Behavior is the way that animals act. For example, how do they get food or take care of their young? 1 do they find a place to live in or protect themselves 2 er? Much behavior is innate; that is, animals are born with it. However, animals learn much other behavior. There are several 3 of learned behavior. One type of learned behavior is habituation ( 习以为常 ). This happens when an animal learns to feel comfortable in a new situation and doesn’t pay attention to it anymore. For 4 , young horses are often afraid of noisy streets. But after a while they learn to pay no 5 to the normal sights and sounds of a city. 6 kind of learned behavior is conditioning. It is a way of learning by association — 7 is, by putting together different ideas. In 1990, Ivan Pavlov, a Russian biologist, studied conditioning in dogs. Dogs innately salivate ( 分泌唾液 ) when they smell food. Pavlov rang a bell every time he gave food to a dog. Soon the dog started to 8 the sound of the bell with the smell of food. After some time, it salivated 9 it heard a bell alone, without food. Learning is important for all animals in a new environment. It allows an 10 to be adaptable—that is, able to change in a new situation.