In a study, when the age, sex or race of the researcher affects the behaviour of the participant, it is called:

When a researcher's age, sex or race changes how a participant behaves, it is called a biosocial effect.

Biosocial effects arise from the visible biological and social traits of the experimenter influencing responses.

The psychosocial effect refers to broader mental and social factors, not specifically the researcher's own attributes.

The Hawthorne effect is when people change behaviour simply because they know they are being observed.

Evaluation apprehension is anxiety about being judged, which can distort performance in a study.

Such experimenter effects are a threat to the validity of behavioural research.