In a series of experiments, Dr. Arkes and his associates demonstrated how the validity effect operates. In a typical study, people read a list of statements, such as "Mercury has a higher boiling point than copper" or "Over 400 Hollywood films were produced in 1948." The participants had to rate each statement for its validity, where "1" meant that the rater thought the statement was definitely false and "7" that it was definitely true. A week or two later, they again rated the validity of some of these statements and also rated others they hadn't seen previously. The result: Mere repetition increased the perception that the familiar statements were true. The same effect also occurred for unverifiable opinions (e.g., "At least 75 percent of all politicians are basically dishonest"), opinions that people initially felt were true, and even opinions that they initially felt were false. "Note that no attempt has been made to persuade," wrote Arkes. "No supporting arguments are offered. We just have subjects rate the statements. More repetition seems to increase rated validity. This is scary."