Considering the large number of studies that have investigated the heritability of intelligence, but it is surprising that so much disagreement exists among researchers. It has been estimated that roughly half the variation in intelligence test scores is caused by hereditary influences. But it is significant that estimates of heritability can differ among ethnic and racial groups, as well as across time within a single group. Moreover, the estimates are computed, for the most part, on the basis of intelligence test scores, so that the estimates are only for that part of intelligence measured by the tests.

考虑到有大量的关于智能遗传方面的调查研究，但令人吃惊的是在研究人员中有相当多的不同意见。据估计，在智能测验分数中约有半数的变化是由于遗传的影响。但重要的是，这种遗传的评估，可因不同民族和种族群体而不同，在同一群体也可因时间不同而不同。此外，大多数评估是根据智能测验的数据计算出来的，因此这评估只适用于该部分由测验衡量出的智能。