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.
1.调查样本数量少
2.草率推广（猴+人->个体）
3.因果关系错，他因导致刺激水平差异
The conclusion that birth order is related to individual’s levels of stimulation seems to be logical at first glance. After all, it is based on recent study which examines the levels of cortisol of infant monkeys and humans and also mother monkeys. However, the argument is unpersuasive with the absence of explanation for several details in the study.
Firstly, the mere sample of eighteen monkeys is too limited to illustrate that firstborn infant monkeys have a higher level of cortisol than their younger siblings. It is entirely possible that all the eighteen monkeys come from the same region and the fruits or water there contain special chemical composition which cause a high cortisol level in order monkeys. In this case, we can not draw the conclusion that monkey’s cortisol level is related to birth order. Thus we had better enhance the quality of the sample in order to adjust for any untypical statistics and make the argument more convincing.
Even if we have enough random samples, the argument is still questionable with a hasty generalization. As we know, monkeys and humans have a lot in common, such as body structure and behavioral habits. But both of them are different with other spices like fish, bird and insect. It may be the case that the relationship between birth order and stimulation level is only a characteristic of mammal or even only monkeys and humans instead of all the individuals. Without a much more widely study or a clear definition of individual, the conclusion is always open to question.
Finally, the author ignores a myriad of other possible reasons for a higher stimulation level, for example, individual differences such as personality and cognitive level. It is possible that the firstborn monkey is more outgoing than the younger one. When they encounter with an unfamiliar monkey, the order one shows more active than the younger one. It is also possible that the younger one is too young to recognize its parents, so that when a parent return after an absence, the younger one is not as happy as its order brother. Thus, we can not ascribe the level of stimulation to birth order until we can rule out all the other possible reasons.
Overall, we need more alternative explain to improve the argument, such as how to get a quality sample, how to define the range of individuals and how to rule out other possible reasons. In addition, the author should also provide the relationship between the cortisol level of mother monkeys and their kids to confirm that his/her last experiment can support the argument. | 
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发表于 2012-5-15 17:45:57
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