Field research turns people from answers on a form into observed participants in a world.
The problem with asking people what they want is that people can only report what they can notice, remember, and comfortably say. Their stated preferences may be sincere and still fail to explain their actual choices. Field research closes part of that gap by studying people in the settings where their habits, language, relationships, and decisions actually occur.
In its strongest form, field research combines direct observation with open-ended interviews and attention to the surrounding environment. Ethnography is one important form: the researcher enters a social or cultural setting, participates carefully enough to gain an insider’s perspective, and builds an account from observation, interviews, documents, and artifacts. The field is not a warehouse of neutral facts. The way a researcher enters, asks, listens, and interprets changes what becomes visible.
This is why the method matters in advertising. A respondent may describe themselves as rational, independent, or price-sensitive, while their routines reveal a different structure of desire, status, fear, convenience, and imitation. Field research does not make the researcher omniscient. It makes the distance between what people say and what they do available for analysis.
Source: SAGE Research Methods, “Ethnography” and “Ethnographic Methods: Ethnography: Theory and Methods.” Academic reference sources, not peer-reviewed journal articles.