Scientists around the country are logging the emotional and physical effects of negative political ads. Iacoboni tracked parts of the middle brain that lighted up in brain scans when people watched their favorite candidates come under attack. Other scientists hooked up wires to measure frowns and smiles before the meaning of the ads' words sunk in. Mostly, researchers found that negative ads tend to polarize and make it less likely that supporters of an attacked candidate will vote.
"Everyone says: 'We hate them. They're terrible,' " said George Bizer, a psychology professor at Union College in Schenectady, N.Y.
But, he added, "They seem to work."
If the choice people are making after viewing negative ads is not to vote, then the ads aren't working.