The reverse explanation is that the intelligent and studious child reads more which causes myopia. Another is that the myopic child have an advantage at IQ testing which is near work because of less eye strain. Still another explanation is that pleiotropic gene(s) affect the size of both brain and eyes simultaneously.[62] A study of Chinese schoolchildren found that after controlling for age, gender, school, parental myopia, father’s education, and books read per week, myopia was still associated with high nonverbal IQ.