Stupid people make us dumber

From the Washington Post, there is a reference to the work...

...of two Cornell scientists who showed that one attribute of extreme incompetence is "that the person so afflicted is incapable of knowing that he is incompetent." The study, titled "Unskilled and Unaware of It," demonstrated that people who scored, on average, at the 12th percentile in tests of humor, grammar and logic assessed themselves to be, on average, at the 62nd percentile. Incompetence at the extreme is a double-whammy, the authors declare: "Not only do these people reach erroneous conclusions and make unfortunate choices, but their incompetence robs them of the metacognitive ability to realize it." (Which explains Washington, in a nutshell.)

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Scientific conclusion: Stupid people make us dumber.