In fields such as anthropology, behavioral biology and ecology, watching a person or organism in a natural environment is essential.
Most naturalistic observation is unobtrusive, such as a researcher setting up a camera to film the behavior of a badger underground. Most nature documentaries are examples of naturalistic observational study, where days, weeks or even years of film are analyzed and edited, to give an overview of the life cycle of the organism.
There is often little attempt at analysis, quantitative or qualitative, but the observational study does uncover unknown phenomena and behaviors.
Obtrusive naturalistic observational study is often used in anthropology, where a researcher lives with a remote tribe for a period of time and records their behavior. By living there, she is influencing their social interactions and habits, but can still make some excellent observations.
Often, anthropologists will adopt the lifestyle of a particular group of people, in an attempt to understand why they have certain customs and beliefs.
In technical terms, it would be difficult to follow people without discovery, and it would also be unethical to observe without consent, so obtrusive naturalistic observation is the only method that can be used with human subjects.
Many of the producers of the recent glut of reality shows try to claim that their shows are psychological experiments, based around observational study. This is stretching the idea too far, as there are very few people who would not change their behavior when they are aware that a camera is watching.
In these cases, it is difficult to make any realistic and valid observations about their lifestyle.
Most criticisms of naturalistic observation are based around this principle, and an anthropologist or social scientist has to ensure that they intervene as little as possible.
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Goodwin, C.J. (2009). Research in Psychology: Methods and Design. Hoboken, NJ: John Wiley
Jackson, S.L. (2011). Research Methods and Statistics: A Critical Thinking Approach (2nd Ed.). Belmont, CA: Wadsworth Cengage Learning