1 Demography Unit, Department of Sociology, Stockholm, Sweden.
2 Center for Cultural Evolution, Stockholm University, Stockholm, Sweden.
Proc Biol Sci. 2019 May 15;286(1902):20190359. doi: 10.1098/rspb.2019.0359.
We examine the relationship between cognitive ability and childbearing patterns in contemporary Sweden using administrative register data. The topic has a long history in the social sciences and has been the topic of a large number of studies, many reporting a negative gradient between intelligence and fertility. We link fertility histories to military conscription tests with intelligence scores for all Swedish men born 1951-1967. We find a positive relationship between intelligence scores and fertility, and this pattern is consistent across the cohorts we study. The relationship is most pronounced for the transition to a first child, and men with the lowest categories of IQ scores have the fewest children. Using fixed effects models, we additionally control for all factors that are shared by siblings, and after such adjustments, we find a stronger positive relationship between IQ and fertility. Furthermore, we find a positive gradient within groups at different levels of education. Compositional differences of this kind are therefore not responsible for the positive gradient we observe-instead, the relationship is even stronger after controlling for both educational careers and parental background factors. In our models where we compare brothers to one another, we find that, relative to men with IQ 100, the group with the lowest category of cognitive ability have 0.56 fewer children, and men with the highest category have 0.09 more children.
我们利用行政登记数据研究了当代瑞典认知能力与生育模式之间的关系。这个话题在社会科学领域有着悠久的历史，也是许多研究的主题，其中许多研究报告称智力与生育率呈负相关。我们将生育史与瑞典所有 1951-1967 年出生男性的兵役征兵测试中的智力分数相关联。我们发现智力分数与生育率之间存在正相关关系，而且这种模式在我们研究的队列中是一致的。这种关系在第一次生育的过渡中最为明显，智商得分最低的男性生育的孩子最少。使用固定效应模型，我们还控制了所有兄弟姐妹共有的因素，经过这些调整后，我们发现智商与生育之间的正相关关系更强。此外，我们还发现在不同教育水平的群体中存在正梯度关系。因此，这种构成上的差异并不是我们观察到的正梯度的原因——相反，在控制了教育生涯和父母背景因素后，这种关系甚至更强。在我们将兄弟之间进行比较的模型中，我们发现，相对于智商为 100 的男性，认知能力最低类别的男性生育的孩子少 0.56 个，而认知能力最高类别的男性生育的孩子多 0.09 个。
