PSY2 – Research Methods: Lesson 08

Extraneous Variables

PSY2 RM PowerpointTeachers or students who want the original PPT please tweet @psychopepper

Learning Objectives

  • To KNOW and UNDERSTAND what the definition of an extraneous variable is.
  • To KNOW and UNDERSTAND what participants and situational variables are.
  • To ANALYSE ways in which participants can effect a study and to KNOW and UNDERSTAND what these terms all mean and how they are subtly different from one another.

Lesson Outline:


  1. Complete the MBTI and have your four letter personality code.
  2. Take notes on the definition of extraneous variables in booklet.
  3. Take notes on the definitions of participant and situational variables in booklet and come up with possible examples for each.
  4. Take notes on the participant effects in booklet of participant reactivity, evaluation apprehension, Hawthorne effect, social desirability bias and demand characteristics and reflect on where these were shown during completion of the MBTI.
  5. Create a children’s tab-book on “How participants can mess up experiments” you can make it notes, or a story but the key is to keep the wording simple but get across how they are all subtly different.

Content Recap:

Extraneous Variables: Extraneous variables are nuisance variables which can bias the research and do not vary systematically with the IV. They are things which we are (largely) able to identify before we conduct our experiment and put measures in place to reduce or eliminate. If not they can seriously impact the internal validity of a study. They can confound the results because the change in the dependant variable (DV) may be due to the extraneous variables rather than the independent variable (IV).

Participant Variables: Anything to do with the people used in the study which could effect the DV other than the IV e.g. gender, IQ, ethnicity or personality.

Situational Variables: Anything to do with the environment the study was conducted in which could effect the DV other than the IV e.g. time of day, noise.

Participant Reactivity: Responses and/or behaviours of participants are affected by their awareness that they are part of a study (general term). Or in other words our participants will react to us.

Evaluation Apprehension: Participants are affected by a worry they are being evaluated (judged). They worry about what the outcome means and so second guess answers. For example you were worried about what you four letters in the MBTI meant about you, and asked it yours was ‘good’.

Social Desirability Bias: Participants change their answers to keep in line with social norms. For example people are not willing to admit to having views that are different to mainstream culture.

The Hawthorne Effect: Participants are effected by an awareness they are being observed (OFSTED). Even if they try to ‘act normal’ they cant.

Demand Characteristics: These are CUES which give away the aim of the investigation. They allow the PARTICIPANTS to guess what is expected of them and this can lead to them CHANGE their behaviour. This can have an UNEXPECTED effect which can influence the OUTCOME of the research findings. Demand characteristics come from the INVESTIGATOR, the research SITUATION, the PROCEDURE or the MATERIALS used.

If you would like to access PsychoPepper’s Glossary of Terms please click here

Resources used

Study Notes (TBC):

If you would like to download a set of study notes for this lesson, you can do so here. If you would like access to the original word file please tweet @psychopepper


I would suggest that you have a copy of one of the textbooks which will allow you to read around the subject matter, pre-read ahead of lessons or even take extra notes/practise questions afterwards. I would recommend the following (you do not need to replicate books, one of each type is plenty!)

Extra ReadingElephants on Acid or Hippo Eats Dwarf

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