A process in which new information, habits, or abilities are acquired; in general, any modification of behavior due to contact with the environment.Animals and human beings are in constant interaction with their surroundings, but they may be said to learn only when certain criteria are met. The major hallmarks of learning are: (1) the contact with the environment must bring about a change in the way they think, perceive, or respond; (2) this change must come about as a result of observation, practice, study, or other activity, and not by such conditions as fatigue, drugs, illness, or maturation; (3) the modification of behavior must be relatively lasting—a fact or a skill that is forgotten right after it has been acquired is not really learned. At the present time the only way we can know that anything is actually learned is by observing a change in performance—by noting that the person can ride a bicycle or recite a poem better than he could before. We do not as yet know what changes take place in the organism when learning occurs, but this information will probably be acquired as we learn more about the nervous system.Man is more dependent on learning than the lower animals, partly because his life is more complex and partly because his behavior is less fully determined by reflexes, instincts, and physiological drives. The human being does not come into the world nearly so well equipped as the animal to satisfy his needs and cope with the situations he meets. He has to go through a prolonged infancy and childhood during which he must acquire complex habits, skills, problem-solving ability, and communication patterns which are not needed by any other organism. He even has to learn how to learn. In this whole process he also has a much greater chance than lower animals to acquire undesirable responses, and therefore must go through a great deal of relearning as well.In spite of present ignorance of the physiological mechanisms involved, the field of learning is one of the most thoroughly studied in the whole of psychology. It covers widely different areas of experience, including motor skills like typing or factory operations; complex activities like piano or chess; attitudes, such as prejudices and feelings about capital punishment or war; social behavior, including customs and occupational or class roles; verbal learning, as in studying literature or memorizing names and dates; and the acquisition of emotional responses, such as sympathy, fear, or resentment. Each of these types will be discussed under separate headings. See CATEGORY INDEX.At present it is not known whether a common set of principles applies to all these forms of learning, or whether there are several different principles. Many psychologists, however, have attempted to find a single basic concept, such as drive reduction or conditioning, which would cover the entire process. At the moment it appears that there are many different techniques for learning.On the other hand, there is considerable agreement on many of the practical aspects of the learning process. These, too, will be reviewed under separate topics, particularly LEARNING TECHNIQUES and MEMORY IMPROVEMENT, but it might be useful to mention some of the major points in this general article. Motivation is one of the most important keys to learning, ft is doubtful if any organism learns unless it is impelled by a need, faced with a problem, or lured by a reward. Moreover, increasing the motivation usually enhances the learning. Practice and repetition are generally needed to advance the learning process and make it “stick.” In verbal learning this takes the form of active recitation and periodic review. It has been found that learning periods and practice periods are usually more effective when they are spaced than when they are close together. Also, it is often but not always better to break up complex or lengthy subject matter and work on it piecemeal than to try to learn it all at once. Since there is a danger of “missing the forest for the trees” it is usually best to go through the entire material quickly before studying or practicing the details. This will provide a frame of reference and give the entire process more meaning—and the more meaningful the material is, the easier it is to learn and the longer it will stay with us.