This is the 2007 version. Click here for the 2017 chapter 12 table of contents.

Defining Abnormal Behavior

When starting a discussion of abnormal behavior, students sometimes ask, "How can anybody tell what is abnormal, anyway?" There are several different criteria that can be used:

What are some of the different ways to define abnormal behavior?

1. Statistical abnormality. A behavior may be judged abnormal if it is statistically unusual in a particular population.

2. Violation of socially-accepted standards. An abnormal behavior might be defined as one that goes against common or majority or presumed standards of behavior. For example, one might be judged abnormal in one's failure to behave as recommended by one's family, church, employer, community, culture, or subculture.

3. Theoretical approaches. Theories approach abnormality by starting with a theory of personality development, If normal development can be defined, then abnormality is defined by the failure to develop in this way. For example, if adults normally arrive at a moral stage that prohibits killing other people, and someone does not arrive at this stage, that person might be called abnormal.

4. Subjective abnormality. Abnormal behavior can be defined by a person's feeling of abnormality, including feelings of anxiety, strangeness, depression, losing touch with reality, or any other sensation recognized and labeled by an individual as out of the ordinary.

5. Biological injury. Abnormal behavior can be defined or equated with abnormal biological processes such as disease or injury. Examples of such abnormalities are brain tumors, strokes, heart disease, diabetes, epilepsy, and genetic disorders.

What are limitations of the "statistical abnormality" approach?

Each definition has its uses and its limitations. A statistical definition of abnormality is precise (one can collect data and show how common or uncommon a particular behavior is in a particular group) but it does not correspond well to what people call abnormal. Many rare behaviors, such as collecting old books, are not considered abnormal.

What is the main limitation of the "violation of social standards" approach?

Violation of socially accepted standards is another common and widely used definition of abnormality. By this definition, a person is abnormal if violating the expectations and values of a community. For example, watching TV may be considered abnormal in the Amish culture, where modern conveniences are avoided. Violation of standards does not necessarily correlate with statistical rarity. Physical abuse of a spouse is considered abnormal in the United States, although it occurs in up to a fifth of marriages. The main problem with the "violation of standards" definition of abnormality is that it is based upon cultural standards that change from place to place and time to time. What is abnormal in one culture may be regarded as acceptable in a different culture. What is regarded as abnormal at one time may be regarded as normal several decades later.

What is wrong with using subjective discomfort as a criterion of abnormality?

Judging abnormality by subjective discomfort raises a different set of problems. Psychotic people, the most seriously disordered of all mental patients, often feel perfectly normal and suffer little distress, despite having markedly "crazy" and unrealistic thought processes that could lead to behavior harmful to themselves or others.

Biological approaches to defining abnormal behavior are based on detecting a disease or disorder of the nervous system. Many of the classic psychiatric syndromes we will discuss in this chapter are now recognized as brain diseases involving abnormal levels of neurotransmitters, the chemicals that neurons use to communicate. On the other hand, people tend to refer to any behavior they do not like as a disease or a disorder. The idea that alcoholism is a disease, for example, is quite controversial, although it is a widely accepted idea.

Why is the "disease" approach to defining abnormal behavior gaining ground?

Biological approaches to defining abnormal behavior of many types seem to be gaining ground, because there are so many advancing technologies for defining biological problems. Brain scans, analysis of neurotransmitters, and genetic analysis all provide objective ways of identifying biological disturbances. The vast majority of abnormal behaviors discussed in this chapter (with a few exceptions such as the personality, somatoform, and factitious disorders) are now thought to have a biological basis. Many respond to medication, used alone or with psychotherapy.

What is the risk of overemphasizing biological factors?

Even when there are biological factors that contribute to a problem, the environment usually plays a role as well. Biological approaches to defining abnormality may encourage people to overlook environmental factors that are easier to change than genetics or brain disorders. A study of adopted children showed that two distinct risk factors encouraged alcoholism: (1) familial alcoholism (one or both genetic parents were alcoholic) and (2) drinking in the family environment (the adoptive parents had drinking problems) (Cadoret, O'Gorman, Troughton, and Haywood, 1985). Either heredity or environment could increase risk of alcoholism, and obviously only the environment can be manipulated or changed after a person is born, if one wants to prevent alcoholism from developing.

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