Scott Alexander debunks a study claiming Victorians were smarter than modern people, showing it's based on flawed data comparison and ignores crucial factors like selection bias and demographics. Longer summary

Scott Alexander critiques a study claiming Victorians were more intelligent than modern people based on reaction time measurements. He argues the study's conclusion is flawed due to significant selection bias in the Victorian data, which primarily came from wealthy, educated individuals. The modern data, in contrast, was more representative of the general population. Scott points out that the difference in reaction times can be explained by sampling from the top 20% of Victorian society versus a broader modern sample. He also highlights how the study ignores important factors like race and regional variations in IQ, which could further account for the observed differences. Scott concludes by urging readers not to cite this study as evidence for declining intelligence or civilization. Shorter summary