>"The study looked at the IQ scores of brothers who were born in different years. Researchers found that, instead of being similar as suggested by a genetic exp

>"The study looked at the IQ scores of brothers who were born in different years. Researchers found that, instead of being similar as suggested by a genetic explanation, IQ scores often differed significantly between the siblings." I can think of a multitude of reasons younger siblings should, on average, have a lower IQ than their older brothers. Could this independently account for the 'decline' that researchers are measuring?