Definitions of Abnormal Behaviour:Statistical Infrequency and Deviation from

Social Norms

Specification: Describe the statistical infrequency and the ‘social

norms’ definition of abnormality.Evaluate these definitions in terms of their suitability as

definitions of abnormality.

Home Learning For lesson 1

Definitions of abnormal behaviour

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

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

• However, psychologists do need methods for distinguishing ‘abnormal’ where a person potentially requires some form of intervention, from ‘normal’

4 ways of defining dysfunctional behaviour

• 1) Deviation from social norms• 2) Statistical Infrequency• 3) Failure to function• 4) deviation from ideal mental health

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

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70 100 130

IQ Scores

Mean IQ in the population is 100pts. The further from 100

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Statistical Infrequencyfr

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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

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Two Standard deviations

One Standard deviation

SUMMARY: Statistical Infrequency:• Requires a behaviour/trait to be quantifiable• Requires a behaviour/trait to be normally

distributed within the population- bell curve on a graph.

• The mean for the behaviour/trait can be calculated along with standard deviations away from this point

• Abnormal behaviours/traits are those which fall into the top and bottom 2.5%: typically more than 2 standard deviations away from the mean.

Deviation from Social Norms• Every society has accepted standards of

behaviour, these are sometimes written as part of the law.

• Others are implicit : they are generally accepted but not legally binding• E.g. not standing too close to someone

when they are talking.• Social norms allow for the regulation of

normal behaviour.• One approach to defining abnormal

behaviour is to consider deviations from the social norm as an indicator of dysfunctional behaviour.

Deviation from Social Norms• Examples of social norms include

1. Being polite2. Opening doors for people3. Not hearing voices 4. Not washing your hands 50 times a day5. Queuing in shops6. Not standing too close to people when talking7. Wear clothes when walking around outside

• These are just a few example. If someone was not acting within these social norms, their behaviour would be defined as abnormal.