Manipulating Variables in Experimental Psychology Research
This paper examines the roles of independent, dependent, extraneous, and confounding variables in experimental research design. Drawing on Weiten's (2013) foundational definitions, it explains how researchers manipulate independent variables to measure their effect on dependent variables, while managing extraneous factors that could distort results. The paper also discusses the importance of operational definitions in ensuring clarity and validity. Schmidt's (1994) study on the effects of humor on sentence memory is used as a concrete example, illustrating how variables are identified, operationalized, and manipulated to produce meaningful findings about how humorous presentation affects word recall.
- Introduction to Variables in Experimental Research: Defines dependent, independent, and variable roles
- Extraneous and Confounding Variables: Explains uncontrolled factors affecting experimental results
- Operational Definitions of Variables: Describes how variables are measured and defined
- Schmidt's Humor and Memory Study: Applies variable concepts to humor-memory experiment
- Findings and Implications: Reports humor's effect on word recall outcomes
✍️ How to write this paper — guide, tools & examples ▾
What makes this paper effective
- The paper moves logically from abstract definitions to a concrete research example, making complex methodology concepts accessible and grounded.
- It uses precise disciplinary vocabulary (dependent, independent, extraneous, confounding, operationalized) consistently and correctly throughout.
- The Schmidt (1994) example is well-chosen — its three-condition design (jingle, joke, control list) clearly maps onto every concept introduced earlier in the paper.
Key academic technique demonstrated
The paper effectively demonstrates concept-to-application scaffolding: each theoretical term is defined first, then immediately illustrated through a real experimental study. This technique is especially useful in methodology writing because it shows that the writer understands not just the label but the functional role each variable type plays in research design.
Structure breakdown
The paper opens with core definitions of dependent and independent variables, then layers in extraneous and confounding variables as complicating factors. It next addresses operational definitions as a methodological requirement. The final two sections apply all prior concepts to Schmidt's (1994) humor-and-memory experiment, describing both the experimental design and the key findings. The references section follows APA format throughout.
Introduction to Variables in Experimental Research
A variable is a factor that can be changed and generally can be measured. A dependent variable is the factor being measured in an experiment — the variable that investigators expect will be changed by the independent variables. Independent variables are those factors that are manipulated or introduced in a study in order to explore how they affect the dependent variable (Weiten, 2013). The independent variable is considered independent because the researcher is free to manipulate, introduce, or remove it over the course of an experiment (Weiten, 2013). Accordingly, the dependent variable is considered to be at least partly dependent on the changes that occur in the independent variable (Weiten, 2013).
Extraneous and Confounding Variables
Extraneous variables may have an impact on the relationship between the dependent variable and the independent variables. Two types of extraneous variables must be considered during an experiment: (1) extraneous variables related to the participants in a research study, and (2) extraneous variables related to the circumstances of the study (Weiten, 2013). In many cases, the researcher is able to control extraneous variables to some degree. However, confounding variables cannot be controlled and have the potential to distort the relationship between the dependent variable and the independent variables (Weiten, 2013).
Operational Definitions of Variables
Operational definitions of independent and dependent variables describe how the variables are measured in a research study and how they are defined within the research. The factor being measured must be operationally described in a manner that adds clarity to both the discussion and the experiment. The instrumentation used to test the attributes of the dependent variable and the independent variable must also be clearly and operationally defined.
Schmidt's Humor and Memory Study
Schmidt (1994) conducted an experiment to explore the effects of humor on memory. Given the research question — What are the effects of humor on memory? — the dependent variable in this study is memory, and the independent variable is humor. Schmidt presented study participants with a list of words to memorize. One third of the words were part of a jingle, one third were part of a joke, and one third were presented only as a disjointed list of terms serving as a control condition.
The words were all evaluated for commensurate difficulty, familiarity, and ease of pronunciation in order to ensure adequate construct validity and content validity. The measure of effect was a frequency count of correctly recalled words under each of the three experimental conditions: jingle, joke, and nonsensical list. The independent variables were, therefore, the presentation of the words in the form of a jingle, a joke, or the control list.
References
Schmidt, S. R. (1994). Effects of humor on sentence memory. Journal of Experimental Psychology: Learning, Memory, and Cognition, 20(4), 953–967.
Weiten, W. (2013). Psychology: Themes and variations (9th ed.). Wadsworth.
Create your account
Always verify citation format against your institution’s current style guide requirements.