RUTH: What was the problem with most of these studies, do you think?
ED: I think it was because in a lot of cases data was collected from only one sibling per family, who rated him or herself and his or her siblings at the same time.
RUTH: Mmm. Some of the old research into the relationship between birth order and academic achievement has been proved to be accurate though. Performances in intelligence tests decline slightly from the eldest child to his or her younger siblings. This has been proved in lots of recent studies.
ED: Yes. Although what many of them didn’t take into consideration was family size. The more siblings there are, the likelier the family is to have a low socioeconomic status – which can also account for differences between siblings in academic performance.
RUTH: The oldest boy might be given more opportunities than his younger sisters, for example.
ED: Exactly.
RUTH: But the main reason for the marginally higher academic performance of oldest children is quite surprising, I think. It’s not only that they benefit intellectually from extra attention at a young age – which is what I would have expected. It’s that they benefit from being teachers for their younger siblings, by verbalising processes.
2/2