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