I've seen this study before and while its certainly measuring something, what its measuring doesn't seem to fit the definition of IQ. Considering it says that younger children score higher when under 12 then vice versa, IQ isn't really suppose to be changeable especially at that kind of age.
The social expectations on the first born may cause them to concentrate harder perhaps, who knows. And while its a large sample its from a particular source that may include systematic biases. If smarter younger kids managed to get out of military service in disproportionate numbers that would skew the results.
The social expectations on the first born may cause them to concentrate harder perhaps, who knows. And while its a large sample its from a particular source that may include systematic biases. If smarter younger kids managed to get out of military service in disproportionate numbers that would skew the results.