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 situ

The author's argument that the birth order plays a significant role in determining an individual's stimulation levels may seem to be logical at first glance. The argument could be correct,if its premises were to be true. However, the author has used certain assumptions in building his argument for which there is no clear evidence.

The author has studied the eighteen rhesus monkeys and based on the study he has concluded that, the birth order has a significant affect on an individual's stimulation level. Through his study he has found that firstborns exhibit higher levels of stimulation under unexpected circumstances. The first evidence to support his conclusion is that the firstborn infant monkeys produce up to twice as much of the hormone cortisol, which prepares the body for increased activity levels, as do their younger siblings. This evidence cannot be accepted in its entirety as the author has listed only one stimulating situation(an encounter with an unfamiliar monkey). He does not explicitly talk about any other stimulating situation. The author considers the production of cortisol as an indication of increased stimulation. However,there could be other causes of production of this hormone, the author has not thrown any light on this fact. The author has based his conclusion on only one set of 18 monkeys. The affect observed here,could be common to this particular group or species of monkeys. Unles the experiment is done with more groups and species such evidence cannot be accepted at face value.

The author also provides other evidence stating that firstborn humans also produce relatively high levels of cortisol in stimulating situations (such as the return of a parent after an absence). In this case, the author fails to mention the source of his information. Author has simply stated the evidence like a well established fact. He may be quoting a valid research article, however he has not provided any information which proves the credibility of the source from where he has gleaned this information.

The author's study also states that during pregnancy, first-time mother monkeys had higher levels of cortisol than did those who had had several offspring. This evidence does not lend any support to the author's argument. Since, here the author does not state that the increased cortisone levels in first time mothers has to do anything with them being firstborns too. So it is not a supporting evidence at all. An alternative explanation of his study could be that, the mothers are very protective of their firstborns. As a result the firstborns are used to a higher level protection than later offsprings. As a result, the firstborns exhibit a higher degree of insecurity when faced with an unexpected situation, hence the increased cortisone levels.

Summing up,the author's conclusion could be correct if his assumptions and evidences are based on solid facts and credible reserches. The evidences under present condition are not enough to make his argument accepted as valid.