Definitions of Abnormality

Statistical infrequency defines a behaviour as abnormal if it is statistically rare — a long way from the average in a normal distribution of scores across the population.

In a normal distribution, most people cluster around the mean and the numbers thin out towards the extremes. A characteristic counts as abnormal if it sits in one of these rare tails, usually beyond two standard deviations from the mean.

The clearest real example is IQ. Average IQ is set at 100, and about 95% of people score between 70 and 130. A score below 70 places someone in the bottom ~2% of the population, and this cut-off is used in diagnosing intellectual disability disorder.

Statistical infrequency: a behaviour is abnormal if it lies far enough from the statistical average to be rare in the population.

Limitation — rarity is not the same as a problem. The definition treats any rare score as abnormal, but it says nothing about whether that rarity is desirable. A very high IQ (above 130) is just as statistically infrequent as a very low one, yet we would not call a genius "abnormal" in the sense of needing help. The cut-off point is also arbitrary: there is no natural reason the line falls at 70 rather than 72. Statistical rarity alone cannot tell us who actually needs support.

Deviation from social norms defines a behaviour as abnormal if it breaks the unwritten rules and expectations a society holds about how people should behave. Every society sets standards — often moral standards — for acceptable conduct, and someone who steps outside them is judged abnormal.

A textbook example is antisocial personality disorder. A key feature is a lack of guilt or empathy alongside aggressive, sometimes deceitful behaviour. Because most societies expect people to feel remorse and to respect others, this pattern deviates from the expected moral behaviour of the group and is classed as abnormal.

Deviation from social norms: a behaviour is abnormal if it violates the shared, usually unstated, rules of acceptable conduct within a society.

Limitation — norms are culturally and historically specific. What one society calls abnormal, another calls normal, and standards change over time. The most powerful example is homosexuality, which was classified as a mental disorder in diagnostic manuals until the 1970s and is now recognised as a normal variation of human behaviour. Because the definition depends on prevailing social values, it can be used as a tool of social control — labelling people who are simply different as "abnormal" — and it carries a clear risk of cultural bias when norms from one culture are applied to another.

Failure to function adequately defines a behaviour as abnormal if a person can no longer cope with the ordinary demands of everyday life — holding down work, maintaining relationships, self-care, and basic daily routines.

Rosenhan and Seligman (1989) proposed a set of signs that suggest someone is failing to function. When several are present, it becomes reasonable to judge behaviour as abnormal:

Sign of failing to function	What it looks like
Personal distress	The person suffers, e.g. deep anxiety or despair
Maladaptive behaviour	Behaviour that works against the person's own interests
Irrationality	Behaviour that others cannot understand or make sense of
Observer discomfort	The behaviour makes other people feel uncomfortable
Unpredictability	Sudden, unexpected behaviour out of proportion to the situation
Violation of moral standards	Breaking the accepted moral or social codes of the community

Failure to function adequately: a behaviour is abnormal if the person cannot meet the everyday demands of living, shown by signs such as personal distress and maladaptive behaviour.

Limitation — it is subjective, and normal lives can look dysfunctional. Someone has to decide whether a person is coping, and that judgement is subjective — what feels like "failing" to an observer may be a deliberate, functional lifestyle choice (living off-grid, an unconventional career). Equally, entirely normal reactions can look like dysfunction: intense grief after a bereavement shows distress and maladaptive behaviour, yet it is a healthy human response, not a disorder.

Deviation from ideal mental health flips the question round. Instead of asking what makes someone abnormal, Jahoda (1958) asked what perfect mental health looks like, then defined abnormality as failing to meet those criteria.

Jahoda set out six criteria for ideal mental health. Learn all six — dropping any of them weakens an exam answer:

1. Positive self-attitudes — having self-esteem and a positive view of yourself.
2. Self-actualisation — growing and reaching your full potential.
3. Autonomy — being independent and able to act on your own judgement.
4. Resistance to stress — coping effectively with stressful situations.
5. Accurate perception of reality — seeing the world in a realistic, undistorted way.
6. Environmental mastery — meeting the demands of situations and adapting to your circumstances.

Deviation from ideal mental health (Jahoda, 1958): a person is abnormal if they fail to meet the six criteria for ideal mental health.

Limitation — the bar is impossibly high, and culturally loaded. The criteria are so demanding that almost no one meets all six at once; by this standard, most of the population would be classed as abnormal at some point. The criteria are also culturally biased: values like autonomy and self-actualisation reflect Western, individualist cultures, and would look self-centred in more collectivist societies that prize interdependence over independence.

No single definition of abnormality is complete. Each one captures something real, but each is undermined by a clear weakness — which is exactly why the exam rewards you for pairing every description with its limitation.

Definition	Core idea	Key example	Main weakness
Statistical infrequency	Abnormal = statistically rare	IQ below 70	Arbitrary cut-off; ignores desirable rare traits
Deviation from social norms	Abnormal = breaks society's rules	Antisocial personality disorder	Culturally and historically relative; risks social control
Failure to function adequately	Abnormal = cannot cope with daily life	Rosenhan and Seligman's signs	Subjective; grief and non-standard lives look dysfunctional
Deviation from ideal mental health	Abnormal = fails Jahoda's six criteria	Missing autonomy or self-actualisation	Standards almost no one meets; Western cultural bias

Two threads run across the whole topic. First, cultural relativism: social norms and Jahoda's criteria both depend on the values of a particular culture, so behaviour judged abnormal in one place may be normal in another. Second, subjectivity and arbitrary cut-offs: statistical infrequency and failure to function both rely on a line drawn by someone, and where that line falls is a matter of judgement rather than fact.

In real diagnosis, clinicians rarely rely on one definition alone. A judgement usually draws on several criteria together — for example, combining personal distress (failure to function) with a statistically rare pattern of behaviour — because each definition is stronger at covering the gaps left by the others.

The strongest exam answers do not pick a single "best" definition. They show that the definitions work as a set: each is useful, each is limited, and together they give a fuller picture than any one on its own.

1. Giving a definition without its limitation

Most marks in this topic come from evaluation. Stating what statistical infrequency is earns the description marks, but leaving out its weakness (arbitrary cut-off, ignores desirable rare traits) caps your score, so pair each definition with at least one limitation.

2. Forgetting that statistical infrequency includes desirable rare traits

A very high IQ is just as statistically infrequent as a very low one. The classic point to make is that rarity alone cannot define abnormality, because some rare characteristics are positive and clearly do not need treatment.

3. Confusing deviation from social norms with deviation from ideal mental health

They sound similar but work in opposite directions. Social norms judges you against society's external rules of behaviour. Ideal mental health judges you against Jahoda's internal criteria for good psychological health. Mixing them up loses the distinction examiners are testing.

4. Naming fewer than the six Jahoda criteria

A question worth several marks expects the full set: positive self-attitudes, self-actualisation, autonomy, resistance to stress, accurate perception of reality, and environmental mastery. Listing only three or four leaves marks on the table.

5. Treating one definition as the single "correct" answer

There is no single best definition. Each captures part of the picture and each has weaknesses, so evaluation questions reward showing how they compare — not defending one and dismissing the rest.