Observer's paradox
In the social sciences, the observer's paradox is a situation in which the phenomenon being observed is unwittingly influenced by the presence of the observer/investigator.
In linguistics
In the field of sociolinguistics, the term Observer’s Paradox was coined by William Labov, who stated with regard to the term:The aim of linguistic research in the community must be to find out how people talk when they are not being systematically observed; yet we can only obtain this data by systematic observation.
The term refers to the challenge sociolinguists face while doing fieldwork, where the task of gathering data on natural speech is undermined by the researcher's presence itself. As a field worker attempts to observe the daily vernacular of a speaker in an interview, the speaker, aware that their speech will be used for scholarly research, is likely to adopt a formal register. This produces data that is not representative of the speaker's typical speech, and the paradox lies in the fact that if the researcher was not present, the speaker would use normal vernacular.