Defining psychological abnormality has proven to be difficult to psychologists this is due to different cultures and changes over the years. Psychologist over the years have attempted to define psychological abnormality creating four key ways of establishing the difference between normal and abnormal behaviour. They are statistical infrequency, deviation from social norms, deviations from ideal mental health and failure to function adequately.
Failure to function adequately is the definition which is considered when a person is unable to cope with day to day activities and the demands of everyday life, for example, a person who is experiencing this may be unable to keep a job or even interacting with others meaningfully may be difficult. In 1989 Rosenhan suggested there are characteristics that define failure to function adequately which are the following; Suffering, maladapativness, irrationality, unpredictability and loss of control, observer discomfort and violation of standards.
Statistical infrequency in this definition is the method of classification using deviation from an average numerical form showing abnormality within individuals. However, there are limits within this definition due to numerical factors. Abnormality cannot be measured in Statistical infrequency, barely the characteristic that shares the general understanding of abnormality meaning the behaviour must already be seen to be abnormal. The determination whether an individual is really suffering from a psychological abnormality, this definition must be further analysed by a professional.
Deviation from social norms is the definition that is reliant behaviour which is set to moral standards of a specific culture. The law can be part of these rules for example not vandalising and not stealing or can be conventional of specific cultures (e.g. in some African countries eating food is completed by hands rather than a fork and knife. There are boundaries and if a person goes out of those boundaries of these social norms by not following them they are deemed abnormal according to deviations from Social norms. An example of this may be to a sufferer from schizophrenia they may show emotions that are inappropriate emotions such as not show sadness or laugh when announced bad news.
Finally deviation from ideal mental health its method acts as a good definition of standardising what normal is. However, there is a bias and cultural relativism still subject as the previous definitions (deviation from social norms and statistical infrequency) The six criteria suggested it has been shown to be difficult to indicate ideal mental health, however, through other assessments psychologist know that no everyone is abnormal psychologically.