Answer: Suspense and tension.
Explanation:
In 1938, Orson Welles made an adaptation of the novel "War of the Words", by H. G. Wells. The adaptation was broadcasted on the radio and, disputably, caused some panic among listeners.
Welles chose to make the story sound as if it were real news. So, from time to time, the music program that was on would be interrupted by a news bulletin narrating updates from the observatory at Princeton. The listeners were told explosions had been observed in Mars, a strange object had fallen on Earth, and so on.
For many decades, such broadcast was believed to have caused great panic. People would have taken to the streets, yelling that the world was ending, stealing and then running for their lives. Nowadays, however, it is said that such panic never occurred or did so in a much smaller scale. The radio show wasn't very popular or, at least, not popular enough to reach a large number of people and cause a riot of some sort.
