[1]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.
This variant of the phenomenon is named for the Hawthorne Works, a factory built by Western Electric, where efficiency engineers in the 1920s and 1930s were trying to determine if improved working conditions such as better lighting improved the performance of production workers.
The engineers noted that when they provided better working conditions in the production line, efficiency increased.
But when the engineers returned the production line to its original conditions and observed the workers, their efficiency increased again.
The engineers determined that it was merely the observation of the factory workers, not the changes in the conditions in production line, that increased the measured efficiency.