Identifying Independent Variables - A Foundational Lesson for A-Level Psychology Students

I, Jyotika Varmani, tutor students of Psychology at all levels. I reside in Mumbai and tutor students online. You can contact me personally on my e-mail id jyotikapsychology@gmail.com or call/message me on 9892507784 for enquiries.

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Year after year, assessments of AS and A psychology papers reveal this one striking issue - students fail to identify the independent variable in novel research stimuli presented to them. Expectedly, this inability is further reflected in their failure to correctly formulate an independent variable in the answer which requires them to design a study of their own. Since the ability to identify the independent variable is so fundamental to the AS and A levels, in the present post, I present you with a detailed but easy, illustrated conceptual understanding of the same; followed by a few exercises for you to sharpen your skills:

What is an independent variable?

Let's begin with what a variable is. A variable is anything that changes from time to time. In other words, it is anything that varies. Contrast it with a constant - a constant is something that never changes, it is always stable.

An example of a variable is your weight. If you step on a weighing scale, you will find yourself to be of at least a slightly different weight on different days or even on different times of the same day. An example of a constant is the weight of your television set. You weigh it today in the afternoon or at night, or tomorrow or a week after - you'll find its weight to be the same. 

Human characteristics are variable - they keep changing, especially human psychological or mental characteristics. Your mood, the amount of stress you experience, your tastes and preferences, your desire for social interaction, your intelligence and everything else related to your mind keeps changing more or less from time to time. 

In the same way, the situations of every human's life are variable - you have days when people appreciate you and days when they belittle your efforts, you have phases in your life when you have a lot of money to spend and phases when you're forced to be tight-fisted, you have days when your health is at its pink and days when pain overwhelms you. Psychologists are interested in both of these - the things that keep changing outside of you and the things that keep changing inside you - because both these kinds of variables influence your mind. The variables inside and around you keep varying your psychological characteristics. In other words, as things change around you and inside you, the way your mind functions also changes.

Coming to what an independent variable is now. As students of psychology, you are well aware that the ultimate goal of any psychologist, no matter which approach she may adopt, is to study the human mind. As we just saw, the human mind keeps changing from time to time in  several respects. Obviously, psychologists are keen to know exactly what brings about these frequent changes in the mind. Think for yourself - what brings about changes in your mind? For instance, what changes your mood? Recalling something? Interacting with someone? Reading the news? As another example, what changes your intelligence? Academic learning? Exposure to challenging situations? Accumulation of general knowledge? No matter what it is, there is some cause behind a change or a variation that takes place on your mind, be it from within you or from the outside. The changes in your mind depend on these external and internal changes.

Sometimes, psychologists simply study the changes in your mind, making scientific assumptions about what the causes behind these changes must be. At other times, they produce the causes that will bring about changes in your mind. Doing so helps them study the changes in your mind systematically. Take for example, a psychologist who  wants to study what causes you to feel anxious. She could conduct a study on you when you were anxious and find out the causes behind your anxiety. Or, she could choose one variable that she believes makes you anxious and make you experience it to see whether her belief is correct. For instance, she could give you a few difficult math problems to solve and see how this influences your anxiety. Taking this approach over the former gives her the ability to control how she exposes you to the math problems at her will - remember, this is possible because what she is controlling is a variable. Accordingly, she could expose you to mildly difficult problems, moderately difficult problems, highly difficult problems and so forth and keep noting the changes in your anxiety levels in response to each of these. As would be obvious to you by now, this approach is very useful to a psychologist for she can study the cause-effect relationship very carefully as she needs to - this would be impossible if the variable was naturally occurring and not under her control. 

*Two points to be noted here - one, the study of cause-effect relationships is called an experiment. Since it is not the focus of  the present lesson I do not discuss the details of the method here but you would be correct in associating independent variables with experiments. Two, you might wonder then, what discovered causes are called in studies that are not experiments. In those cases, causes are referred to as predictor variables or explanatory variables; the main distinction being that independent variables are under the control of the researcher.

The variable that the psychologist keeps changing under her control is the cause of an effect, the effect being the corresponding change in your mental functioning. In the given example, the psychologist has taken charge of the difficulty of the math problems she presents you with and she tests the corresponding changes in your anxiety levels in response to it. The difficulty of the math problems here is therefore, the cause and your anxiety levels are the effect. In psychological terms, the cause assumed behind an effect and controlled by the researcher is called an independent variable. Relate this to what I explained earlier - the changes around and inside you are what psychologists bring about in their studies so that they can study their effects on your mental functioning; and these controlled changes are termed as independent variables in these studies. 

Let's make a quick review of what we've learnt from the above:

• Anything that changes or varies from time to time is called a variable;

• Psychologists study a number of human mental characteristics, all of which are variables - examples being stress, intelligence, anxiety, recall, mood, etc.;

• How these mental characteristics vary is found to depend on conditionss that vary within and around individuals. Such conditions are therefore, assumed to be the causes of changes in mental characteristics;

• These causal conditions, being variable themselves, are referred to as independent variables when they are controlled by a researcher to study their impact on a psychological characteristic.

Finally, let's get a little technical, for we need to develop some terminology for independent variables. Have a good grasp over the following terms -

• Variable - anything that changes from time to time;

• For example, satisfaction, concentration, tolerance, fatigue, etc. are all variables

• Independent variable (IV) - the presumed cause of an effect, a variable controlled by a researcher while investigating a cause-effect relationship;

• For example, difficulty of math problems presented to a participant is an independent variable;

• As another example, the type of drug administered to a participant is an independent variable

• Manipulation of an independent variable - changes brought about in an independent variable by a researcher;

• For example, when a researcher changes the difficulty of math problems she presents a participant with, she manipulates the independent variable -  difficulty of math problems;

• As another example, if a researcher administers a memory drug to one group of participants and a placebo to another group, she manipulates the independent variable - the type of drug administered;

• Levels of an independent variable - the different states in which an independent variable is presented or induced;

• Since the independent variable is a variable, something that can be changed, it is presented in different ways to the same or different individuals. Each different way of presentation is referred to as a level.

• Since the independent variable is a variable, it must exist at at least two levels for otherwise it would be a constant.

• For example, mildly difficult math problems is one level of the independent variable - difficulty of math problems, moderately difficult math problems is another level of the same independent variable and highly difficult math problems is yet another level of the same independent variable;

• As another example, placebo is one level of the independent variable - type of drug administered and memory drug is another level of the same independent variable.

How do you go about identifying independent variables?

When reading through a stimulus in which you need to identify the independent variable, simply ask yourself the following questions, in order:

• Which are the variables in this stimulus? That is, which are the things that are changing or are expected to change here?

• In response to this question, you will obtain at least two answers. Focusing on these, ask yourself the next question-

• Which of these is being  controlled by the researcher?

• Here you will have found your independent variable. Keep in mind though, that the identification of an independent variable is incomplete without identification of its levels. Therefore, move to the next question-

• In which ways has the independent variable been changed by the researcher?

• List all these ways and you will have identified the levels of the independent variable.

*There is one more way of identifying the independent variable - which is by identifying the dependent variable first. Since I have not explained dependent variables in this post, I have not outlined that method.

Solved Practice Exercises

Stimulus - John is planning a study in which he will ask his participants to recall a list of words which he reads out to them once at the rate of one word per minute and once at the rate of two words per minute. He will then compare how many words they remembered after each presentation. 

Q. Identify the independent variable of this experiment.

Let's move through the steps for identification listed earlier:

• The things that are changing and are expected to change in this stimulus are-

• The rate at which the list of words is read out; and

• The recall of participants for the words

• Among these, the rate at which the list of words is read out is being controlled by the researcher. Hence, it is the independent variable.

• This independent variable has been changed in the following ways by the researcher i.e. the rate at which the list of words is read out is either:

• One word per minute; or

• Two words per minute

These are, therefore, the two levels of the independent variable.

Ans. The independent variable in the given stimulus is the rate at which the list of words is read out, manipulated at two levels:

• One word per minute; and

• Two words per minute.

I'll solve one more stimulus which represents a quasi experiment, a design that tends to confuse students with respect to its independent variable.

Stimulus - Mary is studying how individuals suffering from schizophrenia respond to friendly approaches from strangers. She recruits two groups of participants - one suffering from schizophrenia and the other, normally functioning individuals. She then exposes both of them to a stranger who approaches them with a smile.

Q. Identify the independent variable of this experiment.

Let's move through the steps for identification listed earlier:

• The things that keep are changing in this stimulus are-

• The mental functioning of participants; and

• The response of participants to the approaching stranger.

• Among these, type of participants recruited is under the control of the researcher. Hence, it is the independent variable.

• This is key. The researcher does not control the mental functioning of participants. However, she does control her selection of participants in the study - whether they have disturbances in mental functioning or not.

• This independent variable has been changed in the following ways by the researcher i.e. the type of participants recruited by the researcher are either:

• Suffering from schizophrenia; or

• Normally functioning

These are, therefore, the two levels of the independent variable.

Ans. The independent variable in the given stimulus is type of participants recruited, manipulated at two levels:

• Suffering from schizophrenia; or

• Normally functioning

*The problem with these types of questions is that students confuse manipulation of the independent variable with the random assignment of participants. In quasi experiments, the independent variable is manipulated. What is not done is the random assignment of participants to different levels of the independent variable.

Just follow the steps listed for identifying the independent variable and you will not encounter this problem.

Exercises for you to practice:

Q. Identify the independent variable in each of the following stimuli:

1) A researcher divides her participants into two groups - one of which she makes watch a sports match and the other, a romantic drama. She then asks them to complete a questionnaire, responses on which will reveal their mood.

2) A researcher recruits male and female participants for his study. Treating them as separate groups, he asks them to solve a series of decision-making tasks to compare whether males are better decision makers or females.

3) A researcher tests the creativity of his participants by asking them to write an essay, draw a picture and sculpt a model, one after another.

4) A researcher's assistants mock fight on the streets to check whether passerby will intervene in their fight which they would not know is simulated. On one day, they pretend to assault each other physically while on another, they simply quarrel.

5) A researcher tests the endurance of her participants in extremely hot conditions followed by extremely cold conditions. She also tests their stress levels after exposure to each condition.

Are you also interested in knowing how you can construct independent variables? Though it is beyond the scope of the present lesson, I can make a separate post on the same. Let me know if you wish for such a lesson in the comments below.

Do solve the exercises given here and leave your answers in the comments below. I will revert with feedback as soon as possible. Your feedback and suggestions are always welcome.

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