The Effect of Schooling on Cognitive Skills
利用瑞典男性兵役前认知测试日期的条件随机变化，发现额外10天学校教育使晶体智力测试得分提高约1%标准差，而流体智力测试得分不受影响。
To identify the causal effect of schooling on cognitive skills, we exploit conditionally random variation in the date Swedish males take a battery of cognitive tests in preparation for military service. We find an extra ten days of school instruction raises scores on crystallized intelligence tests (synonyms and technical comprehension tests) by approximately 1 percent of a standard deviation, whereas extra nonschool days have almost no effect. In contrast, test scores on fluid intelligence tests (spatial and logic tests) do not increase with additional days of schooling but do increase modestly with age.