2018年4月21日托福阅读机经预测

　　Animal Behavior

　　By the early 1900s the field of animal behavior had split into two major branches. One branch, ethology,developed primarily in Europe. To ethologists, what is striking about animal behaviors in that they are fixed and seemingly unchangeable? For example, kittens and puppies play in characteristic but different ways. Present a kitten with a ball of yarn and invariably it draws back its head and bats the yarn with claws extended. Kittens are generally silent as they play, and their tails twitch. Puppies, by contrast, are most likely to pounce flat-footed on a ball of yarn. They bit and bark and their tails wag. Ethologists came to believe that ultimately even the most complex animal behaviors could be broken down into a series of unchangeable stimulus/response reactions. They became convinced that the details of these patterns were

　　as distinctive of a particular group of animals as were anatomical characteristics. For well over half a century, their search for and description of innate patterns of animal behavior continued.

　　2 Meanwhile, mainly in North America, the study of animal behavior took a different tack, developing into comparative behavior. Of interest to comparative behaviorists was where a particular came from, that is, its evolutionary history, how the nervous system controlled it, and the extent to which it could be modified. In 1894, C. Lloyd Morgan, an early comparative behaviorist, insisted that animal behavior be explained as simply as possible without reference to emotions or motivations since these could not be observed or measured. In Morgan’s research, animals were put in simple situations, presented with an easily described stimulus, and their resultant behavior described.

　　3 The extension to animals of behaviorism—the idea that the study of behavior should be restricted to only

　　those elements that can be directly observed—was an important development in comparative behavior. Studies of stimulus/response and the importance of simple rewards to enforce and modify animal behavior were stressed. Not surprisingly, comparative behaviorists worked most comfortably in the laboratory. Comparative behaviorists stressed the idea that animal behavior could be modified, while their ethologist colleagues thought it was innate and unchangeable. Inevitably, the two approaches led to major disagreements.

　　4 To early ethologists, the major driving force in behavior was instinct, behaviors that are inherited and unchangeable. ■ Moths move towards light because they inherit the mechanism to so respond to light. ■ Although dogs have more options available to them, they bark at strangers for much the same reasons. ■ The comparative behaviorists disagreed: learning and rewards are more important factors than instinct in animal behavior. ■ Geese are not born with the ability to retrieve lost eggs when they roll out the nest, they learn to do so. If their behavior seems sometimes silly to humans because it fails to take new conditions into account, that is because the animal’s ability to learn is limited. There were too many examples of behaviors modified by experience for comparative behaviorists to put their faith in instincts