1. Several Conventional Criteria

There are five main criteria of abnormality. They are:

1. Statistical Criterion
2. Social Criterion
3. Personal Discomfort (Distress)
4. Maladaptive Behavior
5. Deviation from Ideal

Abnormal behaviors are "actions that are unexpected and often evaluated negatively because they differ from typical or usual behavior".^[1]

The following Criteria are subjective:

• Maladaptive and Malfunctional behaviors. Behaviors, which due to circumstance, are not fully adapted to the environment. Instead, they become malfunctional and detrimental to the individual, or others. For example, a mouse continuing to attempt to escape when escape is obviously impossible.^[2]
• Behavior that violates the standards of society.^[3] When people do not follow the conventional social and moral rules of their society, the behavior is considered to be abnormal. (See Deviation from Social Norms)
• Observer discomfort.^[4] If a person's behavior brings discomfort to those in observation, it is likely to be considered abnormal.

The standard criteria in psychology and psychiatry is that of mental illness or mental disorder. Determination of abnormality in behavior is based upon medical diagnosis.

Other Criteria

• Statistical Infrequency: Statistically rare behaviors are called abnormal. Though not always the case, the presence of abnormal behavior in people are usually rare or statistically unusual. Any specific abnormal behavior may be unusual, but it is not uncommon for people to exhibit some form of prolonged abnormal behavior at some point in their lives.^[5]
• Deviation from Social Norms: Behavior that is deviant from social norms is defined as the departure or deviation of an individual from society's unwritten rules (norms). For example, if one was to witness a man jumping around, nude, on the streets, the man would likely be perceived as abnormal to most people, as he has broken society's norms about wearing clothing. There are also a number of criteria for one to examine before reaching a judgment as to whether someone has deviated from society's norms. The first of these criterion being culture; what may be seen as normal in one culture, may be seen as abnormal in another. The second criterion being the situation & context one is placed in; for example, going to the toilet is a normal human act, but going in the middle of a supermarket would be most likely seen as highly abnormal, i.e., defecating or urinating in public is illegal as a misdemeanor act of indecent public conduct. The third criterion is age; a child at the age of three could get away with taking off clothing in public, but not a man at the age of twenty. The fourth criterion is gender: a male responding with behavior normally reacted to as female, and vice versa, is often likely to be seen as abnormal or deviant from social norms. The fifth criterion is historical context; standards of normal behavior change in some societies, sometimes very rapidly.
• FF: Failure to Function Adequately is a behavior that is abnormal, and indeed these criteria are necessary to label an abnormality as a disorder, if the individual is unable to cope with the demands of everyday life.^[6] Psychologists can disagree on the boundaries that define what is 'functioning' and what is 'adequately', however, as some behaviors that can cause 'failure to function' are not seen as bad. For example, firemen risking their lives to save people in a blazing fire may be ‘failing to function’ in the fact that they are risking their life, and in another context their actions could be construed as pathological, but within the context of being a firefighter said risks are not at odds with adequate functioning.
• DIM: Deviation from Ideal Mental health defines abnormality by determining if the behavior the individual is displaying is affecting their mental well-being. As with the Failure to Function definition, the boundaries that stipulate what 'ideal mental health' is are not clearly defined. A frequent problem with the definition is that all individuals at some point in their life deviate from ideal mental health, but it does not mean the behavior is abnormal. For example, someone who has lost a relative is distressed and deviates from "ideal mental health" for a time, but their distress is not defined as abnormal, as distress is an expected reaction.^[7]

A common approach to defining abnormality is a Multi-Criteria approach, where all definitions of abnormality are used to determine whether an individual's behavior is abnormal. For example, psychologists would be prepared to define an individual's behavior as "abnormal" if the following criteria are met.

• The individual is engaging in behavior that is preventing them from functioning.
• The individual is engaging in behavior that breaks a social norm.
• The individual is engaging in behavior that is statistically infrequent.

A good example of an abnormal behavior assessed by a multi-criteria approach is depression: it is commonly seen as a deviation from ideal mental stability, it often stops the individual from 'functioning' a normal life, and, though it is a relatively common mental disorder, it is still statistically infrequent. Most people do not experience significant major depressive disorder in their lifetime.^[8] Thus, depression and its associated behaviors would be considered abnormal.