With the advent of radio and television, presidential charisma became a more important personality characteristic. Above, Franklin Delano Roosevelt, who is rated one of the most charismatic presidents; John F. Kennedy; Bill Clinton. Getty Images hide caption

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In a 2004 debate in St. Louis, President Bush answers a question as his opponent, Sen. John Kerry, listens. Both candidates used a number of "pivots" in their debates. Ron Edmonds/AP hide caption

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Teachers interact differently with students expected to succeed. But they can be trained to change those classroom behaviors. iStockphoto.com hide caption

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A less complicated time? Petula Clark holds her 1965 gold record for "Downtown," an uptempo song in a major key. R. McPhedran/Getty Images hide caption

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Wanda Kaczynski and her son David Kaczynski (right background) are escorted to their car by defense lawyers after Unabomber Theodore Kaczynski pleaded guilty Jan. 22, 1998, in Sacramento, Calif. John G. Mabanglo/AFP/Getty Images hide caption

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Kimberly Payton, a teacher at the Small Savers Child Development Center, reads to a group of preschoolers in Washington, D.C., in 2010. Researchers say that teachers who make small changes in how they read to 4-year-olds can improve kids' reading skills later on. Ricky Carioti/The Washington Post/Getty Images hide caption

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People who are interested in and paying close attention to each other begin to speak more alike, a psychologist says. iStockphoto.com hide caption

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The antidepressant Prozac selectively targets the chemical serotonin. Paul S. Howell/Getty Images hide caption

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