Scientific processes: Demand characteristics and investigator effects.

The idea

Participants are not passive. Cues in a study, from the consent form to the task itself, let them guess what is expected and act on the guess; these cues are demand characteristics. Some help by producing the result they think is wanted, others deliberately do the opposite. Orne showed participants working at pointless tasks simply because the setting demanded it. The researcher creates investigator effects through leading questions, tone, appearance and expectancy effects, changing the DV without the IV moving. A single blind hides the condition and aim from the participant to reduce demand characteristics, while a double blind hides them from the researcher too.

What earns the marks

• Defines the participant effect as cues that reveal the aim, leading to a change in behaviour.
• Distinguishes those who try to please the researcher from those who deliberately underperform.
• Defines the researcher effect as any influence of the investigator, other than the IV, on the DV.
• Gives examples such as leading questions, tone of voice, appearance or expectancy effects.
• Names controls: single blind, double blind, standardised instructions and a cover story, and links them to internal validity.

Common mistakes and how to put them right

• Treating the two terms as interchangeable, when one comes from the participant and one from the researcher.

• Saying participants 'try harder' without explaining that this changes the DV independently of the IV.

• Describing a double blind as the participant not knowing, which is a single blind.

• Claiming deception always removes the problem, ignoring that the setting itself still carries cues.

Exam tips

• Pin the effect to the DV: explicitly state that scores change for a reason other than the IV, which compromises internal validity.
• Use the scenario's own cue, for example the researcher watching and taking notes, rather than an abstract definition.
• When suggesting a control, say who is kept ignorant of what, because that detail distinguishes single from double blind.