Expectancy Effect
The subject-expectancy effect attributes the placebo effect to conscious or unconscious manipulation by patients in reporting improvement. Hróbjartsson and Götzsche argued in their article, "Most patients are polite and prone to please the investigators by reporting improvement, even when no improvement was felt." Subjective bias can also be unconscious, where the patient believes he is improving as a result of the attention and care he has received.
[edit] Conditioning
Classical conditioning is a type of associative learning where the subject learns to associate a particular stimulus with a particular response. In this case the stimulant is the substance perceived as medicine but is the placebo, and the response is the relief of symptoms. It is difficult to tell the difference between conditioning and the expectancy effect when the outcome is subjective and reported by the patient. However, conditioning can result in measurable biological changes similar to the changes seen with the real treatment or drug. For example, studies showing that placebo treatments result in changes in brain function similar to the real drug are probably examples of conditioning resulting in objectively measurable results. (Sauro 2005, Wager 2004, Leuchter 2002)
[edit] Motivation
Motivational explanations of the placebo effect have typically considered the placebo effect to be an outcome of one’s desire to feel better, reduce anxiety, or cooperate with an experimenter or health care professional (Price et al. 1999, Margo 1999). The motivational perspective is supported by recent research showing that nonconscious goals for cooperation can be satisfied by confirming expectations about a treatment (Geers et al. 2005).[/b]
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