A type of bias where one characteristic of a person or one factor in a situation affects the evaluation of the person's other traits.
Halo effect is a phenomenon that occurs when one is influenced by a person's strengths, weaknesses, physical appearance, behavior, or any other single factor. The halo effect is most often apparent in situations where one person is responsible for evaluating or assessing another in some way. Examples of such situations include assessment of applicants for jobs, scholarships, or awards; designating job or committee assignments based on perceived capabilities or past performance; and in evaluating academic, job, or athletic performance. The halo effect can undermine an individual's effort to be objective in making judgments because all people respond to others in a variety of ways, making true objectivity nearly impossible. However, the halo effect causes one characteristic or quality of an individual to override all others.
To counteract the halo effect, decision makers can break the evaluation process into specific steps, evaluating only one characteristic at a time, but human judgments can never be free of complex influences.
The term "halo effect" describes what happens when a scientific observation is influenced by the observer's perceptions of the individual, procedure, or service that is under observation. The observer's prejudices, recollections of previous observations, and knowledge about prior observations or findings can all affect objectivity and must be guarded against. The term also describes the effect, usually beneficial, that a health care provider's manner, attention, and care have on a sick person, regardless of the nature of the service or the procedure involved. This is a variation of the placebo effect, though it differs from the placebo effect in being associated with the personality of the service provider rather that with the service or regimen as such.
John M. Last
(see also: Hawthorne Effect; Observational Studies )