Subject-expectancy effect
Encyclopedia
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. Because this effect can significantly bias
the results of experiments (especially on human subjects), double-blind
methodology is used to eliminate the effect.
Like the observer-expectancy effect
, it is often a cause of "odd" results in many experiments. The subject-expectancy effect is most commonly found in medicine
, where it can result in the subject experiencing the placebo effect
or nocebo effect, depending on how the influence pans out.
An example of a scenario involving these various effects is as follows: A woman goes to her doctor with an issue. 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
(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, becomes quite large.
The subject expectancy effect is also clearly seen in psychotherapy
.
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...
that occurs in scientific experiments or medical treatments when a research subject or patient
Patient
A patient is any recipient of healthcare services. The patient is most often ill or injured and in need of treatment by a physician, advanced practice registered nurse, veterinarian, or other health care provider....
expects a given result and therefore unconsciously affects the outcome, or reports the expected result. Because this effect can significantly bias
Bias
Bias is an inclination to present or hold a partial perspective at the expense of alternatives. Bias can come in many forms.-In judgement and decision making:...
the results of experiments (especially on human subjects), double-blind
Double-blind
A blind or blinded experiment is a scientific experiment where some of the people involved are prevented from knowing certain information that might lead to conscious or subconscious bias on their part, invalidating the results....
methodology is used to eliminate the effect.
Like the observer-expectancy effect
Observer-expectancy effect
The observer-expectancy effect is a form of reactivity, in which a researcher's cognitive bias causes them to unconsciously influence the participants of an experiment...
, it is often a cause of "odd" results in many experiments. The subject-expectancy effect is most commonly found in medicine
Medicine
Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....
, where it can result in the subject experiencing the placebo effect
Placebo effect
Placebo effect may refer to:* Placebo effect, the tendency of any medication or treatment, even an inert or ineffective one, to exhibit results simply because the recipient believes that it will work...
or nocebo effect, depending on how the influence pans out.
An example of a scenario involving these various effects is as follows: A woman goes to her doctor with an issue. 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
Medical prescription
A prescription is a health-care program implemented by a physician or other medical practitioner in the form of instructions that govern the plan of care for an individual patient. Prescriptions may include orders to be performed by a patient, caretaker, nurse, pharmacist or other therapist....
, combined with a message along the lines of, "this may help sometimes," and added a message about possible horrible side effects
Side Effects
Side Effects is an anthology of 17 comical short stories written by Woody Allen between 1975 and 1980, all but one of which were previously published in, variously, The New Republic, The New York Times, The New Yorker, and The Kenyon Review. It includes Allen's 1978 O...
(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, becomes quite large.
The subject expectancy effect is also clearly seen in psychotherapy
Psychotherapy
Psychotherapy is a general term referring to any form of therapeutic interaction or treatment contracted between a trained professional and a client or patient; family, couple or group...
.