This document discusses different definitions of abnormality in psychology. It notes that defining something as abnormal implies it is undesirable and in need of change, so the term must be used carefully. Three definitions are presented: statistical infrequency, where a trait is abnormal if it is rare; deviation from social norms, where behavior is abnormal if it violates unwritten social rules; and lack of objectivity, where an abnormal definition should not depend on opinions and should produce consistent results. Context is important for the social norms definition, considering the degree and importance of any norm violations.

1. Definitions of Abnormality Defining a person or behaviour as ‘abnormal’ implies something undesirable and requiring change Therefore, we must be careful how we use the term Psychologists need methods for distinguishing ‘normal’ from ‘abnormal’

2. Definitions of Abnormality Our definition of abnormality must be objective: It must not depend on anyone’s opinion or point of view It should produce the same results whoever applies it It must not be under- or over-inclusive It must not label as ‘abnormal’ or ‘normal’ behaviours or traits that aren’t

3. Statistical Infrequency Under this definition, a person’s trait, thinking or behaviour is classified as abnormal if it is rare or statistically unusual. With this definition it is necessary to be clear about how rare a trait or behaviour needs to be before we class it as abnormal

4. Statistical Infrequency frequency 70 100 130 IQ Scores Average IQ in the population is 100pts. The further from 100 you look, the fewer people you find

5. Statistical Infrequency frequency 70 100 130 IQ Scores A very small subset of the population (<2.2%) have an IQ below 70pts. Such people are statistically rare. We regard them as having abnormally low IQs

6. Deviation from Social Norms Under this definition, a person’s thinking or behaviour is classified as abnormal if it violates the (unwritten) rules about what is expected or acceptable behaviour in a particular social group. Their behaviour may: Be incomprehensible to others Make others feel threatened or uncomfortable

7. Deviation from Social Norms With this definition, it is necessary to consider: The degree to which a norm is violated, the importance of that norm and the value attached by the social group to different sorts of violation. E.g. is the violation rude, eccentric, abnormal or criminal?