Statistical infrequency

The statistical infrequency approach defines abnormal behaviour as one that is uncommon or rare in society. This method evaluates abnormality by examining the distribution of a specific behaviour within the population. For instance, the average IQ in society is roughly 100, with 65% of the population having an IQ between 85 and 115. In addition, around 95% of the population falls within the IQ range of 70 to 130. However, a small minority, approximately 5% of the people, possesses an IQ below 70 or above 130, and as a result, these individuals are classified as abnormal by this definition.

The distribution of a specific characteristic among the population can be depicted through a normal distribution curve. As shown in the figure below, the IQ distribution curve demonstrates that 2.2% of the population has an IQ below 70, and another 2.2% has an IQ above 130. Such individuals are considered statistically rare, and therefore, they are classified as abnormal.

EVALUATING STATISTICAL INFREQUENCY

MISDIAGNOSIS: The statistical infrequency definition of abnormality is not without limitations, as it can lead to misdiagnosis. Some behaviours are statistically common, such as depression, which affects around 10% of the population at some point, and is therefore considered normal according to this definition. Conversely, desirable behaviours like high IQ are statistically uncommon, and thus classified as abnormal despite being advantageous. This drawback highlights the need to exercise caution when using the statistical infrequency approach as a sole criterion for diagnosis. Other factors should be considered in conjunction with this approach to avoid incorrect diagnoses.

LABELLING: Another issue with the statistical infrequency approach to defining abnormality is that labelling an individual as abnormal can be counterproductive. This is particularly applicable, for instance, to individuals with low IQ, who can lead a contented life without causing any harm to themselves or others. Such a label may negatively affect their self-esteem or invite discriminatory behaviour. Therefore, being labelled as statistically uncommon could cause more distress to the person than the condition itself.

DESIRABLE BEHAVIOURS: The statistical infrequency approach may label some behaviours as abnormal that are actually desirable. For instance, possessing a very high IQ is rare, but it can be a highly celebrated trait. In contrast, depression is a prevalent but unwanted experience in many people's lives. Therefore, to avoid such confusion, the statistical infrequency definition of abnormality must distinguish between infrequent and undesirable behaviours. By doing so, this approach can correctly identify abnormal behaviours while avoiding mislabelling of desirable traits.