Extraneous Variables in Experiments

Lesson in Experimental Psychology

1. Extraneous Variables Prepared by: Orlando A. Pistan, MAEd -GC Psychology Instructor

2. Extraneous Variables One of the goals of a researcher should be to set up experiments that do not create confusion. When experimenting, conditions are created to clearly see the effects of the independent variables. Experiments should be internally validated. Ideally, only the dependent variable should change systematically from one condition to another. Control of the subject variables may lead to worsening.

3. Extraneous Variables There are three types of extraneous variables that may pose problems in experiments. They are: Physical variables; Response style; Response set; Demand characteristics; and Experimenter bias

4. Physical Variables The testing setting, noise, and other distractions are all physical aspects of the testing conditions that need to be controlled. The techniques for controlling physical variables are through: Elimination; Constancy; Screening; and Counter balancing

5. Response Style A subject with a response style has a characteristic way of answering questions. They usually respond “Yes” or “No”; and “True” or “False” to most inquiries.

6. Response Style To contro l this style, experiments should formulate questions in such a way that subjects cannot answer with a simple yes or no. Contents of the inquiry should be built to force the subject to think about their responses.

7. Response Set Subjects with a response set respond in terms of latent content or the meaning behind the questions. Social desirability is the best-known response set. Subjects who have the social desirability response will lie or distort the truth in order to look better in the eyes of the experimenter. Does being gay or lesbian goes against the will of God?

8. Response Set Social desirability can be avoided to some extent by phrasing questions in such a way that alternative answers have roughly the same social value. Does being gay or lesbian goes against the will of God? What is your stand toward being a gay or lesbian?

9. Demand Characteristics The mere fact of being in an experiment can lead to changes in subjects’ behavior which have nothing to do with the experimental manipulations. Their expectation of what will happen to them in the experiment can shape their responses. Subjects may want to be “good” subjects; they may try to provide data that confirm the hypothesis.

10. Demand Characteristics A way of controlling demand characteristics is to run a blind experiment in which the experimenter will tell everything about the experiment except what the researcher expect to find. This is commonly applicable for experiments involving nutrition and drugs.

11. Experimenter Bias The last potential source of error is the experimenter. They may provide subtle cues that tell the subjects how they are expected to behave during the experiment. Example: The experimenter smiles at every time the subject give the desired and predicted response.

12. Experimenter Bias To control experimenter bias, the experimenter must not know how subjects are expected to behave. This approach enables the experimenter to measure the dependent variable more objectively.

13. Extraneous Variables Thank you for paying attention.