Response is influenced because you're being observed
Participants changing during process of experiment
A difference (sex, major, etc.) in the groups of people.
Something going on between the subjects.
Eg. Students in 10a class telling students in 11a class about test.
Group deprived on stimulus will work harder because they know they have to over come something.
Opposite of compensatory rivalry, they just give up and don't try to do better.
Involves a researcher or a confederate who is aware of the study's purpose, variables and hypotheses, this individual could unconsciously threat participants differently in the carious conditions of the study.
The researchers' knowledge of the research study's purpose, variables and hypotheses biases their observations of the dependent variable in some way.
Researcher attribute effect
When some characteristic or feature of the researcher systematically affects the participant responses in a study.