social norms and statistical

Definitions of AbnormalityDefinitions of Abnormality

Defining a person or behaviour as Defining a person or behaviour as ‘abnormal’ implies something undesirable ‘abnormal’ implies something undesirable and requiring changeand requiring change

Therefore, we must be careful how we use Therefore, we must be careful how we use the termthe term

Psychologists need methods for Psychologists need methods for distinguishing ‘normal’ from ‘abnormal’distinguishing ‘normal’ from ‘abnormal’

Definitions of AbnormalityDefinitions of Abnormality

Our definition of abnormality must be Our definition of abnormality must be objective:objective:– It must not depend on anyone’s opinion or It must not depend on anyone’s opinion or

point of viewpoint of view– It should produce the same results whoever It should produce the same results whoever

applies itapplies it

It must not be under- or over-inclusiveIt must not be under- or over-inclusive– It must not label as ‘abnormal’ or ‘normal’ It must not label as ‘abnormal’ or ‘normal’

behaviours or traits that aren’tbehaviours or traits that aren’t

Statistical InfrequencyStatistical Infrequency

Under this definition, a person’s trait, Under this definition, a person’s trait, thinking or behaviour is classified as thinking or behaviour is classified as abnormal if it is rare or statistically abnormal if it is rare or statistically unusual.unusual.

With this definition it is necessary to be With this definition it is necessary to be clear about how rare a trait or behaviour clear about how rare a trait or behaviour needs to be before we class it as needs to be before we class it as abnormalabnormal

Statistical InfrequencyStatistical Infrequencyfr

eque

ncy

70 100 130

IQ Scores

Average IQ in the population is 100pts.

The further from 100 you look, the fewer

people you find

Statistical InfrequencyStatistical Infrequencyfr

eque

ncy

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

Deviation from Social NormsDeviation from Social Norms

Under this definition, a person’s thinking or Under this definition, a person’s thinking or behaviour is classified as abnormal if it behaviour is classified as abnormal if it violates the (unwritten) rules about what is violates the (unwritten) rules about what is expected or acceptable behaviour in a expected or acceptable behaviour in a particular social group.particular social group.

Their behaviour may:Their behaviour may:– Be incomprehensible to othersBe incomprehensible to others– Make others feel threatened or uncomfortableMake others feel threatened or uncomfortable

Deviation from Social NormsDeviation from Social Norms

With this definition, it is necessary to With this definition, it is necessary to consider:consider:– The degree to which a norm is violated, the The degree to which a norm is violated, the

importance of that norm and the value importance of that norm and the value attached by the social group to different sorts attached by the social group to different sorts of violation.of violation.

– E.g. is the violation rude, eccentric, abnormal E.g. is the violation rude, eccentric, abnormal or criminal?or criminal?