阅读理解　All the characteristics and abilities a person acquires and all developmental changes result from two basic, though complex, processes: learning and maturation. Since the two processes almost always interact, it is difficult to separate their effects from each other or to specify the relative contribution of each to a child''s development. Clearly, growth in height is not learned but depends on maturation, a biological process. But improvements in motor activities such as walking, depend on maturation and learning, and the interaction between them. 　　What, then, are maturation and learning? Developmental psychologists are not entirely in agreement, though there is a common core of accepted meaning. Thus all definitions of maturation stress organic processes or structural changes occurring within an individual''s body that are relatively independent of external environmental conditions, experiences, or practice. By maturation it is meant development of the organism as a function of time, or age. 　　Learning has also been defined in diverse ways, but the term generally refers to changes in behavior or performance as a consequence of experience. Learning is the process by which an activity originates or is changed through training procedures as distinguished from changes not attributable to training. 　　A number of important and stimulating theories of learning have been proposed, each with its own set of principles and hypotheses for explaining the learning process. For our purposes, we do not need to be concerned with the specific details of the learning process, even though learning plays the most important role in most aspects of development and change. We shall employ only a few generally accepted principles of learning in this discussion. 　　Specifically, we accept the principle that a child will learn a response more effectively and more thoroughly if he is motivated to learn it. Moreover, he will learn a response better if he is rewarded for learning it. According to this view, the more a response is rewarded, the stronger it becomes and the more likely it is to be repeated. Although most learning involves motivation and reward, I believe some learning does occur without them. 　　As for the interrelationships between maturation and learning process, a general principle may be provided: maturation is essential to learning.