4 main causes of extraneous variables- 1. situational factors (things to do with the environment the research is carried out in e.g. temperature, time of day or noise) 2. participant variables (things to do with the participants e.g. ages, gender, IQ, eyesight, hearing, personality) 3. experimenter variables (things to do with the researcher e.g. investigator effects) 4. order effects (practicing or getting bored have an effect on the participants' results)