It has long been known that some plants can respond to sound. But why would a plant evolve the ability to hear? Now researchers are reporting that one reason may be to defend itself against predators. A new study suggests that response is linked to self defense. To see whether predator noises would affect plants, two University of Missouri researchers exposed one set of plants to a recording of caterpillars eating leaves, and kept another set of plants in silence. Read more in this article from The New York Times.