Introduction
Motivation refers to a group of variables that determine what behavior—and how strong and how persistent a behavior—is to occur. Motivation is different from learning. Learning variables are the conditions under which a new association is formed. An association is the potential for a certain behavior; however, it does not become behavior until motivation is introduced. Thus, motivation is necessary to convert a behavioral potential into a behavioral manifestation. Motivation turns a behavior on and off.
Incentive motivation is an attracting force, while drive motivation is an expelling force. Incentive is said to “pull” and drive to “push” an individual toward a goal. The attracting force originates from the reward object in the goal and is based on expectation of the goal object in certain locations in the environment. The expelling force originates from within organisms as a need, which is related to disturbances in homeostasis in the body. The two forces jointly determine behavior in a familiar environment. In a novel environment, however, there is not yet an expectation; no incentive motivation is yet formed, and drive is the only force to cause behavior. The organism can be expected to manifest various responses until the goal-oriented responses emerge.
Once the organism achieves the goal, the reward stimuli elicit consummatory responses. Before the organism reaches the goal, the stimuli that antedate the goal would elicit responses; these are termed anticipatory goal responses. The anticipatory responses are based on the associational experience among the goal stimuli, the goal responses, and the situational stimuli present prior to reaching the goal. The anticipatory responses and their stimulus consequences provide the force of incentive motivation. Incentive refers to the expected amount of reward given certain behavior.
Though drive motivation and incentive motivation jointly determine behaviors, the importance of each differs for different behaviors. For example, bar-pressing behavior for drinking water by an animal in a Skinner box normally requires both drive motivation, induced by water deprivation, and the incentive motivation of a past experience of getting water. Under special conditions, however, the animal will press the bar to drink water even without being water deprived. In this case, drinking is no longer related to drive. This type of drinking is called nonhomeostatic drinking. Drinking a sweet solution, such as one containing sugar or saccharin, does not require any deprivation, so the behavior to get sweet solutions is based on incentive motivation alone. Under normal conditions, sexual behavior is elicited by external stimuli, so sexual drive is actually incentive motivation elicited from without.
Behavior and Incentives
Two experiments will illustrate how the concept of incentive motivation may be applied to explain behavior. Carl J. Warden of Columbia University conducted a study that is regarded as a classic. A rat was placed in the start box of a short runway, and a reward (food) was placed in its goal box at the other end. The food-deprived animal had to cross an electrified grid on the runway to reach the goal. When the animal reached the goal, it was repeatedly brought back to the start box. The number of times the animal would cross the grid in a twenty-minute period was recorded. It was found that the longer the food deprivation, the more times the animal crossed the grid, for up to about three days without food, after which the number decreased. The animal crossed only about two times with no food deprivation; however, the number increased to about seventeen at three days of food deprivation, then decreased to about seven at eight days without food. When the animal was water deprived, the animal crossed the grid about twenty times to the goal box containing water at one day without water. When the reward was an infant rat, a mother rat crossed about twenty times. A male rat crossed about thirteen times to a female rat after being sex deprived (without a female companion) for one day. A female rat in heat crossed thirteen times to a male rat. Even without any object in the goal box, the animal crossed about six times; Warden attributed this to a “novelty” reward. The reward variable in this experiment was the goal object, which was manipulated to fit the source of the drive induced by deprivation or hormonal state (as in an estrous female). The rat, placed in the start box, was induced by the goal.
Crespi Effect
The second study, conducted by Leo P. Crespi, established the concept of incentive motivation as an anticipatory response. He trained rats in a runway with different amounts of food and found that the animals reached different levels of performance. The speed of running was a function of the amount of reward: The more the food in the goal box, the faster the animal would run. There were three groups of rats. Group 1 was given 256 food pellets (about a full day’s ration) in the goal box; the animals would run at slightly over 1 meter (about 3.28 feet) per second after twenty training trials. Group 2 was given 16 pellets, and their speed was about 76 centimeters (2.5 feet) per second. Group 3 was given only 1 pellet, and the speed was about 15 centimeters (6 inches) per second.
When the speed became stable, Crespi shifted the amount of food. The rats in all groups were now given 16 pellets. The postshift speed eventually, but not immediately, settled to near that of the group originally given 16 pellets. An interesting transitional effect of so-called incentive contrast was observed. Immediately after the shift from the 256-pellet reward to the 16-pellet reward, the animal’s speed was much lower than the group continuously given the 16-pellet reward. Following the shift from the 1-pellet to the 16-pellet reward, however, the animal’s speed was higher than the group continuously given the 16-pellet reward. Crespi called these the elation effect and the depression effect, or the positive contrast effect and the negative contrast effect, respectively. Clark L. Hull and K. W. Spencer, two of the most influential theorists of motivation and learning, interpreted the Crespi effect as evidence of anticipatory responses. They theorized that the goal response had become conditioned to the runway stimuli such that the fractional goal responses were elicited. Because the responses occurred before the goal responses, they were anticipatory in nature. The fractional goal responses, along with their stimulus consequence, constitute the incentive motivation that would energize a learned associative potential to make it into a behavior.
Manipulation of Motivation
Incentive motivation has been manipulated in many other ways: the delay of reward presentation, the quality of the reward, and various partial reinforcement schedules. In relation to the delay variable, the sooner the reward presentation follows the responses, the more effective it is in energizing behavior, although the relationship is not linear. In the case of partial reinforcement, when the subject received a reward only part of the time, behavior was shown to be more resistant to extinction than when reward was delivered every time following a response; that is, following withdrawal of the reward, the behavior lasted longer when the reward was given only part of the time than when the reward was given every time following the response. The quality of the reward variable could be changed by, for example, giving a monkey a banana as a reward after it had been steadily given raisins. In Warden’s experiment, the various objects (water, food, male rat, female rat, or rat pup) placed in the goal box belong to the quality variable of incentive. Another incentive variable is how much effort a subject must exert to obtain a reward, such as climbing a slope to get to the goal versus running a horizontal path.
Intracranial Self-Stimulation
The term “ reinforcer” usually indicates any stimulus that would result in increasing the probability or magnitude of a response on its presentation following that response. When the response has reached its maximum strength, however, a reinforcer can no longer increase it; nevertheless, it has a maintenance effect. Without it, the response would soon cease. A reward reinforces and maintains a response. It is believed that the rewarding effects are mediated by the brain; the mechanism that serves as the substrate of the effects has been studied.
In a breakthrough experiment in this line of study, in 1954, James Olds and Peter Milner reported that a rat would press a bar repeatedly to stimulate certain areas of its brain. (If the bar press resulted in stimulation of certain other areas of the brain, the rat would not repeat the bar press.) Thus, this particular brain electrical stimulation has a rewarding effect. The phenomenon is termed intracranial self-stimulation. The rewarding effect is so powerful that the hungry animal would rather press the bar to stimulate its brain than eat. It has also been shown that animals will press a bar to self-inject cocaine, amphetamine, morphine, and many other drugs. The rewarding effect is so powerful that if rats or monkeys are given access to a bar that allows continuous self-administration of cocaine, they often die of an overdose. It is now known that the neurotransmitter involved in this rewarding effect, as well as in the rewarding effect of food, is dopamine, acting at the nucleus accumbens, a part of the limbic system in the brain. Addictions and drug-directed behaviors can be understood better because of studies related to the brain reward mechanism. This mechanism is defined as the rewarding effect of various stimuli, such as food, cocaine, and intracranial self-stimulation, as related to dopamine activity in the brain. Whether incentive motivation is mediated by the same brain mechanism can also be studied.
Achievement Motivation
In humans, achievement motivation
can be measured to predict what a subject would choose to do given tasks of different difficulty as well as how persevering the subject will be when he or she encounters failure. Achievement motivation is related to past experiences of rewards and failures to obtain a reward, so it becomes an incentive motivation of anticipating either success or failure to obtain a reward. Fear of failure is a negative motivational force; that is, it contributes negatively to achievement motivation. Those people with a strong fear of failure will choose easy tasks to ensure success, and on encountering failure they will give up quickly.
Unless an individual anticipates or believes that the effort will lead to some desired outcome, the person will not expend much effort. Expectancy theory
states that how much effort a person will expend depends on the expected outcome of the effort. If the expected outcome is positively correlated to the effort, the person will work as hard as possible. In a classroom setting, effort can be evaluated from a student’s attendance, note taking, and discussions with classmates or teachers. The expected outcome would be to earn a particular grade, as well as perhaps to obtain a scholarship, make the dean’s list, obtain a certain job, gain admission to graduate school, or gain respect from peers and parents. Unless the effort is perceived to be related to the outcome, little effort will be expended.
If one is expecting a big reward, one would work harder than if the reward were small. An Olympic gold medal is worth harder work than a school gold medal is. Anyone can affect other people’s behavior with proper incentive; behavior can be manipulated to promote learning in students and promote productivity in industry. The way incentive is used to promote productivity distinguishes the free enterprise system based on a market economy from a socialist society of controlled economy which is not based on market force. In a socialist economy, one’s reward is not based on the amount of one’s economic contribution; it is based on the degree of socialistic behavior. One’s political background, in terms of family, loyalty to the party, and “political consciousness,” are the things that matter most. It is difficult or impossible to predict, under this kind of reward situation, what kinds of activities will be reinforced and maintained. The expected outcome of an individual’s effort or behavior is the incentive motivation; teachers and managers must understand it to promote desired learning and production. For example, an employee will be motivated to perform certain tasks well by a pay raise only when he or she perceives the relationship between the effort and the raise. A student will be motivated to study only when he or she sees the relationship between the effort and the outcome.
Relationship to Pleasure
The concepts of incentive, reward, and reinforcement originated with the concept of pleasure, or hedonism. The assumption that a major motivation of behavior is the pursuit of pleasure has a long history. Epicurus, a fourth century b.c.e. Greek philosopher, asserted that pleasure is good and wholesome and that human life should maximize it. Later, Christian philosophers asserted that pleasure is bad and that if a behavior leads to pleasure it is most likely bad as well. John Locke, a seventeenth century British philosopher, asserted that behavior is based on maximizing anticipated pleasure. Whether a behavior would indeed lead to pleasure was another matter. Thus, Locke’s concept of hedonism became a behavioral principle. Modern incentive motivation, based on anticipation of reward, has the same tone as Locke’s behavioral principle. Both traditions involve the concepts of incentive and of reinforcement being a generator of behaviors.
There is a danger of circularity in this line of thought. For example, one may explain behavior in terms of it resulting in obtaining a reward, then explain or define reward in terms of behavior. There is no new understanding to be gained in such circular reasoning. Fortunately, there is an independent definition of the rewarding effect, in terms of the brain mechanism of reward. If this mechanism is related to pleasure, there could also be a definition of pleasure independent of behavior. Pleasure and reward are the motivating force, and anticipation of them is incentive motivation. Because it attracts people toward their sources, by manipulating the sources, the behavior can be predictably altered.
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