Passive consent. Participants are informed of the study, and are considered to agree to participate unless they specifically decline to be included in the study. This procedure is often used in schools that send forms to parents asking them to allow their students to participate in various studies or activities. Although it yields high participation rates, it should be limited to completely innocuous research (typically not involving minors). It is acceptable for participant observation (ethnographic) projects.
Implied consent. Participation in the study is proof of consent. This is acceptable for studies that provide anonymity, such as opinion surveys. A statement at the top of the instrument should clearly state that by filling it, the participant consents to participate, but does not wave any of their rights as research participant. Projects using implied consent should use the consent statementtemplate provided in this website, or a similar document, in their proposal. It provides active implied consent.
Some participants, although not legally competent, are able to make judgment about their participation themselves. This is the case for teenagers and some mentally impaired individuals, for instance. The assent formgives them an opportunity to express their agreement to participate in research in writing, beyond the consent given by a legal guardian or parent. Although the assent is not legally binding, and does not dispense a researcher from obtaining consent from a parent or legal guardian, it is advisable as sound ethical practice. It reinforces the voluntary nature of participation.
Active consent. Participants indicate their willingness to participate by agreeing to a specific statement, and then are included in the study. This is the most common, and recommended, form of consent for research.