Types of Variables (AQA GCSE Psychology): Revision Note

Psychologists study how behaviour is affected by different factors, called variables

To study these effects, one variable is changed while another is measured

The independent variable (IV) is the factor the researcher changes/manipulates to observe its effect on the dependent variable (DV), for example:

• whether participants learn a list of 20 words in silence or with loud rock music playing (IV = whether music is playing or not)

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

• whether participants observe an aggressive adult model or not (IV = aggressive model or no model)

Each version of the IV is a condition, and one often acts as the control condition for comparison (silence, no exercise, no model)

In a laboratory experiment the IV must be manipulated by the researcher

Where the IV is naturally occurring and cannot be manipulated (e.g. gender, age, or an event such as a school closing), the study is a natural experiment instead

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 must follow from the IV

• If the IV is music vs silence, the DV is 'the number of words recalled', not just 'memory'

In an experiment the DV must be measurable, so it is always recorded as quantitative (numerical) data, e.g:

• the number of…

• the time taken to…

• the score on…'

An extraneous variable is any variable other than the IV that could affect the DV

• If it is not controlled, the researcher cannot be sure the IV caused the change in the DV

Extraneous variables should be identified and kept constant across conditions, for example:

• time of day ('morning people' are more alert early on)

• temperature (a room that's too warm or cold affects performance)

• mood (a participant who has just had a row, or won some money, may perform differently)