Number of Siblings and Personality

Are children from small [U.S.] families advantaged and those from large families disadvantaged other factors being equal?...Our results indicate that the assumption that children from smaller families are less sociable than children from larger families is weak and is confounded by other factors. Rather the results suggest that on average those from more advantaged socioeconomic backgrounds are less sociable and those from small families are more frequently from advantaged backgrounds. Data are from various published sources. (EXCERPT)