| > Such claim would have been relevant if each kid of an age class (or at least several thousands, in various countries) is asked to pass an IQ test. Assuming that IQ stays constant throughout the life. The earliest comprehensive national survey I’m aware of is the Scottish 1932 one[1]. Most countries with conscription/the draft administer an IQ test like the ASVAB in the US. So in the Nordic countries you have going on a century of data covering basically the entire male population at 18. IQ becomes more stable across life. The younger a child is the more likely it is that any given test is a bad estimate of their adult IQ, which will basically be stable taking into account age related cognitive decline[2]. [1] Population sex differences in IQ at age 11: The Scottish mental survey 1932 There is uncertainty whether the sexes differ with respect to their mean levels and variabilities in mental ability test scores. Here we describe the cognitive ability distribution in 80,000+ children—almost everyone born in Scotland in 1921—tested at age 11 in 1932. There were no significant mean differences in cognitive test scores between boys and girls, but there was a highly significant difference in their standard deviations (P<.001). Boys were over-represented at the low and high extremes of cognitive ability. [2] Intellectual Development from Early Childhood to Early Adulthood: The Impact of Early IQ Differences on Stability and Change over Time Intellectual ability of about 200 individuals was first assessed between the ages of four to twelve years, and subsequently at the ages of 17 and 23. Stability of general intelligence was found to be moderately high for the entire study period. Stability was higher for shorter intervals between measurement points and increased with age. Subgroup analyses for initially high-, average-, and low-IQ children revealed that IQ stability over time was higher for the low-IQ than for the high-IQ children. Overall, participants with initially higher IQ scores maintained their advantage throughout the study until the period of early adulthood, and were more likely to attend higher educational tracks. |