Another story on birth-order effects, this time in Slate.
The problem with this study can be summarized in one of the authors’ sentences: While the data does not contain complete information on grades, it does include information on mothers’ perceptions of their children.*
This is supposed to be a contribution by the authors to the scientific study of birth order effects. But this is a highly contested field. And in this scientific debate, there is one whole side loudly protesting that claims about birth-order effects are exaggerated, and that they have no measurable influence on how people turn-out as adults. Many birth-order critics suggest that birth-order studies really only measure how parents perceive their children. Essentially, they say, birth order studies just reconfirm something we already know – parents tend to view kids a certain way depending on whether they were first born. This affects the relationship between parents and kids, and (birth-order critics would add) nothing else.
The question is – the thing being contested – is whether birth-order can be shown to have an impact on levels of education, affluence, achievement, etc. in adults (after controlling for parental affluence, family size, and some other factors).
So reading this article, and the study on which it is based, you almost can’t believe your eyes when you see that the primary data set is simply maternal perceptions of their kid’s educational success. Guess what? Mom’s tend to think first-borns are doing better in school than latter-borns.
Other than that, this high impressionistic data is a mess. Why are second-borns in two child families perceived by their mothers to be as educationally successful as first-borns in three-child families? Why are second-borns in three-child families perceived to be so much less successful than second-borns in four-child families? Who knows, and ultimately who cares if you aren’t going to grapple with the big issue of whether or not this stuff matters beyond parental perception?