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The Rhesus Monkeys Argument - With A Free Essay Review
"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."
In this argument the writer believes that birth order has effects on an individual's levels of stimulation. To support this claim, the writer cites evidence: a recent study of eighteen rhesus monkeys, the study on the firstborn humans and the study of mother monkeys during pregnancy. But I think all these studies may have no relation to the claims.
In the study of the eighteen rhesus monkeys, I assume that the observed data are statistically significant. Producing twice as much of the hormone cortisol doesn't indicate that there is a relation with birth order; an alternative explanation to that offered by the letter writer is that this case is caused by other factors such as the number of the monkeys in the stimulating situation. If the experiment makes the firstborn infant monkey stay in the stimulating situation alone, while the siblings stay together, it will probably cause the different levels of hormone cortisol.
In the study on the firstborn humans, I think the higher levels can also be explained differently. One explanation is that maybe in this experiment, the time of the absence is not controlled to be the same, and the firstborn humans produce higher levels of cortisol is due to the longer absence. Then the conclusion of the arguer cannot be credible because of the flaw in the study.
Also, there is an alternative explanation for the study of the mother monkeys. It is obvious that all the mother monkeys are younger during their first pregnancy than during later pregnancy. So all the mother monkeys share the younger age, which may be the factor that causes the higher levels of cortisol. If so, the conclusion derived from the study will be doubtable.
From the alternative explanations I have given, the argument looks very doubtable, and there are lots of things the arguer need to do to strengthen the argument.
Your first argument here offers what I think is a fairly weak alternative explanation for the results of the study because the explanation depends on the speculation that the study was just badly designed; in any reasonable study, the testing conditions would be the same for each animal studied. There is little value in speculation of this kind because there is no limit to the scope of possible speculation.
The second argument suffers from the same problem as the first.
The third argument does not rely on speculation in the same way as the first two arguments, which is good. But it's not clear here to what explanation you are offering your explanation as an alternative. The fact that the original letter mentions that first-time mother monkeys had higher levels of cortisol is either a red herring in the original letter or is by implication an attempt to explain what the reported fact about firstborn monkeys (their higher levels of cortisol in stimulating situations) might have to do with the order of birth (e.g., the mother's cortisol level is related to the infant's cortisol level). To say that the first-time mother's younger age "causes the higher levels of cortisol" is plausible, but not clearly an alternative explanation to anything that is explained (explicitly or implicitly) in the letter.
If we assume that the author of the letter is indeed suggesting that the higher levels of cortisol in first-time mothers goes hand in hand with higher levels of cortisol in firstborn infant monkeys, then a plausible alternative might be to suggest that cortisol levels are purely circumstantial and have nothing to do directly with whether an infant is the first born or not. For example, it may be that the first born monkeys in the study, just because they are the older monkeys in the family (and not precisely because they happen to be born first), may reasonably expect more play, or fights, when another monkey comes along. That is, perhaps the result is a function of age and not birth order. To test this, we would need then to see how much cortisol the younger siblings produced in similar circumstances once they reached the same age as the older monkeys had reached at the time of the original study).