The observer-expectancy effect (also called the experimenter-expectancy effect, observer effect, or experimenter effect) is a form of reactivity

Reactivity (psychology)

Reactivity is a phenomenon that occurs when individuals alter their performance or behavior due to the awareness that they are being observed. The change may be positive or negative, and depends on the situation. It is a significant threat to a research study's internal validity and is typically...

, in which a researcher

Researcher

A researcher is somebody who performs research, the search for knowledge or in general any systematic investigation to establish facts. Researchers can work in academic, industrial, government, or private institutions.-Examples of research institutions:...

's cognitive bias

Cognitive bias

A cognitive bias is a pattern of deviation in judgment that occurs in particular situations. Implicit in the concept of a "pattern of deviation" is a standard of comparison; this may be the judgment of people outside those particular situations, or may be a set of independently verifiable...

 causes them to unconsciously influence the participants of an experiment. It is a significant threat to a study's internal validity

Internal validity

Internal validity is the validity of inferences in scientific studies, usually based on experiments as experimental validity.- Details :...

, and is therefore typically controlled using a double-blind experimental design.

An example of the observer-expectancy effect is demonstrated in music backmasking

Backmasking

Backmasking is a recording technique in which a sound or message is recorded backward on to a track that is meant to be played forward...

, in which hidden verbal messages are said to be audible when a recording is played backwards. Some people expect to hear hidden messages when reversing songs, and therefore hear the messages, but to others it sounds like nothing more than random sounds. Often when a song is played backwards, a listener will fail to notice the "hidden" lyrics until they are explicitly pointed out, after which they are obvious

Confirmation bias

Confirmation bias is a tendency for people to favor information that confirms their preconceptions or hypotheses regardless of whether the information is true.David Perkins, a geneticist, coined the term "myside bias" referring to a preference for "my" side of an issue...

. Other prominent examples include facilitated communication

Facilitated communication

Facilitated communication is a process by which a facilitator supports the hand or arm of a communicatively impaired individual while using a keyboard or other devices with the aim of helping the individual to develop pointing skills and to communicate...

 and dowsing

Dowsing

Dowsing is a type of divination employed in attempts to locate ground water, buried metals or ores, gemstones, oil, gravesites, and many other objects and materials, as well as so-called currents of earth radiation , without the use of scientific apparatus...

.

See also

• Demand characteristics
  Demand characteristics
  In research, and particularly psychology, demand characteristics refers to an experimental artifact where participants form an interpretation of the experiment's purpose and unconsciously change their behavior accordingly. Pioneering research was conducted on demand characteristics by Martin Orne...
  
  
• Clever Hans
  Clever Hans
  Clever Hans was an Orlov Trotter horse that was claimed to have been able to perform arithmetic and other intellectual tasks....
  
   – a horse who seemed to be performing arithmetic
  Arithmetic
  Arithmetic or arithmetics is the oldest and most elementary branch of mathematics, used by almost everyone, for tasks ranging from simple day-to-day counting to advanced science and business calculations. It involves the study of quantity, especially as the result of combining numbers...
  
   and other amazing skills, but in reality took cues transmitted unconsciously by his trainer and observers.
• epistemic feedback
  Epistemic feedback
  The term "epistemic feedback" is a form of feedback which refers to an interplay between what is being observed and the result of the observation....
  
  
• Expectation
• Hawthorne effect
  Hawthorne effect
  The Hawthorne effect is a form of reactivity whereby subjects improve or modify an aspect of their behavior being experimentally measured simply in response to the fact that they know they are being studied, not in response to any particular experimental manipulation.The term was coined in 1950 by...
  
  
• Placebo
  Placebo
  A placebo is a simulated or otherwise medically ineffectual treatment for a disease or other medical condition intended to deceive the recipient...
  
   – an inert medicine or preparation which works because the patient thinks it will
• Nocebo
  Nocebo
  In medicine, a nocebo reaction or response refers to harmful, unpleasant, or undesirable effects a subject manifests after receiving an inert dummy drug or placebo...
  
  
• N-rays – imaginary radiation
• Pygmalion effect
  Pygmalion effect
  The Pygmalion effect, or Rosenthal effect, refers to the phenomenon in which the greater the expectation placed upon people, often children or students and employees, the better they perform...
  
   – teachers who expect higher achievement from some children actually get it
• Reality tunnel
  Reality tunnel
  Reality tunnel is a term coined by Timothy Leary and popularised by Robert Anton Wilson , akin to the idea of representative realism....
  
  
• Reflexivity (social theory)
  Reflexivity (social theory)
  Reflexivity refers to circular relationships between cause and effect. A reflexive relationship is bidirectional with both the cause and the effect affecting one another in a situation that does not render both functions causes and effects...
  
  
• Reference thinking
• Subject-expectancy effect
  Subject-expectancy effect
  The subject-expectancy effect, is a form of reactivity that occurs in scientific experiments or medical treatments when a research subject or patient expects a given result and therefore unconsciously affects the outcome, or reports the expected result...
  
  
• Naturalistic observation
  Naturalistic observation
  Naturalistic observation is a research tool in which a subject is observed in its natural habitat without any manipulation by the observer. During naturalistic observation researchers take great care to avoid interfering with the behavior they are observing by using unobtrusive methods...
  
  
• Participant observer

External links

• Skeptic's Dictionary on the Experimenter Effect
• An article that speaks of Expectancy effects in paranormal investigation
• Another article by Rupert Sheldrake
• Songs of Praise (With subtitles) An example of observer-expectancy effect involving subtitles which alter the observer's interpretation of audio.