Psychological variables refer to elements in psychological experiments that can be changed, such as available information or the time taken to perform a given task. Variables can be classified as either dependent or independent. Researchers investigate the possible effect on the dependent variable that may arise due to change in the independent variable.
Generally, variables are applied in psychological experiments to determine if changes to one element cause changes to another. The dependent variable is the variable that the researcher measures upon alteration of the independent variable. The independent variable is a variable that the experimenter manipulates with the expectation of having an effect on the dependent variable. For instance, in a study on the impact of sleep deprivation on test performance, sleep deprivation is the independent variable, while the scores on the test performance make up the dependent variable. An experimenter may also change the type of information, whether organized or random, given to participants to determine the effect on the amount of information remembered. In this case, the type of information is the independent variable (because it changes), and the amount of information remembered is the dependent variable (because it is what is being measured).
Psychological variables may also be categorized as extraneous variables, which have an impact on the relationship between the independent and dependent variables. For instance, when investigating the effects of sleep deprivation on test performance, factors such as age, gender and academic background may have a significant effect on the results.