use it or lose it
What is not used, is pruned
What is used, develops stronger connections
Organism & environment are system that
shapes brain
Brain development is guided by environment
Brain enables behavior which shapes brain
Synaptic development is not teleological
The fetus as constructing its
own development
Fetal behavior impacts physical
In chicks prevented from moving,
cartilage turns to bone
Fetal sensory experience impacts
sensory development
Mice whose tongues were anesthetized
had malformed cleft palates
Prenatal sensory experience
impacts sensory development
Hearing typically develops before sight
Rats, ducklings, and quail chicks exposed to
visual stimulation prenatally
before they normally would
lose hearing ability at birth
Normal sensory development contingent on
extra-fetal environment
Differences in the timing of augmented prenatal stimulation
led to different patterns of subsequent auditory and visual
responsiveness following hatching.
When augmented tactile and vestibular stimulation coincided
with the onset of auditory function (Days 9-14), embryos
subsequently failed to learn a species-typical maternal call
prior to hatching.
No effect on normal visual responsiveness to species-typical maternal
cues when exposure to tactile and vestibular stimulation coincided with
the emergence of visual function (Days 14-19)
When exposure took place after the onset of visual functioning (Days
17-22), chicks displayed enhanced responsiveness to the same maternal
visual cues.
Honeycutt, H. & R. Lickliter (2003). Developmental Psychobiology 43: 71-81. The influence of prenatal tactile and vestibular stimulation
and visual responsiveness in bobwhite quail: A matter of timing
“Promoting early brain
Re-discovery of importance of early
“How brain connections grow and change as
a result of stimuli from the environment.
How early stress can be harmful to the
developing brain.
Principle of "use it or lose it"
Seven ways to support brain development:
“Considerable misunderstanding
of early brain development
occurs when neurons and
synapses are considered
independently of the
development of thinking, feeling,
and relating to others.”
Thompson, 2001, p. 29
Is it all over after 3?
Is the course of development set in
Early experience is important
But, with some exceptions, human beings
remain open to the positive effects of
additional experience
The same is true for the impact of experience
on brain development
How important is it to ‘stimulate your child’s brain’?
Implications for Policy and Programs
Sensitive periods & Neuroplasticity
Financial payback
Early identification
and intervention
Abecedarian Intervention Project
Children who participated in the early intervention program had
higher cognitive test scores from the toddler years to age 21.
Academic achievement in reading and math was higher from the
primary grades through young adulthood.
Intervention children completed more years of education
more likely to attend a four-year college.
Intervention children were older when their first child was born.
Mothers whose children participated in the program achieved
higher educational and employment status than mothers whose
children were not in the program.
Results especially pronounced for teen mothers.
Enhanced language development appears to have been
instrumental in raising cognitive test scores.
Implications for practice
It is important to provide a safe, warm,
supportive, stimulating environment for
But its never too late to improve
developmental outcome for an individual
At any point, current conditions are as
important as past conditions
Baby media
No flashcards…
Brain Overgrowth in the First
Year of Life in Autism
The clinical onset of autism appears to
be preceded by 2 phases of brain
growth abnormality: a reduced head
size at birth and a sudden and
excessive increase in head size between
1 to 2 months and 6 to 14 months.
Abnormally accelerated rate of growth
may serve as an early warning signal of
risk for autism
Courchesne, Carper, Akshoomoff, (2003)
Why overgrowth?
Rate of head circumference growth as a function
of autism diagnosis and history of autistic
Webb, Sara Jane; Nalty,
Theresa; Munson, Jeff;
Brock, Catherine; Abbott,
Robert; Dawson, Geraldine
Journal of Child Neurology,
Vol 22(10), Oct 2007, 11821190. doi:
Birth Process
Midwifery – the first profession
Prenatal to Postnatal
Preparation for Birth
-Braxton Hicks contractions
-Hormonal activities (e.g. progesterone -> estrogen =
muscle activity)
Stages of Birth
From womb to birth canal. Longest stage, uterine
contractions (enables mother’s cervix to expand).
From birth canal to outside. Pushing.
Afterbirth. Delivery of the placenta
Survival after Birth
-Baby breathes on its own.
-Change of blood circulation (oxygenation now occurs
from the lungs not the placenta
Human birth – cephalo-pelvic
Are human beings evolving?
How might the rise in the rate of delivery by
c-section be related to evolution?
Final project ideas
Prenatal maternal stress
Prenatal infection
Prenatal behavior
Impact on outcomes (after birth)
Human birth – a social process
"In nonhuman primates, the fetus usually emerges with its
face toward that of its mother. She may then reach down
and pull it up toward her along the normal flexion of its
"In humans, however … the close equivalence of
cephalopelvic dimensions has resulted in … infant being
born facing away from its mother.
In this position, the use of her own hands to assist delivery
before the shoulders have emerged could result in pulling
the infant against the normal flexion of its body, again with
the risk of injury particularly to the nerves of the neck."
Wenda R. Trevathan, Human Birth, (New York: Aldine de
Gruyter, 1987), p. 89-92
Human birth – graphic content
More medical, ‘produced’ video
Just video of birth
NPR segment on birth process
Prenatal development is usually
divided into three main periods.
Zygote -
covers the first two weeks after conception
ends when the zygote implants into the wall of
the mother's uterus.
Embryo from two to eight weeks following conception
the major organs and bodily systems form
from eight weeks after conception until birth
grows tremendously in size and weight.
Zygotic cell differentiation
From zygote to embryo
The question
The zygote grows through cell
Mitosis - One for one copying of all 23
All cells contain the same genetic
information in their nuclei
But qualitatively different types of
cells develop in different parts of the
How does this occur?
General processes yield specific
Cells clump together as a sphere
This changes the extra-cellular
environment of cells on the inside and
outside of the sphere
Differences in environment impact
cell’s genetic make-up to activate
different proteins
Genes in Environment
Environmental factors influence
development from the start
Cells are environments
The uterus is an environment
The fetus participates in actively
constructing its own development
it is not passively constructed
What do you think?
Stem cell debate
Assistive reproduction technology
Additional readings
Plomin, et al. The genetic basis of complex human behaviors.
Plomin, R., & Rutter, M. (1998). Child development, molecular
genetics, and what to do with genes once they are found.
Child Development, 69(4), 1223-1242.
Rutter. M. (in press [2002]. Nature, nurture, and
development: From evangelism through science towards
policy and practice. Child Development.
Collins, W. A., Maccoby, E. E., Steinberg, L., Hetherington, E.
M., & Bornstein, M. H. (2000). Contemporary research on
parenting: The case for nature and nurture. American
Psychologist, 55(2), 218-232.
Sleigh, M. J., Columbus, R. F., & Lickliter, R. (1998).
Intersensory experience and early perceptual development:
Postnatal experience with multimodal maternal cues affects
intersensory responsiveness in Bobwhite Quail Chicks.
Developmental Psychology,Messinger
34(2), 215-223.