One of the many theories about alcoholism is the learning and reinforcement theory, which

explains alcoholism by considering alcohol ingestion as reflex response to some stimulus and as a way to reduce an inner drive state such as fear or anxiety. Characterizing life situations in terms of approach and avoidance, this theory holds that persons tend to be drawn to pleasant situations or repelled by unpleasant ones. In the latter case, alcohol ingestion is said to reduce the tension or feelings of unpleasantness and to replace them with the feeling of euphoria generally observed in most persons after they have consumed one or more drinks.

Some experimental evidence tends to show that alcohol reduces fear in an approach - avoidance Situation. Conger trained one group rats to approach a food goal and, using aversive conditioning, trained another group to avoid electric shock. After an injection of alcohol the pull away from the shock was measurably weaker, while the pull toward food was unchanged.

The obvious troubles experienced by alcoholic persons appear to contradict the learning theory in the explanation of alcoholism. The discomfort, pain, and punishment they experience should presumably serve as a deterrent to drinking. The fact that alcoholic persons continue to drink in the face of family discord, loss of employment, illness, and other sequels of repeated bouts is explained by the proximity of the drive reduction to the consumption of alcohol; that is, alcohol has the immediate effect of reducing tension while the unpleasant consequences of drunken behavior. come only later, Tile learning paradigm, therefore, favors the establishment and repetition of the resort to alcohol.

In fact, the anxieties and feelings of guilt induced by the consequences of excessive alcohol ingestion may themselves become the signal for another bout of alcohol abuse. The way in which the cue for another bout could be the anxiety itself is explained by the process of stimulus generalization: Conditions or events occurring at the time of reinforcement tend to acquire the characteristics of stimuli. When alcohol is consumed in association with a state of anxiety or fear, the emotional state itself takes on the properties of a stimulus, thus triggering another drinking bout.

The role of punishment is becoming increasingly important in formulating a cause of alcoholism based on the principles of learning theory. While punishment may serve to suppress a response, experiments have shown that in some. cases it can serve as a reward and reinforce the behavior. Thus if the alcoholic person has learned to drink under conditions of both reward and punishment, either type of condition may precipitate renewed drinking.

Ample experimental evidence supports the hypothesis that excessive alcohol consumption can be learned. By gradually increasing the concentration of alcohol in &inking water, psychologists have been able to induce the ingestion of larger amounts of alcohol by an animal than would be normally consumed. Other re- searchers have been able to achieve similar results by varying the schedule of reinforcement; that is, by requiring the animal to consume larger and larger amounts of the alcohol solutions before rewarding it. in this manner, animals learn to drink enough to become dependent on alcohol in terms of demonstrating withdrawal symptoms.

The author maintains that habituation to excessive alcohol consumption can be learned.The method employed to do so, experimentally, which used reinforcement is ______.

A．the introduction of alcohol into the bloodstream by infection

B．the increase of the concentration of alcohol in the subject's drinking water

C．the use of anxiety in an avoidance - approach pattern

D．increasing the amount of alcohol the subject must drink each time before giving it a reward