Lectures Early development
Week 1
Lecture 1 Biology and prenatal environment
Biology and/or environment
How much is nature and how much is nurture? People differ in meaning about this issue.
- Behaviorism is advocate of nurture: the environment is the supreme force in child
development.
- Bee example of nurture: same DNA, but different diet leads to different function of
the bees.
- Human example of nurture: with the same child there is improvement possible with
an enriched profile/situation. But there is a range with each child (range of reaction).
- Nature: Genes influence that you are in a certain way, e.g. down syndrome. These
characteristics of the infant shape the environment. For example, shape the way how
people respond to the child.
The question is not whether biological or environmental factors are more important,
but it is more about how the expression of our biology is shaped by the environment we
meet (=programming).
Early in life there are critical and sensitive periods in which the environment has bigger
impact on the person than in later life.
- Critical period: if you are exposed to a certain environment, that environment can
only have impact in a certain time window and the effects are irreversible.
- Sensitive period: environment shapes a given trait or behavior to a larger extent than
in other periods or stages. Early life in itself is a sensitive period. There is more
plasticity in early life. This is for a reason, because you can adapt to the environment
you will encounter in later life. But this provides some risks for the development, like
if you are exposed to risky environments. But it can also provide chances.
First 1000 days: refer to early life; from conception until more or less the second birthday.
- DOHaD hypothesis: environment during critical or sensitive periods may have
significant consequences on an individual’s short and long-term health.
Model of Hanson and Gluckman is showing on the green line normal development, with an
increase of chronic disease during life course. In later life it has only a little impact. But if you
do something in early life, the risk is reduced way more than when you do something in later
life. So early life is important for intervening and has a big influence for development in early
life.
To find out how big the role is of nature and nurture, many do adoption studies and twin
studies.
- Identical twins have similar IQ, even when reared apart. Evidence that nature is more
important for IQ.
, - But if you look further, the IQ of parent/child and foster parent/child are also quite
correlated in the same amount. So maybe nurture play a role.
Question: identical twins have identical genes. So, if reared apart, any similarities they have
must be due to shared genes?
Chorionic arrangements
Answer on the question is false.
- Identical twins already share the prenatal environment (the womb). But one child can
get more nutrition/oxygen than the other.
- So even if identical twins are reared apart (different situations), they already share
the first prenatal environment. How much this is similar between the twins, depends
on the chorionic arrangements.
Chorionic arrangements:
- Dichorionic twins: separate placentas and fetal circulations. Can be identical or
fraternal.
- Monochorionic twins: one placenta and one fetal circulation. Can only be identical
twins. These are more similar then the dichorionic twins in e.g. personality,
schizophrenia. Even in the monochorionic twin, it could be that one child gets more
nutrition than the other.
Prenatal development
Development is going quickly in early life. Much is happening in the first trimester. Toxics can
already have an effect on the infant, and that happens for example when women don’t know
they are pregnant.
Placenta transfers nutrients from the mother to the baby, and transfers wasted from the
baby.
Pregnancy is a sensitive period. Toxic agents that can harm the child are called teratogens.
These are agents that can cause structural malformations early in pregnancy (e.g. missing
limbs) and later in pregnancy more problem with growth can occur and mental and cognitive
problems.
Example of a drug called thalidomide. These caused malformations to the limbs/missing
limbs: phocomelia. This was not so long ago, then the research on drugs for pregnant
women were not sufficient.
These are observational studies and often if you want to investigate humans (what toxic
agents has an influence) that is through observational studies. Or often turn to animal
research. What is very important is prenatal diet.
Study of prenatal diet with animals:
- Pregnant rats which were given a normal diet or a poor diet (low in energy). After
pregnancy the pups were given two types of diets (normal or very fatty diet, that is
also a poor diet but because it is so rich in calories).
, - Found that the ones who were on poor diet during pregnancy, they did very poorly in
comparison with a normal diet (200 days difference). And if you also give them the
fatty diet, they even live shorter. The difference is way bigger in the lifespan in
prenatal diet. So prenatal diet is very important, but the lifespan decreases more
when you also give them a fatty diet after pregnancy.
- Why is this latter thing? -> bodies from poor diet pups are able to work with the little
energy they get. If they are exposed to a rich diet after pregnancy, that is completely
different and then there is a mismatch.
Match-mismatch model: Explains how a developing fetus adapts in anticipation of the
postnatal environment, as a result of cues experienced prenatally. If you are in pregnancy
exposed to a poor diet, you expect that after birth there will also be not much food around
(so adaptation to a poor diet environment). So, your body is programmed to work with the
food that you get. This will increase your changes for survival but also increase the
reproducing success.
This provides evidence that we are very plastic. Plasticity is very great in early life. This
enables us to adapt and if we don’t adapt, we can never work with a changing environment.
So, plasticity is very costly and maybe the key to the success of humans.
This developmental mismatch is a cost of our developmental plasticity. So, if we are
exposed to certain cues during pregnancy, the change is likely that the environment after
birth will be the same (and not change dramatically). Often prenatal environment is a good
predictor of how the postnatal environment is. But in cases where this is not the case, you
will see this mismatch and that is the cost of our developmental plasticity. The risk of being
so plastic. But the benefits are still higher than the costs, so developmental plasticity will
occur.
Example that is comparable to the mice situation, is the Dutch hunger winter:
- Lead to many people dying but also many people affected. Also, many women
conceived in this period or they were pregnant. So, you can compare these groups.
Video Tessa Roseboom is exam material. Especially the results:
- Investigate the effects of starvation upon pregnancy.
- The birthweights were lower of the babies that were born during this period.
- Included babies who were born around this period in this study.
- Two control groups: babies born before the famine and conceived after (unexposed
entirely).
- Different experimental groups: late (born during the famine), mid (conceived before
the famine and born after), early (conceived during the famine and born well after).
- Results: both boys and girls are lighter when exposed to famine in late or mid stage.
But interestingly, for the early stage they had normal birth weights. Probably because
the mothers were better fed during the second and third trimester of pregnancy.
- Follow-up results: babies who were exposed to famine in early stage, they had
normal birth weights. But they have more lipid profile, disturbed clotting factors and
doubled rates of cardiovascular disease/mortality.
, Conclusion: famine exposure had
huge effects on later health, and these
effects are dependent on its timing
(before, late, mid, early, after). And the
effects of famine are independent of
size at birth (so not mediated through
birth weight). Especially early stage is a
sensitive period.
Conclusion: timing of exposure
matters! If you compare the ones who
were exposed to the famine in the first
trimester this was most detrimental.
And the ones that were mid or late
stadium they also had lower birth weights and glucose tolerance.
Prenatal stress
Can stress also affect the development of the offspring? Distress is a combination of stress
and anxiety and to a lesser extent depression. How can you study prenatal stress? (1) ask
mothers, (2) investigating exposure to life events during pregnancy, (3) investigating
exposure to natural disasters.
1: Ask the moms using questionnaires: around 10% meet criteria for a mental disorder. But if
you look at symptoms and self-reports, the percentages are much higher. So, is there an
underestimation? If you do research with self-report and you follow the children much
research has done about this.
When stress, child outcomes were higher negative affectivity and related to behavior
problems and reduced cognitive developments.
What are pros and cons of the research investigating prenatal stress using self-report:
- Advantage: it is easy and doesn’t cost much time.
- Disadvantage: it is subjective, social desirability, if you are very stressed this can
influence how you answer the questions about child outcomes (if you are very
stressed it feels like your baby is crying a lot, even though that is not), if you ask
about subjective stress it is more or less stable so you can’t do very good research on
the timing.
2: Other ways to look at stress in order to overcome the problem of timing is investigate
exposure to life events during pregnancy. Include life events such as death of a relative or
life-threatening illness.
Children more often have adhd symptoms and behavior problems. Cognitive problems
were not prominent.
3: You can also look at moms that are suffering from a natural disaster during pregnancy.
This happened suddenly, so the time before that was relatively stress free. But difficult if it
was the disaster or maybe something associated with the disaster that “caused” the effects.
Project Ice Storm. Exam material:
