Material:
The following appeared as part
of a letter to the editor of a scientific journal.
"A recent study of eighteen
rhesus monkeys provides clues as to the effects of birth order on an
individual's levels of stimulation. The study showed that in stimulating
situations (such as an encounter with an unfamiliar monkey), firstborn infant
monkeys produce up to twice as much of the hormone cortisol, which primes the
body for increased activity levels, as do their younger siblings. Firstborn
humans also produce relatively high levels of cortisol in stimulating
situations (such as the return of a parent after an absence). The study also
found that during pregnancy, first-time mother monkeys had higher levels of
cortisol than did those who had had several offspring."
Write a response in which you
discuss one or more alternative explanations that could rival the proposed
explanation and explain how your explanation(s) can plausibly account for the
facts presented in the argument.
Alternative Explanations:
Before making alternative
explanations for the proposed explanation and how they could account for the
facts presented in the argument, I would like to examine the facts. Then I
would like to present two explanations from two different perspectives: individual
history and social factors.
First of all, the findings of
the study are inconsistent in themselves. The last report that first-time
mothers have stronger response to stimuli shows that it is at least the
individual history rather than the birth order that affects levels of cortisol
produced by each individual. The study describes the subjects
as first-time mother monkeys, not first-time and first-born mother
monkeys, and this raises the suspicion that the study subjects include
individuals of all positions in birth order, and they all secrete high levels
of cortisol to stimuli when they have a baby for the first time, while the
first two test results show only first-born individuals, both monkeys and
humans, secrete twice as much cortisol as younger siblings. This inconsistency
allows surmise that experience of doing something first-time counts more than
being a first-child in terms of sensitivity to stimulating situations and hence
it is very much likely that effects of birth order on an individual’s levels of
reaction to stimulation do not exist.
Two alternative explanations
could be made for the test results. One is based on the mother’s individual
history affecting her first baby's physiological property. Under a plausible
condition that the condition of a mother affects the condition of her
baby, the first-born babies share the feelings of their first-time
mothers. Infant-mother relation is so close that they synchronize
emotional and physiological changes. Also, it can be easily assumed that a
first-time mother is very sensitive to her environment, as doing anything for
the first-time makes any individual nervous. Thus the contagion from the
first-time mother, who tend to be excitable to even the smallest stimulus and
produce a great amount of cortisol, makes her first-born baby react to
stimuli in the same way as its mother and produce more cortisol than its
younger siblings, whose non-first-time mothers have shared with them more
relaxed mother-and-child-hoods.
The other candidate for
alternative explanation I could come up with is based on a social factor. A
child-birth, especially the first pregnancy and birth-giving of an individual
could be a big shift of the individual’s position in the society it belongs to,
in both monkeys’ and humans'. Thus, the other individuals around the first-time
mother and her first child cannot help having interests in them and attempting
to have interaction with the new-arrival. Some adults might come near and
examine the baby, while younger individuals may watch in proximity or even
incessantly touch the baby from curiosity or animosity. Some aggressive
individual may attack the baby. This reaction from the surrounding community
may make the first-born nervous about stimulation. The babies that follow
arrive after the society has gotten used to the first child, which has
established a position in the society, and thus the second or third children
may be no more than additions that do not raise any concern in the eye of the
members of the society. Humans may also demonstrate not exactly the same but similar
reactions to first-born children and the following arrivals. Adults and
children react much more strongly to the first baby than to the second or third
ones, and the difference of the amounts of cortisol secretion between
first-born children and younger children reflects the difference of the
magnitude of the influences of these reactions of the society members to
children depending on their birth order.
Both of these explanations could
account for the facts in the study that higher production of cortisol
occurs in such a situation that first-born rhesus
monkeys encounter unfamiliar monkeys and first-born humans had higher
levels of arousal when their parents were back. Firs-time infants share
the fear which their mother monkeys have and are also nervous about
encountering other monkeys from bad experiences inflicted by others, so they
react strongly to the encounter of unfamiliar monkeys which might attack them,
and first-burn human children, who have also become highly sensitive by sharing
the anxiety of their mother and by being incessantly meddled with by the
members of their society, may react more strongly to separation from and
reunion with their parents by dramatically raising the level of cortisol in the
blood stream.
