1. The Relationship Between Participant & Investigator Many investigations create a social situation involving both researcher and participant Many investigations create a social situation involving both researcher and participant This relationship can affect the outcome of the study, threatening validity This relationship can affect the outcome of the study, threatening validity Investigator effects Investigator effects Demand characteristics Demand characteristics psychlotron.org.uk

2. Types of Investigator Effect Experimenter behaviour effects Experimenter behaviour effects Experimenters react to PPs as people (and PPs react to experimenters) Experimenters react to PPs as people (and PPs react to experimenters) Behaviour of experimenter may affect attitude of PPs towards the task Behaviour of experimenter may affect attitude of PPs towards the task E.g. conveying dislike for some PPs, conveying impression that a task is difficult etc. may affect motivation E.g. conveying dislike for some PPs, conveying impression that a task is difficult etc. may affect motivation psychlotron.org.uk

3. Types of Investigator Effect Expectancy effects Expectancy effects The investigator has an idea of what outcome to expect in a study The investigator has an idea of what outcome to expect in a study (1) They may be biased in the observations they make, being more disposed to see things that are in line with expectations (1) They may be biased in the observations they make, being more disposed to see things that are in line with expectations (2) They may communicate their expectations to the PPs (2) They may communicate their expectations to the PPs psychlotron.org.uk

4. Types of Investigator Effect Demand characteristics Demand characteristics Cues that the participants use to work out the experimental aim Cues that the participants use to work out the experimental aim They may alter their behaviour as a result either: They may alter their behaviour as a result either: (1) in line with expectation (pleasing the experimenter) (1) in line with expectation (pleasing the experimenter) (2) away from expectation (’screw you’; Masling, 1966) (2) away from expectation (’screw you’; Masling, 1966) psychlotron.org.uk

5. Sources of Demand Characteristics Poor research design decisions Poor research design decisions E.g. exposing pps to knowledge of both conditions when it’s important they don’t know what the IV is E.g. exposing pps to knowledge of both conditions when it’s important they don’t know what the IV is Researcher behaviour/expectancy Researcher behaviour/expectancy E.g. unintentional reinforcement of desired responses E.g. unintentional reinforcement of desired responses psychlotron.org.uk

6. Dealing with Issues Pilot the procedure Pilot the procedure Get feedback from pilot pps Get feedback from pilot pps Did they understand everything? Did they understand everything? Did they realise what the aim was? Did they realise what the aim was? Did they pick up on any particular aspects of the researcher’s behaviour? Did they pick up on any particular aspects of the researcher’s behaviour? psychlotron.org.uk

7. Dealing with Issues Standardise everything Standardise everything I.e. ensure it is exactly the same for all the PPs I.e. ensure it is exactly the same for all the PPs Instructions given Instructions given Procedures followed Procedures followed psychlotron.org.uk

8. Dealing with Issues Single blind procedure (standard) Single blind procedure (standard) Prevent pps from finding out what the aim is Prevent pps from finding out what the aim is Problem: can never be sure the researcher won’t give cues Problem: can never be sure the researcher won’t give cues Double blind procedure Double blind procedure Prevent pps from being cued at all by employing a researcher to carry out the procedures who does not know the aim of the research Prevent pps from being cued at all by employing a researcher to carry out the procedures who does not know the aim of the research psychlotron.org.uk