According to critiques of traditional qualitative research, the fact that research subjects do not actively participate in a study weakens both the findings in themselves and their legitimacy. Especially when studies focus on traditionally marginalized groups, such as rural communities, minorities and the physically disabled, the application of external research methodologies to a community that does not necessarily understand the study or its methods represents an imposition of power over the community, using disadvantaged research subjects to produce knowledge that is neither understandable nor relevant to the community in question. In response, participatory research methods propose a system where the groups studied participate directly in the construction of the research design, actively contribute to the creation of findings and help in the shaping of conclusions.
The field of human service research -- including studies such as the effectiveness of potable water systems or health services -- has generated many of the most recognized participatory research methods. In a participatory evaluation of a city sewer system, for example, researchers would begin by asking research participants, members of the group that uses the service, to explain how they would evaluate the effectiveness of the system themselves. In contact with researchers, the participants outline their priorities for the system and what they perceive as its greatest weaknesses, allowing researchers to better understand how the community experiences the system and what factors determine the success of the system for its users. Data is then collected from the participants through whatever collection method the researcher uses and explains to participants. The findings are shared with the community in a way that the community of participants can understand.
Naturally, participatory methods allow a researcher to better understand the situation he is studying, an obvious benefit for the quality and legitimacy of results. In the case of the sewer system evaluation, participation allows a researcher to document how users actually make use of the system, generating evaluations that anticipate the needs of users rather than the use of criteria drawn from other examples that may or may not be applicable. If, for instance, the users refrain from using running water during a certain period of each day for cultural reasons, the system's response to peak usage may be more important than average daily flows, a fact that would be missed by a researcher that did not actively seek community participation. Participatory research also allows a researcher to incorporate local evaluation methods as a better guideline for the system's improvement and a more understandable metric for study participants.
Just as the benefits of participatory research depend mostly on the high level of specificity of the research design to the particular case studied, that level of local sensitivity also presents a structural disadvantage. While science traditionally developed based on the ability to compare different results and studies to the same set of theories, the high level of variation in research designs created by a method that always takes participant concerns into account when constructing a study makes different research projects more difficult to compare against each other. In general, this makes the process of drawing global conclusions far more difficult.
Proponents of participatory research methods sometimes go one step further in proposing methodological change in the social sciences, advancing a branch of participatory research known as emancipatory research. Like other forms of participatory research, emancipatory research begins by taking participant concerns into account when designing and conducting a study, yet emancipatory research methods also aspire to make the research method reproducible within the community. In other words, during the course of the project researchers train research participants in the application of the research instrument, allowing them not only to fully understand the results and underlying logic, but even conduct their own research in the future and more fully participate in the production of scientific knowledge.