7.2.5

Demand Characteristics & Investigator Effects

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Investigator Effects

Researcher bias is the risk that an experimenter might affect the results of the study. Researcher bias and the placebo effect can be accounted for using double-blind trials.

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Researcher bias/investigator effects

  • This occurs when the researcher in some way influences the outcome of the research. This may occur because of something they say or do (body language) or it may be a result of their own expectations.
    • For example, if they are investigating aggressive behaviour in boys and girls and expect boys to be more aggressive, they are more likely to notice and record examples of aggressive behaviour in boys than girls. In an interview, if the interviewer appears disinterested then the interviewee may change their responses.
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Single- vs double-blind studies

  • In a single-blind study, one of the groups (participants) are unaware as to which group they are in (experiment or control group) while the researcher who developed the experiment knows which participants are in each group.
  • In a double-blind study, both the researchers and the participants are blind to group assignments.
    • This is useful because by doing so, we can control for both experimenter and participant expectations.
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The placebo effect

  • The placebo effect happens when people's expectations or beliefs influence or determine their experience in a given situation.
  • In other words, simply expecting something to happen can actually make it happen.
  • The placebo effect is commonly described in terms of testing the effectiveness of a new medication.
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The placebo effect - depression drugs

  • In the case of testing a drug for depression, for example, a participant taking a pill that they expect will improve their mood might feel better simply because they took the pill and not because of any drug actually contained in the pill - this is the placebo effect.
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Controlling for the placebo effect

  • To control for the placebo effect, one group will receive the real drug and one group will receive a sugar pill and neither the participant nor the experimenter will know which pill they took.
  • The improvements can then be tested between the groups and the control group with the placebo effect can be treated as a baseline.

Demand Characteristics and Social Desirability

Demand characteristics occur when the participant guesses the aim of the research or realises they are being observed and changes their behaviour accordingly.

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Demand characteristics example

  • Participants may try to conform to what they think the researcher wants or they may try to do the opposite.
  • In Milgram’s (1963) research, if participants had known the true aim demand characteristics it would have likely confounded the results, as participants would have been unlikely to obey. This is sometimes known as the hawthorne effect after a study at the Hawthorne Electrical Plant where workers’ productivity increased just because they were aware of being observed.
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Social desirability

  • Social desirability occurs when the participant changes their behaviour or answers in order to look good.
    • E.g. if a teacher asks a student how much they revised over the weekend they will give what they think is a socially acceptable answer and portrays them in the best possible light.
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Controlling factors

  • Both demand characteristics and social desirability bias can be controlled by using a single-blind technique where the participant is unaware of the true aim of the research, but this can lead to ethical issues as it involves deception.

Jump to other topics

1Social Influence

2Memory

3Attachment

4Psychopathology

5Approaches in Psychology

6Biopsychology

7Research Methods

8Issues & Debates in Psychology (A2 only)

9Option 1: Relationships (A2 only)

10Option 1: Gender (A2 only)

11Option 1: Cognition & Development (A2 only)

12Option 2: Schizophrenia (A2 only)

13Option 2: Eating Behaviour (A2 only)

14Option 2: Stress (A2 only)

15Option 3: Aggression (A2 only)

16Option 3: Forensic Psychology (A2 only)

17Option 3: Addiction (A2 only)

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