GRE- rhesus monkeys The passage proposes a correlation between individual’s levels of stimulation and the birth order both in rhesus monkeys and human beings, as well as the times of pregnancy for mother monkeys. However, as some important details are not provided by the author, the results of the experiment cannot convincingly justify such a conclusion. There are some alternative explanations for the results that might weaken the author’s arguments. The firstborn infant monkeys produce more cortisol than their younger siblings may due to their age rather than their birth order, given the possibility that older monkey are more mature in the development of physical organs such as brains, which enable them to better perceive the potential dangerous situation thus have a more vigilant reaction. It may also be possible that the quantity of the hormonie produced is not only related to the degree of stimulation relation. We cannot exclude the possibility that the older the monkey is, the more production of hormone regardless of the levels of stimulation. These alternative explanations are the same when apply to human beings. Besides, the stimulation experiments for monkey and for human are different, as “a unfamiliar monkey” is a negative stimulation and the “return of parents” is the positive one. What if the first born children are more emotionally depend on their parents since they feel that the care their parents give them is somehow distracted by their younger sibling? In this point we should also be susceptible. Also, the hypothesis of the correlation between the times of pregnancy and the simulation level of mother monkeys might be weakened by other alternative explanation. The higher levels of cortisol the first-time mother monkey produce might due to its physical mechanism as reaction of pregnancy. It might be possible that when the body gets used to the “pregnancy”, it would gradually decrease the hormone it produces as the monkeys have experimented the second, third, of fourth time of pregnancy. Additionally, there is another alternation that the decrease of hormone has nothing to do with the pregnancy, as it might be the age that influence the production of the cortisol. Since the passage does not provide us with detailed information about the control of sample in the research, we might hypothesize the age as the real factor of cortisol production.