extraneous variables

• participant variables


  refers to any characteristics or traits of participants that might unfairly influence the results - e.g. motivation, opinions, personality, gender, age, race
• investigator effects


  any cues from an investigator (other than IV) that encourage certain behaviours in the participant which might allow researcher's expectations to unfairly influence the results - e.g. body language (smiling, eyebrow raise, head shake), leading questions, tone of voice
• environmental variables


  any aspect of research environment or situation that might unfairly influence the results - e.g. noise, lighting, temperature, location, weather, time of day
• demand characteristics


  any cues that reveal aims of the study to the participants - participants become aware that they're being studied - cues may help them work out what researcher expects to find and cause them to change their behaviour in one of the following ways:

  to try and please the researcher and give the results they want

  try to ruin the experiment and results (screw you effect)

  be more self conscious if they know they're being tested (social desirability)

  results don't reflect real life