Noise affects human behavior. In one experiment carried out by psychologists, a student leaving a library intentionally dropped an armload of books. In 50% of the cases, a passerby stopped to help the student pick up the books. Then the experimenters brought out a lawn mower without a muffler and started it near where a student would again intentionally drop the books. This time, only about 10% of the people who passed stopped to help. It was clear that behavior changed because of the earsplitting sound of the nearby lawn mower. In experiments in Los Angeles, researchers found that children who lived in neighborhoods near the airport could not complete certain tasks undertaken when jets were landing and taking off as easily as children who lived in quiet neighborhoods. Some studies of prison conditions have shown that the high level of noise causes more complaints by prisoners than the food or other prison conditions do.