Types of Variables in Psychology Research

Imagine you're a researcher studying how sleep affects mood. To explore the connection, you would look at two key "variables": sleep (how much someone gets) and mood (how happy or irritable they feel). In psychology research, variables allow researchers to study certain pieces of information and determine if changes in one lead to changes in another.

Variables in psychology play a critical role in the research process. By systematically changing some variables in an experiment and measuring what happens as a result, researchers can learn more about cause-and-effect relationships.

The two main types of psychological variables are the independent and dependent variables. Both variables are important in collecting data about psychological phenomena.

Dependent and Independent Variables

Two of the most important variables you should learn about are an experiment's independent and dependent variables. Sometimes, these are fairly easy to identify, particularly if the experiment is quite simple. However, this task can become more difficult as the complexity of an experiment increases:

• The independent variable is the variable that is manipulated by the experimenter. An example of an independent variable in psychology: In an experiment on the impact of sleep deprivation on test performance, sleep deprivation would be the independent variable. The experimenters would have some of the study participants be sleep-deprived while others would be fully rested.
• The dependent variable is the variable that is measured by the experimenter. In the previous example, the scores on the test performance measure would be the dependent variable.

So, how do you differentiate between the independent and dependent variables? Start by asking yourself what the experimenter is manipulating.

Intervening Variables in Psychology

In the real world, variables often don't stand alone. In many cases, factors affect the main variables of interest.

Intervening variables, also sometimes called intermediate or mediator variables, are factors that influence the relationship between two other variables. For example, sleep problems in university students are often influenced by factors such as stress.

As a result, stress might be an intervening variable that influences how much sleep people get, which in turn may influence how well they perform on exams.

Extraneous Variables in Psychology

Independent and dependent variables are not the only variables present in many experiments. In some cases, extraneous variables may also play a role.

For example, in our previous example of an experiment on the effects of sleep deprivation on test performance, other factors such as age, gender, and academic background may have an impact on the results. In such cases, the experimenter will note the values of these extraneous variables so any impact can be controlled for.

There are two basic types of extraneous variables:

• Participant variables: These extraneous variables are related to the individual characteristics of each study participant that may impact how they respond. These factors can include background differences, mood, anxiety, intelligence, awareness, and other characteristics that are unique to each person.
• Situational variables: These extraneous variables relate to things in the environment that may impact how each participant responds. For example, if a participant is taking a test in a chilly room, the temperature would be considered an extraneous variable. Some participants may not be affected by the cold, but others might be distracted or annoyed by the room's temperature.

Other extraneous variables include the following:

• Demand characteristics: Clues in the environment that suggest how a participant should behave
• Experimenter effects: When a researcher unintentionally suggests clues for how a participant should behave

Controlled Variables in Psychology

In many cases, extraneous variables are controlled for by the experimenter. A controlled variable is one that is held constant throughout an experiment.

In the case of participant variables, the experiment might select participants that are the same in background and temperament to ensure that these factors don't interfere with the results. Holding these variables constant is important for an experiment because it allows researchers to be sure that all other variables remain the same across all conditions.  

It is important to also note that a controlled variable is not the same thing as a control group. The control group in a study is the group of participants who do not receive the treatment or change in the independent variable.

All other variables between the control group and experimental group are held constant (i.e., they are controlled). The dependent variable being measured is then compared between the control group and experimental group to see what changes occurred because of the treatment.

Confounding Variables in Psychology

If a variable cannot be controlled for, it becomes what is known as a confounding variable. This type of variable can have an impact on the dependent variable, which can make it difficult to determine if the results are due to the influence of the independent variable, the confounding variable, or an interaction of the two.

Operationalizing Variables in Psychology

For example, in our imaginary experiment on the effects of sleep deprivation on test performance, we would need to create very specific operational definitions for our two variables. If our hypothesis is, "Students who are sleep deprived will score significantly lower on a test," then we would have a few different concepts to define:

• Students: First, what do we mean by "students?" In our example, let’s define students as participants enrolled in an introductory university-level psychology course.
• Sleep deprivation: Next, we need to operationally define the "sleep deprivation" variable. In our example, let’s say that sleep deprivation refers to those participants who have had less than five hours of sleep the night before the test.
• Test variable: Finally, we need to create an operational definition for the test variable. For this example, the test variable will be defined as a student’s score on a chapter exam in the introductory psychology course.
  

Once all the variables are operationalized, we're ready to conduct the experiment.

Takeaways

Understanding the different types of variables used in psychology research is important if you want to conduct your own psychology experiments. It is also helpful for people who want to better understand what the results of psychology research really mean and become more informed consumers of psychology information.

While many people understand the basics of the independent and dependent variables, there are also less apparent variables that can affect experimental results. Intervening, extraneous, controlled, and confounding variables are just a few other factors that should be considered when assessing psychology research.