Definitions of Abnormality
One of the most fundamental questions in psychopathology is: how do we define "abnormal" behaviour? There is no single, universally accepted definition of abnormality. Instead, psychologists use several different approaches, each with its own strengths and limitations. Understanding these definitions and being able to evaluate them critically is a core requirement of AQA A-Level Psychology.
Key Definition: Abnormality in psychology refers to behaviour, thoughts, or feelings that deviate from what is considered normal, acceptable, or healthy. Different definitions emphasise different criteria, and no single definition is sufficient on its own.
1. Statistical Infrequency
The statistical infrequency definition identifies abnormality as behaviour that is statistically rare — that is, behaviour that falls outside the range of what is typical for the population. Any behaviour that deviates significantly from the statistical average is considered abnormal.
How It Works
In many psychological characteristics (e.g., IQ, anxiety levels), scores follow a normal distribution (bell curve). Most people cluster around the mean, and scores become increasingly rare as they move further from the average. Abnormality is defined as scores that fall in the extreme tails of the distribution — typically more than two standard deviations from the mean.
Example: IQ Scores
| Range | Classification | % of Population |
|---|
| Below 70 | Intellectually disabled (abnormally low) | ~2.27% |
| 70–85 | Below average | ~13.59% |
| 85–115 | Average (normal) | ~68.27% |
| 115–130 | Above average | ~13.59% |
| Above 130 | Gifted (abnormally high) | ~2.27% |
Under this definition, an IQ below 70 would be considered "abnormal" because it occurs in fewer than 2.5% of the population. This criterion is actually used in the clinical diagnosis of intellectual disability.
Evaluation of Statistical Infrequency
Strengths:
- The definition is objective and quantitative — it uses numerical data to define abnormality, avoiding subjective judgements.
- Some mental health diagnoses do use statistical criteria — for example, intellectual disability is diagnosed partly based on an IQ below 70, and clinical thresholds for anxiety or depression are based on scores above certain cut-off points on standardised assessments.
- It provides a clear cut-off point, which can be useful for clinical decision-making.
Limitations:
- Not all statistically rare behaviour is abnormal in a negative sense. A person with an IQ of 150 is statistically unusual, but we would not consider them psychologically abnormal. Similarly, exceptional happiness, creativity, or athletic ability are statistically rare but desirable.
- Not all abnormal behaviour is statistically rare. Depression is very common (affecting approximately 1 in 4 people at some point), yet it is clearly abnormal in the clinical sense. If we relied solely on statistical frequency, depression might not be classified as abnormal.
- The cut-off point is arbitrary. Why is an IQ of 69 "abnormal" but an IQ of 71 "normal"? The line between normal and abnormal is not a natural boundary but a decision made by clinicians.
- Cultural differences are not accounted for. Behaviours that are common in one culture may be rare in another. Statistical norms depend on the population being studied.
Exam Tip: When evaluating statistical infrequency, always give specific examples of its limitations — such as high IQ being rare but desirable, or depression being common but abnormal. Generic statements without examples will not gain full marks.
2. Deviation from Social Norms
This definition identifies abnormality as behaviour that violates the unwritten rules of a society. Every society has expectations about acceptable behaviour — social norms — and behaviour that deviates from these norms may be considered abnormal.
How It Works
Social norms are the implicit and explicit rules that govern behaviour within a culture. They include standards of politeness, dress, personal space, emotional expression, and social interaction. Behaviour that significantly violates these norms — especially behaviour that causes discomfort or distress to others — may be classified as abnormal.
Examples:
- Hearing voices (auditory hallucinations) is considered abnormal in most Western societies because it violates the social norm that people should perceive reality accurately.
- Extreme antisocial behaviour, such as unprovoked aggression, violates norms of social cooperation.
- Some symptoms of schizophrenia, such as thought disorder or bizarre delusions, clearly deviate from expected social behaviour.
Evaluation of Deviation from Social Norms
Strengths:
- The definition considers the social context of behaviour, recognising that behaviour cannot be judged in isolation from the society in which it occurs.
- It accounts for behaviours that are clearly problematic even if they are not statistically rare (e.g., antisocial personality disorder).
- It captures the idea that abnormality involves a failure to conform to expected standards, which is often a key feature of mental disorder.
Limitations:
- Social norms vary across cultures and over time (cultural relativism). Homosexuality was classified as a mental disorder by the American Psychiatric Association until 1973. In some cultures, hearing voices is considered a spiritual gift, not a symptom of mental illness. Using social norms to define abnormality risks labelling culturally different behaviour as abnormal.
- Social norms can be used to control non-conformity. Throughout history, political dissidents, minorities, and unconventional individuals have been labelled as "mentally ill" as a means of social control. Szasz (1960) argued that the concept of mental illness is a "myth" used to control people who deviate from social norms.
- Not all social norm violations indicate mental disorder. Criminal behaviour, eccentricity, and nonconformity all violate social norms but are not necessarily signs of psychological abnormality.
- The definition is subjective — different people within the same society may disagree about what constitutes a norm violation.
Key Definition: Cultural relativism is the principle that behaviour can only be judged as normal or abnormal within the context of the culture in which it occurs. What is normal in one culture may be abnormal in another.
3. Failure to Function Adequately