In scientific research and
psychotherapy, the subject-expectancy effect, is a form of
reactivity that occurs when a
research subject expects a given result and therefore unconsciously affects the outcome, or reports the expected result. Because this effect can significantly
bias
Bias is a disproportionate weight ''in favor of'' or ''against'' an idea or thing, usually in a way that is closed-minded, prejudicial, or unfair. Biases can be innate or learned. People may develop biases for or against an individual, a group ...
the results of experiments (especially on
human subjects),
double-blind
In a blind or blinded experiment, information which may influence the participants of the experiment is withheld until after the experiment is complete. Good blinding can reduce or eliminate experimental biases that arise from a participants' expec ...
methodology is used to eliminate the effect.
Like the
observer-expectancy effect
The observer-expectancy effect (also called the experimenter-expectancy effect, expectancy bias, observer effect, or experimenter effect) is a form of reactivity in which a researcher's cognitive bias causes them to subconsciously influence t ...
, it is often a cause of "odd" results in many experiments. The subject-expectancy effect is most commonly found in
medicine
Medicine is the science and practice of caring for a patient, managing the diagnosis, prognosis, prevention, treatment, palliation of their injury or disease, and promoting their health. Medicine encompasses a variety of health care pr ...
, where it can result in the subject experiencing the
placebo effect
A placebo ( ) is a substance or treatment which is designed to have no therapeutic value. Common placebos include inert tablets (like sugar pills), inert injections (like Saline (medicine), saline), sham surgery, and other procedures.
In general ...
or
nocebo effect
A nocebo effect is said to occur when negative expectations of the patient regarding a treatment cause the treatment to have a more negative effect than it otherwise would have. For example, when a patient anticipates a side effect of a medicatio ...
, depending on how the influence pans out.
Example
An example of a scenario involving these various effects is as follows: A woman goes to her doctor with a problem. The doctor diagnoses with certainty, and then clearly explains the diagnosis and the expected route towards recovery. If he does this convincingly, calming her, removing fear and instilling hope, she will likely, through the positive expectancy, experience the placebo effect, aiding in her recovery.
On the other hand, if her doctor had had little time for her, was uncertain about the diagnosis, and had given her a
prescription, combined with a message along the lines of, "this may help sometimes", and added a message about possible horrible
side effects
In medicine, a side effect is an effect, whether therapeutic or adverse, that is secondary to the one intended; although the term is predominantly employed to describe adverse effects, it can also apply to beneficial, but unintended, consequence ...
(combined, say, with the patient having talked to a neighbor who also speaks along the same lines about the horrible side effects), then the chance of negative subject-expectancy, or
nocebo
A nocebo effect is said to occur when negative expectations of the patient regarding a treatment cause the treatment to have a more negative effect than it otherwise would have. For example, when a patient anticipates a side effect of a medicatio ...
, becomes quite large.
See also
*
Hawthorne effect
The Hawthorne effect is a type of reactivity in which individuals modify an aspect of their behavior in response to their awareness of being observed. The effect was discovered in the context of research conducted at the Hawthorne Western Electric ...
*
Pygmalion effect
The Pygmalion effect, or Rosenthal effect, is a psychological phenomenon in which high expectations lead to improved performance in a given area. The effect is named for the Greek myth of Pygmalion, the sculptor who fell so much in love with the ...
Bibliography
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{{DEFAULTSORT:Subject-Expectancy Effect
Cognitive biases