This study investigated whether the environment created by being born in a specific birth order and/or family size affects individuals genetic intelligence, or g. Based on the phenomenon of rising IQ scores between generations, the fact that IQ and g are correlated and that nearly all between-family variables have been shown not to produce the rising effect, it was hypothesized that there could be a significant difference in g scores of siblings of the same family and those of different sized families born in the same position. Birth order and family size could be argued to encompass most...