Lecture 1 - Introduction
What, when, why and how do we develop. What is developmental psychology?
● Sequential: based on several stages/levels/phases.
● Unidirectional: earlier changes are prerequisite for later ones. You always aim for higher,
you can only go in one direction.
● End state: higher value than the original state.
● Irreversible: Once you reach a higher level, you can’t go back.
● Qualitative: structural transformations.
● Biological growth: independent of cultures. This is seen as the basis.
● Universal: the same for al humans.
Extended conception of development:
● Is not necessarily based on stages
● Doesn’t always have end states, which are of higher value (e.g. personality)
● Isn’t always irreversible.
● Are both qualitative and quantitative.
● Can be universal but also interindividual.
● Are affected by culture and biology
● Can be intraindividual modifiable and constrained. We are plastic.
Developmental psychology deals with differences within persons across the lifespan, and
differences and similarities amongst persons. The aim is to describe intraindividual changes and
interindividual changes. What develops when how, where and why?
What: psychology (cognition, emotions, behavior), biology (brain, neurophysiology) and social
(family, friends). Developmental psychology focuses on normative development (behavior and skil s in al
individuals) and individual differences. Individual differences can happen within a range of
normative development, or they can fal outside the range. When: biological age is never responsible for changes. Changes are correlated with changes.
Age is the ’vehicle’ that carries the change. We want to link change to ‘why’, not ‘when’.
● Variability = short-term fluctuations that can be reversed.
● Change = more or less enduring, long-lasting. Reversal (nearly) impossible.
Variability can predict change.
We can treat age in a continuous way, or you can compare specific age groups (bv
volwassenen en adolescenten).
We can investigate individuals of different ages at one point in time. This is a cross-sectional
design. In this way you can measure interindividual differences. However, we can also
investigate the same individuals across different points in life. This is a longitudinal design.
Here we can measure intraindividual change. One problem with these developmental research is cohort effects. A cohort is a group of
people that share the same cultural environment and historical events (baby boomers,
mil ennials). Cohort effects are differences in developmental y relevant variable that arise from
non-age related factors. The observed results are a consequence of cohort characteristics.
Investigating individuals of
Investigating the same
different ages at one point in
individual across different
points in their life.
● Economic in time
● True assessment of
● Rather cheap
● Shows similarities and
● Assessment of
stability and change of
different age groups.
● Age effects are
● Age effects can be
● No information on
effects, retest effects
and attrition effects (=
(no measure of
drop-out of subject).
other times of
● Long duration
● High costs
Cross-sectional and longitudinal designs can be combined; we can fol ow the same individuals
in different age groups over a longer period. There are different ways to measure development
● Selfreport or report by proxy in case a subject can’t answer themselves (e.g. a parent,
spouse of caregiver).
● Behavioral observation
● Standardized tests
● Experiments (e.g. memory tests)
Because there is a focus on different age groups that differ from adults, eg infants.
● Speech reception and production
● Sensomotoric abilities
● Attention span/fatigue
● Subjective meaning of concepts
● Proportion of undiagnosed clinical impairment (eg dementia)
To make sure your research goes wel , you have to adjust your methods to the abilities of the
individual. Make sure you are aware of response bias (social desirability, stereotypes etc). Why: are we who we are because of the way we are born or the way we are raised? This is the
nature vs nurture debate.
Charles Darwin focused on the nature aspect of our behavior. John Watson focused on the
nurture aspect of our behavior. Another nurturist was Bandura. He developed the social learning
theory. We learn through watching and imitating what others do. Humans have a sensitive period while developing. This means that we go through a period in
which plasticity is increased which causes us to be more sensitive to environmental stimuli. This
causes us to learn and develop. Think about language development for example. This is a link
between nurture and nature. Another interaction is genetics.
● Passive genotype-environment fit: parents design the life of their children partly.
● Evocative genotype-environment fit: own inborn characteristics that evoke certain
responses from the environment.
● Active genotype-environment fit: individuals actively select a specific environment based
on their genetic tendencies, for example: picking your university courses.
These genotype-environment fits change across your lifespan. This has to do with epigenetics. Most approaches nowadays argue that it’s a combination of nurture and nature.
Lecture 2 - Prenatal development, pregnancy, birth
What happens at conception and what are chromosomal deviances?
Conception happens around the ovulation. The egg moves down to the fal opian tube. The egg
has 24 hours to be receptive. Once fusion happens between one egg cel and one sperm cel ,
the outer layer of the egg cel hardens, and blocks the entry of other sperm cel s.
The zygote (fertilized egg) is diploid. The gametes (sperm and egg cel s) are haploid.
Each human being has 23 pairs of chromosomes, which totals to 46 in total.
Sometimes a woman happens to give birth to twins. They could either be monozygotic or
dizygotic. Monozygotic twins come from 1 egg cel and 1 sperm cel . During the cel division
they split, and grow into two different babies. They have the same genes. Dizygotic twins come
from two egg cel s and two sperm cel s. They are as equal y genetic as normal siblings, and can
even be half siblings. We have 22 autosomal (‘normal’) chomosome pairs. The 23rd chromosomes are the sex
chromosomes. The mother brings an X, the father brings either and X or Y. Therefor, the sperm
decides the gender. When chromosomes don’t develop correctly, we speak of a chromosomal deviance. Here we
discuss 3 examples.
XXY = Klinefelter syndrome: in this case someone has more X-chromosomes and one
Y-chromosome. In this case the person is male. They have a long body length and long arms
and legs. They have low testosterone, which can cause infertility or other fertility problems. The
more X-chromosomes he has, the lower the IQ. With two X-chromosomes you have a normal
IQ. Hormonal therapy can help. It’s prevalence is 1 out of 700 men.
Trisomy 21 = Down syndrome: in this case a person has (partial) three 21-chromosomes. It’s
prevalence is 15 out of 10.000 births. The older the mother is, the higher the chance that the
baby wil have trisomy 21. It is possible to get this tested before birth. These people have an
intel ectual disability, they have characteristic facial features. They are short, and have a short
life expectancy (50-60). They have an increased risk of Alzheimer’s disease. There is no cure,
only special physical training and speech therapy.
Turner syndrome: in this case a person has only one, or only one working, X chromosome.
This one usual y comes from the mother. This can be seen as the female counterpart of the
Klinefelter syndrome, as the person affected is always female. However, because they miss one
X chromosome they look less female, have fertility issues and low estrogen. They are short, with
short limbs. Their IQ remains normal. Its prevalence is 1 out of 2500 women. There are different prenatal tests to detect chromosomal deviances, apart from the standard
ultrasound. There is also a possibility to measure the nuchal fold thickness (neck). If the fold is
thicker than normal, the baby has an increased risk of cardiovascular abnormalities and down
syndrome. Another test is a blood test from the mother, to estimate the risk. Another test is CVS
(chorionic vil us sampling). There is a withdrawal of some cel s of the placenta. The risk of
miscarriage after this test is about 1%.
Nowadays there are some non-invasive prenatal test (NIPT). In week 11 you can withdraw
blood from the mother to extract DNA of the fetus. This leads to a more reliable estimation of
risk, and has no risk for miscarriage. What are the different phases of prenatal development?
● Phase 1: Germinal phase (week 0-2): the cel mass is not ful y attached to the uterine
wal yet. The zygote divides and moves down to the fal opian tube, to the uterus. The
zygote nests into the uterine wal . The zygote develops into a blastocyte. This is a
layered cel ass with a cavity.
● Phase 2: Embryonic phase (week 3-8): the blastocyte develops into the embryonic disc,
that consists of 3 layers.
a. Mesoderm: becomes muscle and the skeletal system
b. Ectoderm: becomes the skin and nervous system. The nervous system begins
with a neural tube, which folds itself into a cylinder. The upper part becomes the
brain, the lower part the spinal cord. The nervous system grows fast.
c. Endoderm: becomes the digestive and respiratory systems
In week 3 to 4 the formation of the organs (e.g. heart, so a heartbeat can be heard)
starts, and the baby hooks up to the maternal bloodstream. This facilitates growth. The
development happens inside out (proximodistal order), so first the heart and other
organs, then the limbs, and later the fingers and toes. It goes from rough to detailed. It
also goes from head to bottom (cephalocaudal order).
● Phase 3: Fetal fase (9-40 weeks): this is a slower, long refining period in which body
structures sprout. Even though the fetus looks ready after 8 weeks, the brain needs
more weeks to completely develop. It increases in size, and the brain has to fold like an
adult (sulci and gyri). This happens in a couple of steps.
a. Neurulation: formation of the neural tube
b. Neuronal proliferation: fast formation of neurons
c. Neural migration: movement of neurons to the end goals of the brain (See
The inner ear structures form by week 16. Around week 22-23 the cochlea, eardrum, ossicles
and other structures are ful y formed. The fetus has the ability to hear from now on. They can
hear their mom’s heartbeat, eating and digestion, breathing, walking, talking, exercising and
burping. They have few external visual stimuli. After 24 weeks the primary taste ability has
developed, but this develops further after birth. From 8 weeks on the fetus can respond to
touch. However, pain is observed after 24-26 weeks. The explanation for this is that the neural
system is ready around week 26, which is responsible for pain perception. A baby has a 50/50
chance of surviving by week 25. Normal y a baby is born around 38 weeks.
In the Netherlands abortion is legal until week 22 (unless there are medical reasons, than this is
stretched to 24 weeks), even though a child is viable after 22/23 weeks. This is a strong ethical
debate between choosing the child’s life and woman’s right. Most of abortions are til 8 weeks.
Lecture 3 - Infancy and toddlerhood: Physical and cognitive
Brain development in infancy
Infancy is the age range from 0 until 3 years old. After the birth the myelination (isolation of
neurons), synaptogenesis (synapse formation), synaptic pruning (synapse elimination) and
apoptosis (programmed cel death) continues.
Hebb’s law: neurons that fire together wire together. This is an important progress in learning.
Another saying is ‘use is or lose it’. When the information isn’t repeated enough, synaptic
pruning takes place, and you forget.
Another major postnatal brain process is the folding of the brain, and the development of
dendritic spreading. This is the growth of dendritic spines and the development of more
connections. This process doesn’t happen around the same time in each brain region. This is
the biological explanation for the rate of the learning and development of the infant.
Another mechanism for learning is the plasticity of the brain. This is the al owance of
adaptations of the brain as response to environmental changes, physiological changes and
experiences. Babies have the ability to learn any language in the world. They can differentiate sounds from
different non-native languages. After one year, this ability to differentiate loses is. The cause for
this is synaptic pruning. Newborn reflexes
A reflex is a involuntary and unconscious movement that is programmed by noncortical brain
regions, in response to stimuli from the environment. There are several reflexes found in
● ‘Rooting’ search reflex: newborns can search for objects (for example their mother’s
● Sucking reflex
● Grasping reflex
● Moro reflex: newborns spread their limbs al of a sudden, and then go back to normal.
This may happen when they are irritated or with a sudden sound.
● Babinski reflex: when you touch a baby’s feet, its toes wil spread apart.
● Stepping reflex
● Diving reflex: when a baby is dipped underwater, it stops breathing and the heartbeat is