Scientists search for the biology of smarts
Nearly a century ago, British psychologist Charles Spearman started what remains one of the most passionate debates about people's mental abilities. Spearman declared in 1904 that he had found the way to measure an individual's core intelligence. Using a mathematical method called factor analysis, Spearman noted that individuals score similarly on many items from a range of mental tests, some resembling today's IQ tests. Scores on these correlated items yielded a single factor, which Spearman called the general or g factor, that he deemed to be a marker of a person's facility for reasoning about any and all mental tasks.
Although Spearman had difficulty defining precisely what g measured or how it worked, he regarded it as mor