I have a theory...

[[Cl...]]

Deep, I am not smart, I am just curious  , very interesting replies indeed.

Hurt, I fully agree with you in the case of the oldest children  While my theory of the one before the youngest when 3 or more children was that I think they are the smartest of the family. But Megan got to the point, it may be a family thing. The "only child" case may be attributed to the fact that all the family eyes are looking at she/he. I am just guessing, I work with postgrad students and most of them are either the oldest (highly responsible persons, work very hard, independent...) or the one before the youngest child (the most clever students). It is not a rule of course, just a tendency. Then I thought, well, the good students are different from the normal boys and girls, that is why I thought on asking this question in here.

Thank you all!