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 scientific article claims that the birth order has biological effects on the production of hormone cortisol. The argument is based in some observations and experiments; however, all of them reveal examples of poor reasoning and assumptions for which there is no clear evidence. Therefore the conclusion reached by the author still unproved. Hence, the argument is unconvincing and has several flaws.

First of all, the conclusion relies in an experiment conducted with eighteen rhesus monkeys. The research project shows that firstborn infant monkeys produce much hormone cortisol that their younger brothers or sisters when they are exposed to stimulating situations. Using a sample of only eighteen monkeys seems to be really limited to drawn any general conclusion as the author does. Moreover, the author only addresses one stimulating situation, may be in any other situation such as sexual interactions or dangerous situations this rate of hormone cortisol production would change.

Secondly, the article refers to firstborn humans but any relevant figure reinforces the claim. How many firstborn human had been tested? How may not-firstborn? How the experiment was conducted? Without further information this experiment is absolutely unreliable. There could exist thousands of possible explanations for the different levels of cortisol such as different nourishing habits, illness or personal situations for the different biological response.

Finally, any relationship between the conclusion and the last argument is provided by the author. Is there any correlation between pregnant mother's cortisol levels and their child’s? If this exists is not presented in the article and, therefore, this claim is really weak and unsupported. This argument would make more sense here if firstborn mothers were found to have higher cortisol levels. In fact, it is not at all clear if other considerations had been done in during the experiment, for example, if the same mother had been tested in several pregnancies or the study is made considering different mothers at the same time, what could be an important consideration to test the reliability of the study.

In conclusion, the argument is flawed for the above-mentioned reasons and is therefore unconvincing. Many other explanations to these facts could be done and the relation between the different experiments presented in the article is not proved at all.