First-borns might score higher on measures of intelligence, because, at some point in their lives, they were only children who were the sole recipients of their parents' attention.

研究人员称，先出生的孩子们之所以在智力测试上得分更高，是因为在生活的某一个阶段，他们是独生子女，故而能够独享父母的关爱。