controlling variables

Question 1

Intro

Answer 1

Crucial concepts in designing experiments that play a key role in determining the validity of psychological research.

• Extraneous variables
• Confounding variables
• Demand characteristics
• Investigator effects
• Randomisation
• Standardisation
• Single/Double blinds

Question 2

extraneous variables

Answer 2

• Variables that are not the independent variable (IV) but could potentially affect the dependent variable (DV).
• Introduce noise into the data, making it harder to determine whether the changes in the DV are truly caused by the IV.
• Researchers must control these variables as much as possible to ensure the results are valid.

Imagine you’re conducting an experiment to test the effect of sleep on memory.
IV: Hours of sleep
DV: Performance on a memory test
EV: Time of day, lighting, noise, temperature

• Extraneous variables do not vary systematically with the IV
• They also don’t necessarily affect all participants equally.
• But if they are not controlled, they could obscure the relationship between the IV and DV.

Question 3

confounding variables

Answer 3

A confounding variable is a specific type of extraneous variable that influences both the independent variable (IV) and the dependent variable (DV) in a way that makes it unclear which one is causing the effect on the DV.
• Vary systematically with the IV.

When studying the impact of exercise (IV) on mood (DV), a confounding variable might be participants’ diet.
• Diet could influence both how much exercise someone engages in and their mood
• Makes it unclear whether exercise or diet is responsible for changes in mood.

Question 4

demand characteristics

Answer 4

• Cues in the experimental environment that may reveal the purpose of the experiment.
• Participants may change their behaviour, either to act in a way they think is expected (to help the
experimenter), or they may deliberately underperform to sabotage the results of the study.

For example, if participants in a study on generosity realize the aim of the experiment is to observe their helping behaviour, they might act more generously than they normally would.

• This means that participants may not be acting naturally during the experiment.
• Reduction of validity of findings.
• Behaviour is not a true reflection.

Question 5

investigator effects

Answer 5

Any unwanted influence of the investigator on the research outcome.
• Interactions with participants
• Actions related to the study’s design
• Selection of participant
• Materials used
• Instructions given, e.g. leading questions
→ Introduces bias and obscures the role of the IV.

A subtle smile from the researcher when an answer is given could give the impression that the response was
“correct” or desirable.-could encourage specific responses

Question 6

randomisation

Answer 6

The use of chance to control for the effects of bias when designing materials and deciding the order of experimental conditions.
• Presenting materials (e.g. words to be memorised) in a random order.
• When participants are involved in more than one condition, the order of the conditions should be randomly determined.
→ Reduction of investigator bias.

Question 7

standardisation

Answer 7

Using the same formalised procedures and instructions and materials for all participants in a research study.
→ Controlling extraneous variables

In a study on memory, if one group is tested in a quiet room and another group in a noisy room, that could affect the results.

Question 8

single blind procedure

Answer 8

When the participant is unaware of details of the experiment, e.g. the aim or the condition they have been allocated to.
Attempts to control for effects of demand characteristics.

Question 9

double blind procedure

Answer 9

Neither the participants nor the researcher who conducts the study are aware of the aims of the investigation.
Attempts to control for the effects of demand characteristics and investigator effects.