Why IQ scores rose so fast that 1900s Americans would seem mentally impaired today
In short: James Flynn, a moral philosopher turned intelligence researcher, discovered a startling trend: IQ scores have been rising globally for decades. Because this shift happened too quickly for genetic evolution, Flynn argued that environment, not biology, is the primary driver of intelligence, fundamentally changing how we understand human cognitive potential.
James Flynn, an American-born New Zealand academic, spent his career challenging the notion that intelligence is primarily genetic. While researching a refutation of classical racism in 1978, he analyzed historical IQ data and noticed a persistent anomaly. Although tests were recalibrated to keep the average score at 100, raw performance was steadily improving. Flynn calculated that the average American from 1900 would score a 67 on a 2000-era test, a result that would have been classified as mentally impaired.
This phenomenon, later dubbed the 'Flynn effect' by authors Richard Herrnstein and Charles Murray in their 1994 book The Bell Curve, demonstrated that IQ gains were too rapid to be explained by genetics. Flynn argued that environmental factors—such as modernization and improved education—were the true catalysts. He bolstered this by examining Raven's Progressive Matrices, a non-verbal test designed to measure fluid intelligence, which showed consistent gains across 14 nations between 1932 and 1978.
Flynn’s work was not without controversy. He frequently debated figures like Arthur Jensen and J. Philippe Rushton, who argued for genetic explanations of group differences in IQ. Despite these clashes, Flynn maintained mutual respect for his opponents and advocated for open scientific debate. He posited that the Black-White IQ gap was largely environmental, suggesting that if the average environment for Black Americans in 1995 matched the quality of the average environment for White Americans in 1945, the gap would close.
Later in his career, Flynn and economist William Dickens proposed a model of two-way causality: a challenging environment raises an individual's IQ, and a higher IQ makes it more likely that an individual will seek out or be placed in more cognitively demanding environments. While recent research suggests the Flynn effect may have plateaued in some developed nations, his work remains a cornerstone in the study of human intelligence, forcing a global reassessment of what IQ tests actually measure.
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- Summary by Intellect · source: James Flynn (academic)
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