Types of Variables (AQA GCSE Psychology)

In psychological research, psychologists are interested in human behaviour and how it is affected and impacted by various factors, called variables

To study the effects of specific variables on behaviour it is necessary to change/manipulate and measure different factors 

The independent variable (IV) is the factor which is changed/manipulated to observe the effect it has on the dependent variable (DV), which is the variable being measured, for example:

• whether participants learn a list of 20 words in silence or the presence of loud rock music (the IV = silence or loud rock music)

• whether participants complete a jigsaw puzzle after 30 minutes of exercise or after no exercise (the IV = 30 minutes of exercise or no exercise)

• whether participants have been exposed to an aggressive adult model or not (the IV = aggressive adult model or no aggressive adult model)

A laboratory experiment must use an IV that has been implemented by the researcher e.g. loud music or silence; the IV cannot be naturally occurring e.g. gender, age, ethnicity

This is the factor which is measured in the study to assess the effect of the IV, for example:

• the number of items recalled from a list of 20

• the time taken in seconds to complete a jigsaw puzzle

• the number of imitative acts of aggression performed in a 20-minute observation schedule

The DV depends on how the IV has been set up:

• If the IV is whether participants learn/memorise something with loud music playing or in silence then it makes sense that the DV is ‘the number of….’ or ‘the time taken to…’ i.e. it must be quantitative 

It is impossible to have a qualitative DV:

• The measure will always take some form of numerical data, which can then be displayed in a graph and analysed

Extraneous variables are any factors that intrude upon and adversely affect the DV (i.e.not the IV, which the researcher has specifically implemented). E.g.

• time of day (some participants may be 'morning people' which means that they are likely to be more alert first thing compared to others)

• temperature (if the experimental space is too warm/cold it may affect participant performance on the task)

• mood (one participant may have just had a row with their partner or won some money or feel a bit ‘off’ that day: any of these events mean that their mood is likely to affect their performance on the task)