Readiness to make a particular response to a stimulus situation; there are motor sets, perceptual sets, and mental sets. The term is usually reserved for temporary or recently developed readiness to react, in contrast to habit, which is a long-established, persistent readiness to respond in a definite way.At any moment we are bombarded by many stimuli, but our set predisposes us to select and respond to one or another of them. It therefore structures and gives meaning to the situations we meet. For example, in reading we set ourselves to deal with the printed page and ignore incidental sounds coming from the street, the pressure of the chair on our body, and a multitude of other stimuli. Sets of this kind are learned from past experience, although practice and training can strengthen them considerably. A sprinter, for instance, can be coached to attend only to the sound of the starter’s gun and to establish the muscular set he needs for a fast start. See reaction time.Readiness to react to the sound of a starting gun or the sight of a traffic light are examples of motor set. This type of set involves postural adjustments made during the act of attending to or watching for a certain stimulus. When we start a race we crouch, tense our muscles, and bend forward; when we are listening for a very faint sound, we protrude our head and breathe through our mouth in order to make less noise. Sometimes this readiness to react can be overdone and misfire: the runner may make a false start when he hears a noise from the grandstand, and the patient in a dentist’s chair may respond to the drill before he feels any pain.The second type, perceptual set, is a readiness to register and perceive certain stimuli. A doctor may be set to hear the telephone during the night; his wife, to awaken when their baby cries. When we see our favorite comic on the stage, we are usually set to laugh—and we may not laugh nearly so hard at an equally funny comedian we have never seen before. (See Fig. 20, p. 465: if you are set to see a vase, you will see it—and the same for two faces. This principle applies also to Fig. 21, p. 465.) This type of set may also misfire. If we are waiting for a friend on the street comer, we may react to someone in the distance who only slightly resembles him. If we are hungry, we may mistakenly think the sign “Rest Room” says “Restaurant.” This point has been demonstrated by withholding food from groups of subjects for one, four, and sixteen hours, then showing them a dimly lighted screen depicting objects or people in action. The hungrier the subjects were, the more they interpreted the ambiguous stimuli in terms of food or eating (McClelland and Atkinson, 1948).A mental set, on the other hand, is a selective process which determines the way we think or solve problems. If you ask a person to pronounce Mac- tavish, Macdonald, Macbeth, and Machinery, he will usually say MacHinery for the last one instead of machinery. Similarly, if you ask him to think of four-letter words ending in -any he will probably say many, zany, etc., but if you then ask him to give a four- letter word ending in -eny he will run into trouble. The -any words will prevent him from finding the solution (deny) because he is set for a certain pronunciation. This suggests that rigid mental sets frequently interfere with our thinking processes. Getting away from the problem often helps us break this set and approach it from a new angle. On the other hand, mental sets can be helpful in keeping our minds “on target.” Sets of all three kinds can be influenced by a number of factors. First, definite instructions are usually effective: the quarterback gives certain signals which get the team set for a certain play. Experiments have shown that even general instructions such as, “Get out of the usual rut. Think freely. Try all possibilities,” will often facilitate the solution of a problem. Second, arousing motivation or providing incentives will often promote the desired set: for example, showing a succulent roast beef in a window of a restaurant will bring in customers. Third, intense, changing, or contrasting stimuli will enhance our readiness to respond: a large, illuminated sign in red letters going on and off will be more likely to start us thinking about the product than a less arresting sign.The concept of set has innumerable applications. It determines the type of reaction we make to both situations and people: the optimist sees obstacles as temporary setbacks, while the pessimist sees them as proof of failure. It helps to account for many of our social attitudes: the prejudiced person is set to judge a whole group by one objectionable individual, while the tolerant person will realize that unpleasant people can be found in all groups. Likewise, a stereotype is actually a form of set—for example, the “miserly Scot,” or the “reserved Englishman.” Emotionally disturbed people are particularly “set in their ways”; one man will react aggressively in almost every situation, another will be hypersensitive to the slightest rebuff or hint of criticism, and still another will be suspicious of everyone he meets.Finally, set is deeply involved in our learning and mental processes. Tests have shown that the most efficient way to study is to be “primed” in advance on what to look for and what is important. The student’s motivational set can also make a great difference. If he sets himself to learn the material permanently, he will not readily forget it— but if he sets himself to retain it only long enough to pass an examination, it will fail to “sink in” and stay with him.