When the researcher's sex affects the behaviour of a participant in a study, it refers to

When the researcher's sex shapes a participant's behaviour, the influence is a biosocial effect.

Biosocial effects flow from observable biological traits of the researcher such as sex, age and race.

Psychosocial effect instead arises from the researcher's attitudes and expectations, not physical traits.

Psychological effect is too broad a label and does not name this specific researcher-trait source.

Environmental effect refers to the setting or surroundings, not to a feature of the researcher.

Both biosocial and psychosocial effects are recognised experimenter-related sources of bias.