Birth Order - an overview
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.
While it may be true that offspring's cortisol production depends on birth order, the author does not explain the correlation between birth order and exact cortisol decrement. The author's argument is full of biases and cannot make the proper connection between clues.
The author reports firstborn infants produce twice cortisol relative (in comparison with) to younger siblings. However, the author doesn't explain the hormone reduction trend in following sibling. Perhaps there are no differences at the hormone production level between second and third born monkey. As far as this variation is not examined, it is impossible to issue a general rule for the effect of birth order.
The author implied that because of the firstborn humans' high-level cortisol production, the firstborn infant monkeys also will obey this relation. Although some similarities founded between monkey tribes and human, and it could encourage scientist to investigate more evidence to prove the assumption, it is not enough to convince the editor of the scientific journal.
Additionally, the author mentions another finding that first-time pregnant monkeys had a higher level of cortisol relative to who had several offspring. Although this is another clue to prove the study, the exact increment of cortisol remains vague and ambiguous. The final result of the study must be certified by running the analytical tests on data, for example, a t-test, to show that the higher level of hormone is significant and reliable.
This study discovers important clues to prove the assumption but there were some logical fallacies in explanation to persuade the editor of the scientific journal.