Variables and the Experimental Method

Number of words recalled Independent Variable Caffeine influences Dependent Variable Number of words recalled Time of day 2 Conditions Tea/ Coffee Extraneous Variables Noise

Number of words recalled Independent Variable Caffeine influences Dependent Variable Number of words recalled Time of day Confounding Variable Tea/ Coffee Extraneous Variables Noise

Psychologists try to control extraneous variables so that they don’t become confounding variables. This means experiments can show cause and effect.

No caffeine drinks for 12 hours previously Quiet environment used Independent Variable Caffeine influences Dependent Variable Number of words recalled Time of day All tested at 9 am No caffeine drinks for 12 hours previously These are controls Tea/ Coffee Quiet environment used Noise

There are 3 types of variables to control Controls There are 3 types of variables to control

Participant Variables Situational Variables Experimenter Variables Time of day Heat Participant reactivity Body language Tone of voice Age Intelligence Personality Order Effects Demand Characteristics Bias

Participant Variables

Individual Differences Age, gender, mood, background, ethnicity, IQ, personality, memory, beliefs, past experiences………….

Controls for Individual Differences Allocation Sample Randomly allocate to conditions Sample large and randomly to gain representative samples Design Use Repeated Measures or Matched Pairs

Controls for Situational Variables 1. Standardise – keep everything the same for each participant Standardised Procedure Standardised Instructions

Controls for Situational Variables 2. Counterbalance – to reduce effect of situational variables or order effects Split the group in half Group 1 do condition 1 > 2 Group 2 do condition 2 > 1 This “balances” out any order effects. E.g. If you do better on the 2nd test, 50% will do better in Condition 1 and 50% do better in condition 2

Demand Characteristics refers to an experimental artefact where participants form an interpretation of the experiment's purpose and unconsciously change their behaviour accordingly

Controls for Demand Characteristics Deception Single Blind Drug Deception Distractor questions Single Blind Lying about the aim The participant is unaware of which condition they’re in Placebo

Experimenter Variables The experimenter effect is a term used to describe subtle cues or signals from an experimenter that affect the performance of participants in studies. The cues may be unconscious nonverbal cues, such as muscular tension or gestures. They may be vocal cues, such as tone of voice.

Experimenter Variables My beliefs about what I’m studying can create bias. This could be subconsciously (or consciously). This is experimenter bias.

Controls for Experimenter Variables Inter-rater reliability Double Blind Inter-rater reliability Neither the researcher or the participant knows which condition they are in Independent raters rate same behaviour as researcher – check for agreement