A principle of learning which states that to establish an association between two events, they must be experienced close together in time and space.The principle explains how we learn that thunder follows lightning, that fire is hot, or which word follows which in memorizing a poem. It also applies to classical conditioning in which a previously neutral stimulus takes the place of the original stimulus in producing a response. In all these instances two events are repeatedly associated in time, place, or both, and this establishes a connection between them in our minds. As a result, the first becomes a signal for the second—that is, when lightning flashes, we wait to hear the thunder. It is important, however, to emphasize the closeness of the association. If thunder followed lightning after a long interval, we would not readily associate them. Likewise, if the old and new stimuli are more than one half second apart in conditioning the experiment rarely works.Contiguity is particularly applicable in learning a sequence of any kind (serial learning). When we recite a speech or play a composition on the piano, each response becomes a stimulus for the response that was contiguous with it in the original learning situation. “Four score and” brings to mind “seven,” which in turn calls forth “years ago” and so on. We also make practical use of this principle in jogging our memory. If we have mislaid a pair of gloves, we attempt to reconstruct our activities in sequence; and if we cannot remember a historical fact, wetry to think of other events that occurred at the same time or place. Sometimes we have to go through a long chain of associations before we succeed in recalling the fact we want. A similar technique is sometimes used in restoring the memory of amnesia victims. See AMNESIA (DISSOCIATIVE TYPE).Although contiguity is undeniably important in explaining the learning process, many investigators believe it does not work by itself. They point out that another factor is required before learning occurs: motivation. Both animals and human beings appear to learn most effectively when their learning is rewarded or “reinforced.” A material reward is not always necessary, for a word of approval or even intrinsic satisfaction of curiosity may be sufficient reinforcement. Intention also appears to be a motivating force, particularly in human learning. In meeting a person for the first time, we glance at his face and hear his name, but we may not establish an association unless we have the intention of learning his name (and even then we may fail to recall it). This suggests that there is a certain amount of selectivity in establishing associations between contiguous events. On the other hand, some psychologists maintain that we also acquire many incidental facts without any need or motivation. See INCIDENTAL LEARNING, CONDITIONING, STIMULUS-RESPONSE ASSOCIATION, STIMULUS-STIMULUS ASSOCIATION, ASSOCIATIONISM, PAIRED ASSOCIATES LEARNING, REINFORCEMENT